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Xid-associated resistance to experimental Chagas' disease is IFN-γ dependent
Abstract
In contrast to normal Balb/c, Balb.Xid immunodeficient mice are naturally resistant to Trypanosoma cruzi infection. Thus, Balb.Xid mice control parasitemia, do not show the characteristic wasting in the acute infection and develop no tissue pathology in the skeletal or cardiac muscles in the chronic phase of disease. By in situ hybridization and semiquantitative polymerase chain reaction, the expression of IL genes in spleen cells from Balb/c and Balb.Xid mice were compared after T. cruzi infection. The results showed that Balb.Xid mice produce considerably higher levels of IFN-gamma, IL-2, and IL-4, but lower levels of IL-10, from as early as 4 days after parasite injection. By day 12 of the infection, although IFN-gamma, IL-2, and IL-4 expression was now comparable in both groups, IL-10 levels continue to be lower in Balb.Xid than in control Balb/c animals. The central role of IFN-gamma in the resistance to T. cruzi was confirmed by treatment of Balb.Xid mice with anti-IFN-gamma antibodies that reestablished susceptibility and lead to increased parasitemia and mortality.
... When infected, these animals demonstrate a progressive inflammatory response that is mediated by the production of pro-inflammatory molecules and decreased production of IL-10. These characteristics have been observed during infection by Paracoccidioides brasiliensis (Popi et al., 2008), Filaria (Mukhopadhyay et al., 1999), Leishmania (Arcanjo et al., 2017), and Trypanosoma cruzi (Minoprio et al., 1993). ...
... In addition to subverting the microbicidal mechanisms by the parasite, it is possible that endogenous factors such as the production of modulating cytokines are partly responsible for the success of the infection (Dutra et al., 2014;Luna-Gomes et al., 2014;Decote-Ricardo et al., 2017;Mendonca et al., 2017). In T. cruzi infection, XID animals exhibit a decrease in IL-10 production and favor the production of IFN-γ and IL-2, which may be determinants in the control of parasitism (Minoprio et al., 1993). This information suggests an increased susceptibility of macrophages in the presence of B-1 cells. ...
... Statistical analysis was performed by t-test from representative results of three similar experiment ( * p < 0.05 and * * p < 0.01). susceptibility or resistance in models of infection (Minoprio et al., 1993;Popi et al., 2008;Arcanjo et al., 2017). These immunomodulatory effects were observed in different models involving infection and inflammation (Oliveira et al., 2010;Arcanjo et al., 2015;Gambero et al., 2016;Aziz et al., 2017). ...
B-1 cells can directly and indirectly influence the immune response. These cells are known to be excellent producers of natural antibodies and can secrete a variety of immunomodulatory molecules. They are also able to differentiate into B-1 cell-derived phagocytes (B-1CDP). B-1 cells can modulate macrophages to become less effective, and B-1CDP cells are more susceptible in infection models. In this work, we investigated the microbicidal ability of these cells in Trypanosoma cruzi infection in vitro. The results show that macrophages from BALB/c mice are more susceptible to infection than macrophages from XID mice. The resistance observed in macrophages from XID mice was abolished in the presence of B-1 cells, and this event seems to be associated with IL-10 production by B-1 cells, which may have contributed to the decrease of NO production. Additionally, B-1CDP cells were more permissive to intracellular T. cruzi infection than peritoneal macrophages. These findings strongly suggest that B-1 cells and B-1CDP cells have a potential role in the persistence of the parasite in host cells.
... On the other hand, XID mice infected with Trypanosoma cruzi exhibited low levels of specific and non-specific immunoglobulins in serum, and were able to control parasitemia in comparison to the control (Minoprio et al. 1993). Analysis of mRNA transcripts in the spleen of infected animals showed that XID mice produced high mRNA levels of mRNA for IFN-γ, IL-2, and IL-4, and low mRNA levels of IL-10 after 4 days of infection. ...
... Analysis of mRNA transcripts in the spleen of infected animals showed that XID mice produced high mRNA levels of mRNA for IFN-γ, IL-2, and IL-4, and low mRNA levels of IL-10 after 4 days of infection. The administration of anti-IFN-γ in XID led to an increase in parasitemia, demonstrating the important role of IFN-γ in these animals as one of the factors associated with parasite resistance (Minoprio et al. 1993). ...
... In addition, peritoneal B-1 cells proliferated and secreted large amounts of IL-10 after stimulation with carbohydrate antigens from S. mansoni egg, but the mechanisms and the receptors involved in these responses are not yet clear (Velupillai et al. 1997). Trypanosoma cruzi Susceptibility Production of cytokines* and differentiation into plamocytes Minoprio et al. (1993) and Merino et al. (2010) Although the use of XID mice to study B-1 cells is somewhat limited, since defects in other B cell populations are also found in these animals, several studies using the adoptive transfer of B-1 cells to these animals corroborated the findings in XID animals. The effects caused by the absence of these cells were total or partial reversed after the adoptive transfer of B-1 cell to XID mice. ...
The peritoneal cavity has a microenvironment capable of promoting proliferation, differentiation, and activation of the resident cells and recruitment of blood cells through the capillary network involved in the peritoneum. Among the cells found in the peritoneal cavity, B-1 cells are a particular cell type that contains features that are not very well defined. These cells differ from conventional B lymphocytes (B-2) by phenotypic, functional, and molecular characteristics. B-1 cells can produce natural antibodies, migrate to the inflammatory focus, and have the ability to phagocytose pathogens. However, the role of B-1 cells in immunity against parasites is still not completely understood. Several experimental models have demonstrated that B-1 cells can affect the susceptibility or resistance to parasite infections depending on the model and species. Here, we review the literature to provide information on the peculiarities of B-1 lymphocytes as well as their interaction with parasites.
... There is indirect evidence of the regulatory role of B cells in the development of the immune response against T. cruzi. Although there are some discrepancies, most of the evidence supports the idea that both, partial (Xid mouse) and absolute (mMT mouse) deficiencies in B cells generate important outcomes in the development of the infection, generally associated with a stronger inflammatory response presenting higher levels of IFNg, IL-6, IL-18 and TNFa in serum (Minoprio et al., 1993;Cardillo et al., 2007;Gorosito Serrań et al., 2017;da Rocha et al., 2019). In the mMT mouse absolute depletion model, Gorosito Serrań et al. demonstrate that the increased of infected animals mortality was associated with an unconventional CD4 + T cell exacerbated response leading to an uncontrolled immune response and increased inflammation (Gorosito Serrań et al., 2017). ...
... In T. cruzi infection, previous works with B cell-depleted Xid or µMT mice provided evidence supporting that B cells can regulate the T cell response (Minoprio et al., 1993;Gorosito Serrań et al., 2017;Fiocca Vernengo et al., 2020). However, the mechanisms and cell populations involved in the T CD4 + modulation process are still not understood. ...
Trypanosoma cruzi infection induces a polyclonal B cell proliferative response characterized by maturation to plasma cells, excessive generation of germinal centers, and secretion of parasite-unrelated antibodies. Although traditionally reduced to the humoral response, several infectious and non-infectious models revealed that B lymphocytes could regulate and play crucial roles in cellular responses. Here, we analyze the trypomastigote-induced effect on B cells, their effects on CD4⁺ T cells, and their correlation with in vivo findings. The trypomastigotes were able to induce the proliferation and the production of IL-10 or IL-6 of naïve B cells in co-culture experiments. Also, we found that IL-10-producing B220lo cells were elicited in vivo. We also found up-regulated expression of FasL and PD-L1, proteins involved in apoptosis induction and inhibition of TCR signaling, and of BAFF and APRIL mRNAs, two B-cell growth factors. Interestingly, it was observed that IL-21, which plays a critical role in regulatory B cell differentiation, was significantly increased in B220⁺/IL-21⁺ in in vivo infections. This is striking since the secretion of IL-21 is associated with T helper follicular cells. Furthermore, trypomastigote-stimulated B-cell conditioned medium dramatically reduced the proliferation and increased the apoptotic rate on CD3/CD28 activated CD4⁺ T cells, suggesting the development of effective regulatory B cells. In this condition, CD4⁺ T cells showed a marked decrease in proliferation and viability with marginal IL-2 or IFNγ secretion, which is counterproductive with an efficient immune response against T. cruzi. Altogether, our results show that B lymphocytes stimulated with trypomastigotes adopt a particular phenotype that exerts a strong regulation of this T cell compartment by inducing apoptosis, arresting cell division, and affecting the developing of a proinflammatory response.
... These results indicate a potentiation of the anti-parasitic activity in B-1 cell-deficient BALB/XID mice. The role of B-1 cells in protective mediatedimmunity of the host depends on the nature of the pathogen as well as the infection experimental models (Minoprio et al., 1993;Hoerauf et al., 1994;Babai et al., 1999;Gaubert et al., 1999;Herbert et al., 2002;Popi et al., 2008;Crane et al., 2013;Szymczak et al., 2013;Gonzaga et al., 2015). Intracelular parasites such as Trypanosoma cruzi and Francisella tularensis that target macrophage cells are susceptible to negative modulation of the mononuclear phagocyte system by B-1 cells (Minoprio et al., 1993;Crane et al., 2013). ...
... The role of B-1 cells in protective mediatedimmunity of the host depends on the nature of the pathogen as well as the infection experimental models (Minoprio et al., 1993;Hoerauf et al., 1994;Babai et al., 1999;Gaubert et al., 1999;Herbert et al., 2002;Popi et al., 2008;Crane et al., 2013;Szymczak et al., 2013;Gonzaga et al., 2015). Intracelular parasites such as Trypanosoma cruzi and Francisella tularensis that target macrophage cells are susceptible to negative modulation of the mononuclear phagocyte system by B-1 cells (Minoprio et al., 1993;Crane et al., 2013). In fact these cells can be programmed to differentiate into phagocytes (Popi et al., 2012) that could promote immunosurveillance in the different tissues affected by the parasitism thus contributing to the outcome of infection. ...
Visceral leishmaniasis is a neglected disease caused by Leishmania protozoa parasites transmitted by infected sand fly vectors. This disease represents the second in mortality among tropical infections and is associated to a profound immunosuppression state of the host. The hallmark of this infection-induced host immunodeviation is the characteristic high levels of the regulatory interleukin-10 (IL-10) cytokine. In the present study, we investigated the role of B-1 cells in the maintenance of splenic IL-10 levels that could interfere with resistance to parasite infection. Using an experimental murine infection model with Leishmania (L.) infantum chagasi we demonstrated an improved resistance of B-1 deficient BALB/XID mice to infection. BALB/XID mice developed a reduced splenomegaly with diminished splenic parasite burden and lower levels of IL-10 secretion of purified splenocytes at 30 days post-infection, as compared to BALB/c wild-type control mice. Interestingly, we found that resident peritoneal macrophages isolated from BALB/XID mice were more effective to control the parasite load in comparison to cells isolated from BALB/c wild-type mice. Our findings point to a role of B-1 cells in the host susceptibility to visceral leishmaniasis.
... IFN-γ is critical for the control of T. cruzi in mammals. Susceptibility to T. cruzi infection is significantly increased in mice treated with anti-IFN-γ antibodies as well as mice lacking IFN-γ (72)(73)(74)(75)(76)(77)(78). Additionally, infected mice respond to IFN-γ administration with enhanced parasite clearance and increased survival as compared to non-treated infected mice (79,80). ...
... Thus, the absence of IFN-γ during T. cruzi infection did not result in a complete loss of chemokine expression nor chemokine receptor expression, though expression of specific chemokines and chemokine receptors was significantly delayed or reduced.DiscussionThis study examined the chemokine receptors that are expressed on activated T cells in muscle tissue as well as the effect of IFN-γ on expression of these receptors during T. cruzi infection. IFN-γ is critical for the control of T. cruzi in mammals; mice treated with anti-IFN-γ antibodies and mice lacking IFN-γ are highly susceptible to early death from T. cruzi infection(72)(73)(74)(75)(76)(77)(78). Additionally, T. cruzi infected mice respond to IFN-γ administration with enhanced parasite clearance and increased survival as compared to non-treated infected mice(79,80).Among the many properties of IFN-γ is the induction of T cell attracting chemokines(64,102,103), including IP-10 an essential chemokine for the recruitment of both CD4 + and CD8 + T cells in Toxoplasma gondii infection and likely plays a similar role in T. cruzi infected tissues(101). ...
Immune control of Trypanosoma cruzi, the causative agent of Chagas disease, requires the cytokine interferon-γ. The mechanism by which interferon-γ acts in control of infection is investigated here. Among the effector functions induced by interferon-γ is production of the microbicidal agent nitric oxide (NO) and other proteins that guide effector cells to sites of infection. While there is evidence to support a role for NO in control of T. cruzi infection, this study demonstrates that NO is not absolutely required for survival in T. cruzi infection. The increased production of certain cytokines by infected NO-deficient mice may compensate for the lack of NO and therefore contribute to the control of T. cruzi infection. Additionally, interferon-γ mediates recruitment of effector cells to infection sites by induction of chemokine ligands and chemokine receptors. In the absence of IFN-γ such recruitment is significantly delayed. Nitric oxide production and chemokine and chemokine receptor expression are part of a network of IFN-γ inducible responses that collectively contribute to the control T. cruzi infection.
... Fas/FasL mediated apoptosis of parasite specific B cells and immature B cells in the bone marrow (BM) has also been reported in Balb/c mice (Zuniga, Motran et al. 2000;Zuniga, Motran et al. 2002;Zuniga, Acosta-Rodriguez et al. 2005). Studies in Balb/c XID mice showed that the depletion of B cell subsets in this model led to an increased resistance to disease that was associated with improved IFN-γ responses, decreased hypergammaglobulinemia, and a skewed natural antibody repertoire (Minoprio, Coutinho et al. 1991;Minoprio, el Cheikh et al. 1993;Santos-Lima, Vasconcellos et al. 2001). Limited studies of B cell dynamics during T. cruzi infection in resistant versus susceptible mice have been reported (d'Imperio Lima, Eisen et al. 1986;Minoprio, Eisen et al. 1986). ...
... Analysis of circulating cytokines post-infection confirmed the skewing of Balb/c mice toward Th2 responses and the C57BL/6 mice toward Th1 responses (Fig 3). These data are in agreement with previous reports that early Th1 IFN-γ responses are associated with resistance to infection (Antunez and Cardoni 2000;Hoft, Schnapp et al. 2000) and that Th2 cytokines, especially IL-4 and IL-10 are associated with susceptibility to infection (Minoprio, el Cheikh et al. 1993;Barbosa de Oliveira, Curotto de Lafaille et al. 1996;Hiyama, Hamano et al. 2001;Kumar and Tarleton 2001;Muller, Kohler et al. 2001; Acosta-Rodriguez, Montes et al. 2004;Vogt, Alba Soto et al. 2008). The results of the present study show that early Th1-skewed cytokine burst was coincident with control of parasitemia and preceded the generation of parasite-specific humoral immunity in resistant C57Bl/6 mice ( Fig. 9). ...
The etiologic agent of Chagas' disease is Trypanosoma cruzi. Patent parasitemia leads to parasite spread throughout the host during acute phase disease. Parasitemia concomitant with polyclonal lymphocyte activation has been reported and is thought to contribute to parasite evasion of host immunity and subsequent parasite persistence, which leads to chronic disease. In the present studies, polyclonal B cell activation was evaluated in relatively susceptible Balb/c versus resistant C57Bl/6 mouse models. Hypergammaglobulinemia and B cell activation in susceptible mice was associated with a large number of antibody secreting cells (ASC) without appreciable parasite-specific ASC. In contrast, in resistant mice, B cell activation and expansion was associated with generation of parasite-specific humoral immunity. These data indicate that the outcome of B cell activation during early T. cruzi experimental infection varies according to host susceptibility. T. cruzi encodes several proteins with mitogenic capacities that are thought to contribute to dysfunctional polyclonal B cell activation in susceptible mice. One recently identified T. cruzi mitogen is a proline racemase (TcPRAC). Characterization of B cell activation by recombinant protein in this study demonstrates that TcPRAC induced polyclonal B cell activation, evident by proliferation, antibody secretion, IL-10 production, and B cell surface phenotype. MZ B cells were more responsive to T-cell independent TcPRAC stimulation than were follicular mature (FM) B cells. These data provide the first comprehensive characterization of B cell activation by TcPRAC. During experimental T. cruzi infection, TcPRAC-specific IgG remained undetectable. Conversely, intradermal genetic immunization via gene-gun (GG) induced antigen-specific immunogenic responses, generating TcPRAC-specific high-titer IgG, bone marrow plasma cells, and memory B cells. TcPRAC-specific IgG bound mitogenic rTcPRAC, decreasing subsequent B cell activation. GG immunization with TcPRAC DNA was non-mitogenic and did not effect generation of specific IgG to another T. cruzi antigen, complement regulatory protein (CRP). These data demonstrate the utility of genetic immunization for the conversion of a protein mitogen into an effective immunogen. Furthermore, co-immunization of TcPRAC with another T. cruzi antigen indicated the usefulness of this approach for multivalent vaccine development.
... For T. congolense, evidence suggests that genomic imprinting controls Tir1, a major locus involved in mouse susceptibility to the parasite [38]. Finally, in the case of T. cruzi, it has been shown that an X-linked mutation of Balb.Xid immunodeficient mice influences murine resistance to infection, this process may be dependent on the increased production of IFN-c, which possibly account for the increased resistance of the BALB.XID as compared to Balb/c mouse [32,39]. Accordingly, the effect of sex has also been reported to be important for susceptibility to Chagas disease, both in mouse and human infection [16,22,32,[39][40][41]. ...
... Finally, in the case of T. cruzi, it has been shown that an X-linked mutation of Balb.Xid immunodeficient mice influences murine resistance to infection, this process may be dependent on the increased production of IFN-c, which possibly account for the increased resistance of the BALB.XID as compared to Balb/c mouse [32,39]. Accordingly, the effect of sex has also been reported to be important for susceptibility to Chagas disease, both in mouse and human infection [16,22,32,[39][40][41]. ...
Chagas disease develops upon infection with the protozoan parasite Trypanosoma cruzi and undergoes an acute phase characterized by massive parasite replication and the presence of parasites in the blood. This condition is known as acute phase parasitemia. This initial stage may result in a cure, in the development of the chronic stages of the disease or in the death of the infected host. Despite intensive investigation related to the characterization of the acute and chronic phases of the disease, the cause-effect relationship of acute phase parasitemia to the outcome of the disease is still poorly understood. In this study, we artificially generated a heterogeneously controlled mouse population by intercrossing F1 mice obtained from a parental breeding of highly susceptible A/J with highly resistant C57BL/6 mouse strains. This F2 population was infected and used to assess the correlation of acute phase parasitemia with the longevity of the animals. We used nonparametric statistical analyses and found a significant association between parasitemia and mortality. If males and females were evaluated separately, we found that the former were more susceptible to death, although parasitemia was similar in males and females. In females, we found a strong negative correlation between parasitemia and longevity. In males, however, additional factors independent of parasitemia may favor mouse mortality during the development of the disease. The correlations of acute phase parasitemia with mortality reported in this study may facilitate an appropriate prognostic approach to the disease in humans. Moreover, these results illustrate the complexity of the mammalian genetic traits that regulate host resistance during Chagas disease.
... Fas/FasL mediated apoptosis of parasite specific B cells and immature B cells in the bone marrow (BM) has also been reported in Balb/c mice [30,31,32]. Studies in Balb/ c XID mice show that the depletion of B cell subsets in this model led to an increased resistance to disease that was associated with improved IFN-c responses, decreased hypergammaglobulinemia, and a skewed natural antibody repertoire [33,34,35]. Limited studies of B cell dynamics during T. cruzi infection in resistant versus susceptible mice have been reported [20,28]. ...
... Analysis of circulating cytokines post-infection confirmed the skewing of Balb/c mice toward Th2 responses and the C57BL/6 mice toward Th1 responses (Fig 3). These data are in agreement with previous reports that early Th1 IFN-c responses are associated with resistance to infection [50,78] and that Th2 cytokines, especially IL-4 and IL-10 are associated with susceptibility to infection [34,79,80,81,82,83,84]. The results of the present study show that early Th1-skewed cytokine burst was coincident with control of parasitemia and preceded the generation of parasite-specific humoral immunity in resistant C57Bl/6 mice (Fig. 9). ...
Background:
The etiologic agent of Chagas Disease is Trypanosoma cruzi. Acute infection results in patent parasitemia and polyclonal lymphocyte activation. Polyclonal B cell activation associated with hypergammaglobulinemia and delayed specific humoral immunity has been reported during T. cruzi infection in experimental mouse models. Based on preliminary data from our laboratory we hypothesized that variances in susceptibility to T. cruzi infections in murine strains is related to differences in the ability to mount parasite-specific humoral responses rather than polyclonal B cell activation during acute infection.
Methodology/principal findings:
Relatively susceptible Balb/c and resistant C57Bl/6 mice were inoculated with doses of parasite that led to similar timing and magnitude of initial parasitemia. Longitudinal analysis of parasite-specific and total circulating antibody levels during acute infection demonstrated that C57Bl/6 mice developed parasite-specific antibody responses by 2 weeks post-infection with little evidence of polyclonal B cell activation. The humoral response in C57Bl/6 mice was associated with differential activation of B cells and expansion of splenic CD21(high)CD23(low) Marginal Zone (MZ) like B cells that coincided with parasite-specific antibody secreting cell (ASC) development in the spleen. In contrast, susceptible Balb/c mice demonstrated early activation of B cells and early expansion of MZ B cells that preceded high levels of ASC without apparent parasite-specific ASC formation. Cytokine analysis demonstrated that the specific humoral response in the resistant C57Bl/6 mice was associated with early T-cell helper type 1 (Th1) cytokine response, whereas polyclonal B cell activation in the susceptible Balb/c mice was associated with sustained Th2 responses and delayed Th1 cytokine production. The effect of Th cell bias was further demonstrated by differential total and parasite-specific antibody isotype responses in susceptible versus resistant mice. T cell activation and expansion were associated with parasite-specific humoral responses in the resistant C57Bl/6 mice.
Conclusions/significance:
The results of this study indicate that resistant C57Bl/6 mice had improved parasite-specific humoral responses that were associated with decreased polyclonal B cell activation. In general, Th2 cytokine responses are associated with improved antibody response. But in the context of parasite infection, this study shows that Th2 cytokine responses were associated with amplified polyclonal B cell activation and diminished specific humoral immunity. These results demonstrate that polyclonal B cell activation during acute experimental Chagas disease is not a generalized response and suggest that the nature of humoral immunity during T. cruzi infection contributes to host susceptibility.
... An especially interesting finding is that the CD5 + B cell subsets may have multiple regulatory properties including: constitutive FasL and PD-L2 expression, and a propensity to produce IL-10 upon activation by bacterial and parasitic antigens [48,71,86,103,108]. The unique tissue distribution, antibody production, and evidence of immune deviation found in mice lacking CD5 + B cells suggest that these cells may play an important role in controlling mucosal immune reactions and autoimmunity [27,47,62]. ...
... Studies of other parasitic infections in XID mice have also confirmed that B cells are important producers of IL-10 and regulators of T cell activation [4,62,71]. Some reports have shown that infection with T. cruzi stimulates antigen-specific B cells to express FasL and results in increased B cell apoptosis [111]. ...
Immune regulation plays a critical role in controlling potentially dangerous inflammation and maintaining health. The Fas ligand/Fas receptor axis has been studied extensively as a mechanism of killing T cells and other cells during infections, autoimmunity, and cancer. FasL expression has been primarily attributed to activated T cells and NK cells. Evidence has emerged that B lymphocytes can express FasL and other death-inducing ligands, and can mediate cell death under many circumstances. Among B cell subsets, the expression of both Fas ligand and IL-10 is highest on the CD5(+) B cell population, suggesting that CD5(+) B cells may have a specialized regulatory function. The relevance of killer B cells to normal immune regulation, disease pathogenesis, and inflammation is discussed.
... However, T cell-dependent B cell responses are also reduced and the total number of B cells decreased, resulting in IgM and IgG3 hypogammaglobulinemia (9,(13)(14)(15). Interestingly, mice carrying the xid mutation are resistant to many autoimmune diseases (16,17) and parasitic infections (18)(19)(20). ...
... Since IL-10 down-regulates production of IFN-y, decreased synthesis of IL-10 in xid mice could lead to exaggerated secretion of IFN-y. This assumption has been suggested by several recent studies dealing with experimental parasitic infections (18)(19)(20). We did not find any difference in IL-10 mRNA expression by spleen cells between xid and control mice. ...
To investigate the role of B cells in the development of experimental Staphylococcus aureus-induced arthritis, we used X-linked immunodeficiency (xid) mice that carry a Bruton's tyrosine kinase mutation affecting the function of B cells. NFR/N.xid and congenic NFR/N mice were inoculated i.v. with a toxic syndrome toxin-1 producing S. aureus LS-1 strain. B cell-deficient NFR/N.xid mice developed less frequent (p < 0.01) and less severe (p < 0.01) arthritis than NFR/N mice did. These clinical findings were corroborated by histopathologic evaluation, indicating that NFR/N.xid mice had significantly lower (p < 0.01) erosivity of the disease. Interestingly, infected NFR/N.xid mice showed decreased bacterial burden in blood, joints, and other organs compared with the control mice. Serologic studies displayed poor B cell responses to staphylococcal cell walls, toxic shock syndrome toxin-1, and ssDNA, accompanied by a low level of Igs in infected NFR/N.xid mice. More importantly, xid defect affected cytokine profile. The in vitro experiments showed that the lymphocytes from NFR/N.xid mice had low IL-6, but high IFN-gamma production upon stimulation with staphylococcal cell walls compared with NFR/N mice. Furthermore, the in situ hybridization technique revealed the relative increase of IFN-gamma, but marked decrease of IL-1 beta mRNA expression in spleens of infected NFR/N.xid mice. No significant difference in IL-4, IL-10, and TNF-alpha mRNA expression was found between both strains. Our findings demonstrate that B cells may, directly or indirectly, contribute to the pathogenesis of septic arthritis. The results indicate that increased IFN-gamma production along with low IL-6 and IL-1 beta synthesis found in xid mice may provide a more favorable outcome of S. aureus arthritis.
... Unlike the findings of this study, which evidenced a protective role for B1 B-cells cells in chronic Chagas disease, previous studies in experimental models have demonstrated that CD5 + B-cells contribute to pathology (64,65). More recently, it was shown that murine B1 B-cells can be classified into B1a and B1b according with the expression (CD5 + ) or lack (CD5 − ) of cell surface protein (66). ...
B-cells mediate humoral adaptive immune response via the production of antibodies and cytokines, and by inducing T-cell activation. These functions can be attributed to distinct B-cell subpopulations. Infection with Trypanosoma cruzi, the causative agent of Chagas disease, induces a polyclonal B-cell activation and lytic antibody production, critical for controlling parasitemia. Individuals within the chronic phase of Chagas disease may remain in an asymptomatic form (indeterminate), or develop severe cardiomyopathy (cardiac form) that can lead to death. Currently, there is no effective vaccine to prevent Chagas disease, and no treatment to halt the development of the cardiomyopathy once it is installed. The pathology associated with cardiac Chagas disease is a result of an inflammatory reaction. Thus, discovering characteristics of the host's immune response that favor the maintenance of favorable heart function may unveil important immunotherapeutic targets. Given the importance of B cells in antibody production and parasite control, we investigated T. cruzi-derived antigenic fractions responsible for B-cell activation and whether frequencies and functional characteristics of B-cell subpopulations are associated with different clinical outcomes of human Chagas disease. We stimulated cells from indeterminate (I) and cardiac (C) Chagas patients, as well as non-infected individuals (NI), with T. cruzi-derived protein- (PRO), glycolipid- (GCL) and lipid (LIP)-enriched fractions and determined functional characteristics of B-cell subpopulations. Our results showed that the frequency of B-cells was similar amongst groups. PRO, but not GCL nor LIP, led to an increased frequency of B1 B-cells in I, but not C nor NI. Although stimulation with PRO induced higher TNF expression by B1 B-cells from C and I, as compared to NI, it induced expression of IL-10 in cells from I, but not C. Stimulation with PRO induced an increased frequency of the CD11b⁺ B1 B-cell subpopulation, which was associated with better cardiac function. Chagas patients displayed increased IgM production, and activation of gamma-delta T-cells, which have been associated with B1 B-cell function. Our data showed that PRO activates CD11b⁺ B1 B-cells, and that this activation is associated with a beneficial clinical status. These findings may have implications in designing new strategies focusing on B-cell activation to prevent Chagas disease cardiomyopathy.
... Also, increased Th1 response was found in other lymphoid tissues of the mutants. Previous studies reported that BTK-deficient mice were resistant to parasite infections 29,30 , possibly through mounting a higher Th1 response. Frequent development of Th1-related autoimmune diseases has also been reported for XLA patients 31 . ...
Inflammatory bowel disease (IBD) is driven by multiple genetic and environmental risk factors. Patients with mutations in Bruton’s tyrosine kinase (BTK) is known to manifest high prevalence of intestinal disorders including IBD. Although BTK mediates the signaling of various immune receptors, little is known how BTK maintains the homeostasis of the gut immune system. Here, we show that BTK-deficiency promotes IBD progression in a mouse model of colitis. Interestingly, the increased colitis susceptibility of BTK-deficient mice is not caused by gut microbiota changes but rather arises from enhanced pro-inflammatory Th1 response. More importantly, we find the heightened Th1 response in BTK-deficient mice to result from both T cell-extrinsic and -intrinsic mechanisms. BTK-deficient dendritic cells secret elevated levels of the Th1-polarizing cytokine IL-12 and BTK-deficient T cells are inherently more prone to Th1 differentiation. Thus, BTK plays critical roles in maintaining gut immune homeostasis and preventing inflammation via regulating T-cell polarization.
... Both CD8 + and CD4 + T cells are IL-10 sources and a high proportion Accepted Article simultaneously produce IFNγ (157), likely supported by IL-27 production (158) and potentially in direct response to parasite shed trans-sialidase (123). B cells also produce IL-10 (135) and overall IL-10 production is lower in B1 B cell-deficient mice early during infection (159). CD11b+ B1 B cells from asymptomatic, infected individuals show increased capacity to produce IL-10 compared to those with cardiac disease symptoms (138). ...
Trypanosoma cruzi is a remarkably versatile parasite. It can parasitize almost any nucleated cell type and naturally infects hundreds of mammal species across much of the Americas. In humans it is the cause of Chagas disease, a set of mainly chronic conditions predominantly affecting the heart and gastrointestinal tract that can progress to become life threatening. Yet around two thirds of infected people are long‐term asymptomatic carriers. Clinical outcomes depend on many factors, but the central determinant is the nature of the host‐parasite interactions that play out over the years of chronic infection in diverse tissue environments. In this review, we aim to integrate recent developments in the understanding of the spatial and temporal dynamics of T. cruzi infections with established and emerging concepts in host immune responses in the corresponding phases and tissues.
... Knowledge of the immune response and cytokine production patterns in patients with Chagas disease is a cornerstone for identifying the clinical course, which can be unpredictable, and enables identification of cells and molecules that are associated with a better prognosis. The resistance or susceptibility to T. cruzi infection may depend on the cytokine profile, with Th1 cytokines (IFN-␥, tumor necrosis factor alpha [TNF-␣], and IL-12) promoting resistance (25)(26)(27)(28) and regulatory or Th2 cytokines (IL-10, IL-4, and transforming growth factor  [TGF-]) promoting susceptibility (29). ...
The major problem with Chagas disease is evolution of the chronic indeterminate form to a progressive cardiac disease. Treatment diminishes parasitemia but not clinical progression, and the immunological features involved are unclear. Here, we studied the clinical course and the immune response in patients with chronic-phase Chagas disease at 48 months after benznidazole treatment. Progression to the cardiac form of Chagas disease or its aggravation was associated with higher in vitro antigen-specific production of interferon γ (IFN-γ) in patients with cardiac Chagas disease than in patients with the indeterminate form. Predominance of IFN-γ over interleukin (IL)-10 production in antigen-specific cultures was associated with cardiac involvement. A significant increase in the number of antigen-specific T helper 1 cells (T-Bet ⁺ IFN-γ ⁺ ) and a significantly higher IFN-γ ⁺ /IL-10 ⁺ ratio were observed in patients with cardiac Chagas disease than in patients with the indeterminate form. Cardiac damage was associated with higher numbers of T helper cells than those of cytotoxic T lymphocytes producing IFN-γ. Patients with cardiac Chagas disease had predominant CD25 ⁻ and CD25 low T regulatory (Treg) subpopulations, whereas patients with the indeterminate form manifested a higher relative mean percentage of CD25 high Tregs. These findings suggest that at 48 months after benznidazole treatment, the disease can worsen or progress to the cardiac form. The progression may be related to increased IFN-γ production (mostly from CD4 ⁺ T cells) relative to IL-10 production and Treg percentage. Patients with the indeterminate form of Chagas disease show a more balanced ratio of pro- and anti-inflammatory cytokines.
... In contrast, treatment with compounds 1 and 2 elicited significantly higher IL-10. Various studies have reported that increased susceptibility of infected animals correlates with enhanced production of the anti-inflammatory cytokine IL-10 (Minoprio et al. 1993, Reed et al. 1994. Our results are consistent with previous works; they demonstrate that treatment with triterpenes suppresses the production of proinflammatory cytokines such as γ-IFN and generates IL-10 (Nataraju et al. 2009, Martín et al. 2010. ...
The protozoan Trypanosoma cruzi causes Chagas' disease, a neglected illness that remains a relevant public health concern in Latin America. In Brazil, Benznidazole is available for its treatment. This compound is effective against circulating forms of the parasite in the acute phase of the disease, but its efficacy during the chronic stage is debatable. The search for new medications that can treat Chagas' disease is therefore mandatory. Natural sources display a wide range of secondary metabolites and may play an important role in the discovery of new potential drugs. Miconia is one of the largest genus of the family Melastomataceae and includes approximately 1,000 plant species; Brazil alone is home to approximately 250 of these species, which exist in forests and savannas. Studies on the various biological activities of the Miconia species have reported promising results. Several researchers have screened these plants as well as their extracts in vitro against trypomastigote forms of T. cruzi, which displayed significant trypanocidal activity. It has been demonstrated that the presence of ursolic and oleanolic determines this biological activity.
... Interestingly, this was associated with a reduced parasitemia in acutely infected animals, sustaining the harmful role for polyclonal B stimulation in the control of the acute infection (Minoprio et al., 1991), though other mechanisms likely contribute to the improved control in Xid mice. Indeed, they are also relatively deficient in IL10 (CD5 1 B cells are important producers of IL10), which likely allows a better IFN-γ-dependent control of the infection (Minoprio et al., 1993). Moreover, the Bruton's tyrosine kinase (Btk), deficient in Xid mice, has been shown later on to also be expressed by other cells of the innate and adaptative immune system, which complicates the interpretation of the results (Brunner et al., 2005). ...
Control of T. cruzi infection requires the activation of multiple immune effector mechanisms in relation to the presence of both extracellular trypomastigotes and intracellular amastigotes. Protection is mainly governed by IFNs (initially type 1 IFNs, then IFN-?). However, it is worth noting that neutrophils and iNKT cells seem to have an important role in the very initial steps of the infection, without forgetting the essential contribution of NK cells and macrophages later on. The parasite has evolved an impressive number of mechanisms allowing it to establish slowly as well as to escape such complex immune response. Its ability is to temporarily limit Ag presentation through MHC class I molecules and to favor the release of amastigotes that invade preferentially unactivated macrophages in particular. Actually, the parasite is most generally on the winning side, as the host does not reach eliminating it. Thus, T. cruzi seems to be a real magician that adapts to many adverse situations. To date it is not known why the host does not reach eliminating the parasite and remains lifelong infected. Late chronic infection in humans is associated with the progressive disappearance of early-activated T cells and waning of T cell responses, atleast in the absence of reinfections. The underlying mechanisms should be addressed, keeping in mind that it remains to know if the host would actually benefit from a better efficient immune response in the long term, since it might have pathological consequences in some chronically infected individuals.
... Xid mice showed a natural resistance to this pathogen, possibly related to the absence of B-1 cells and a concomitant skewed natural IgG antibody repertoire (Santos-Lima et al. 2001). Furthermore, in xid mice, IL-10 production by B cells was greatly decreased, leading to increased IFNγ production by T helper-1 cells, which enhanced parasite clearance (Minoprio et al. 1993). Likewise, Leishmania major infection showed increased production of IFNγ and protection from severe disease in xid mice, but in WT mice, depletion of B-1 cells did not convey the same protection (Hoerauf et al. 1994;Babai et al. 1999). ...
Since the original identification of Bruton's tyrosine kinase (BTK) as the gene defective in the primary immunodeficiency X-linked agammaglobulinemia (XLA) in 1993, our knowledge on the physiological function of BTK has expanded impressively. In this review, we focus on the role of BTK during B cell differentiation in vivo, both in the regulation of expansion and in the developmental progression of pre-B cells in the bone marrow and as a crucial signal transducer of signals downstream of the IgM or IgG B cell antigen receptor (BCR) in mature B cells governing proliferation, survival, and differentiation. In particular, we highlight BTK function in B cells in the context of host defense and autoimmunity. Small-molecule inhibitors of BTK have very recently shown impressive anti-tumor activity in clinical studies in patients with various B cell malignancies. Since promising effects of BTK inhibition were also seen in experimental animal models for lupus and rheumatoid arthritis, BTK may be a good target for controlling autoreactive B cells in patients with systemic autoimmune disease.
... In contrast, treatment with compounds 1 and 2 elicited significantly higher IL-10. Various studies have reported that increased susceptibility of infected animals correlates with enhanced production of the anti-inflammatory cytokine IL-10 (Minoprio et al. 1993, Reed et al. 1994. Our results are consistent with previous works; they demonstrate that treatment with triterpenes suppresses the production of proinflammatory cytokines such as γ-IFN and generates IL-10 (Nataraju et al. 2009, Martín et al. 2010. ...
The protozoan Trypanosoma cruzi causes Chagas' disease, a neglected illness that remains a relevant public health concern in Latin America. In Brazil, Benznidazole is available for its treatment. This compound is effective against circulating forms of the parasite in the acute phase of the disease, but its efficacy during the chronic stage is debatable. The search for new medications that can treat Chagas' disease is therefore mandatory. Natural sources display a wide range of secondary metabolites and may play an important role in the discovery of new potential drugs. Miconia is one of the largest genus of the family Melastomataceae and includes approximately 1,000 plant species; Brazil alone is home to approximately 250 of these species, which exist in forests and savannas. Studies on the various biological activities of the Miconia species have reported promising results. Several researchers have screened these plants as well as their extracts in vitro against trypomastigote forms of T. cruzi, which displayed significant trypanocidal activity. It has been demonstrated that the presence of ursolic and oleanolic determines this biological activity.
... Xid immunodeficient mice influences resistance to infection. Surprisingly, T. cruzi infected Xid mice were more resistant than wild-type mice, and the resistance was associated with the absence of IL-10 secreting B1 cells and increased production of IFN- [63,64]. ...
Trypanosoma cruzi infection was studied in mouse lines selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory reaction and for high (HIII) or low (LIII) antibody (Ab) responses to complex antigens. Resistance was associated with gender (females) and strain-the high responder lines AIRmax and HIII were resistant. The higher resistance of HIII as compared to LIII mice extended to higher infective doses and was correlated with enhanced production of IFN-γ and nitric oxide production by peritoneal and lymph node cells, in HIII males and females. We also analyzed the involvement of previously mapped Ab and T. cruzi response QTL with the survival of Selection III mice to T. cruzi infections in a segregating backcross [F1(HIII×LIII) ×LIII] population. An Ab production QTL marker mapping to mouse chromosome 1 (34.8 cM) significantly cosegregated with survival after acute T. cruzi infections, indicating that this region also harbors genes whose alleles modulate resistance to acute T. cruzi infection.
... We observed that the response of these cells was also sensitive to the effect of the hydroalcoholic extract. The polyclonal B cell activation detected during T. cruzi infection seems to have pathological consequences for the host, since mice with a genetically determined defect in B cell response showed neither polyclonal B cell activation nor heart tissue pathology (38). Our findings that the hydroalcoholic extract could decrease immunoglobulin secretion by preactivated B cells obtained from T. cruzi-infected mice open the possibility for a therapeutic use of the extract from C. sympodialis in conditions associated with dysregulated B cell function or increased immunoglobulin secretion. ...
Cissampelos sympodialis Eichl species are used in folk medicine for the treatment of asthma, arthritis and rheumatism. In the present study, we investigated the immunomodulatory effect of an aqueous fraction of a 70% (v/v) ethanol extract of C. sympodialis leaves on B lymphocyte function. The hydroalcoholic extract inhibited the in vitro proliferative response of resting B cells induced by LPS (IC50 = 17.2 mug/ml), anti-delta-dextran (IC50 = 13.9 mug/ml) and anti-IgM (IC50 = 24.3 mug/ ml) but did not affect the anti-MHC class II antibody-stimulated proliferative response of B cell blasts obtained by stimulation with IL-4 and anti-IgM. Incubation with the hydroalcoholic extract used at 50 mug/ml induced a 700% increase in intracellular cAMP levels. IgM secretion by resting B cells (obtained from normal mice) and polyclonally activated B cells (obtained from Typanosoma cruzi-infected animals) was inhibited by the hydroalcoholic extract. The latter were more sensitive to the hydroalcoholic extract since 6.5 mug/ nil induced a 20% inhibition in the response of cells from normal mice while it inhibited the response of B cells from infected animals by 75%. The present data indicate that the alcoholic extract of C. sympodialis inhibited B cell function through an increase in intracellular cAMP levels. The finding that the hydroalcoholic extract inhibited immunoglobulin secretion suggests a therapeutic use for the extract from C. sympodialis in conditions associated with unregulated B cell function and enhanced immunoglobulin secretion. Finally, the inhibitory effect of the hydroalcoholic extract on B cells may indicate an anti-inflammatory effect of this extract.
... Interestingly, the crossing of BALB.Xid females with BALB/c males resulted in F1 male mice that phenocopy the BALB.Xid, whereas the F1 female were similar to BALB/c [31]. Further studies revealed that Xid mediated resistance to T. cruzi infection was IFN-c dependent [32]. In this context, although we detected no differences in production and responses to IFN-c between F1(AXB) x F1(BXA) (data not shown), further investigation will be required to address if the putative X-linked mutations carried by A/J mouse maps on the Xid locus. ...
The development of Chagas disease is determined by a complex interaction between the genetic traits of both the protozoan parasite, T. cruzi, and the infected host. This process is regulated by multiple genes that control different aspects of the host-parasite interaction. While determination of the relevant genes in humans is extremely difficult, it is feasible to use inbred mouse strains to determine the genes and loci responsible for host resistance to infection. In this study, we investigated the susceptibility of several inbred mouse strains to infection with the highly virulent Y strain of T. cruzi and found a considerable difference in susceptibility between A/J and C57BL/6 mice. We explored the differences between these two mouse strains and found that the A/J strain presented higher mortality, exacerbated and uncontrolled parasitemia and distinct histopathology in the target organs, which were associated with a higher parasite burden and more extensive tissue lesions. We then employed a genetic approach to assess the pattern of inheritance of the resistance phenotype in an F1 population and detected a strong parent-of-origin effect determining the susceptibility of the F1 male mice. This effect is unlikely to result from imprinted genes because the inheritance of this susceptibility was affected by the direction of the parental crossing. Collectively, our genetic approach of using the F1 population suggests that genes contained in the murine chromosome X contribute to the natural resistance against T. cruzi infection. Future linkage studies may reveal the locus and genes participating on the host resistance process reported herein.
... Activation of macrophages by parasite antigens results in proinflammatory cytokine production and consequent control of parasitemia and mortality [24]. On the other hand, it has been observed that this protein induces high production of IL-6 [13, 15], according to our results and because of the pleiotropic character of IL-6 has made it difficult to obtain a clear answer for the role of this cytokine in this model; however, the production of IL-6 observed in PBMCs could possibly modulate the differentiation of T cells infiltrated through the process of chemotaxis toward a Th2 pattern [37] and may later be involved in the maturation process of B cell [13], during polyclonal activation observed in the acute phase of infection [38]. This inflammatory T cell and antibody response leads to control—but not complete elimination—of tissue and blood parasitism. ...
The acute phase of Chagas' disease in mice and human is marked by states of immunosuppression, in which
Trypanosoma cruzi
replicates extensively and releases immunomodulatory molecules that delay parasite-specific responses mediated by effector T cells. This mechanism of evasion allows the parasite to spread in the host. Parasite molecules that regulate the host immune response during Chagas’ disease have not been fully identified, particularly proteins of the amastigote stage. In this work, we evaluated the role of the GPI anchored SSP4 protein of
T. cruzi
as an immunomodulatory molecule in peripheral blood mononuclear cells (PBMCs). rMBP::SSP4 protein was able to stimulate nitric oxide (NO) production. Likewise, rMBP::SSP4 induced the expression of genes and production of molecules involved in the inflammatory process, such as, cytokines, chemokines, and adhesion molecules (CAMs) as determined by RT-PCR and ELISA. These results suggest that the amastigote SSP4 molecule could play a key role in the immunoregulatory and/or immunosuppressive process observed in the acute phase of infection with
T. cruzi
.
... MZ: marginal zone B cells, GCs: germinal centers. IL-10-secreting B1 cells and high levels of IFN-gamma [28]. These results suggested that B1 cells play a pathological rather than protective role in Chagas' disease. ...
In this review, we discuss how protozoan parasites alter immature and mature B cell compartment. B1 and marginal zone (MZ) B cells, considered innate like B cells, are activated during protozoan parasite infections, and they generate short lived plasma cells providing a prompt antibody source. In addition, protozoan infections induce massive B cell response with polyclonal activation that leads to hypergammaglobulnemia with serum antibodies specific for the parasites and self and/or non related antigens. To protect themselves, the parasites have evolved unique ways to evade B cell immune responses inducing apoptosis of MZ and conventional mature B cells. As a consequence of the parasite induced-apoptosis, the early IgM response and an already establish humoral immunity are affected during the protozoan parasite infection. Moreover, some trypanosomatides trigger bone marrow immature B cell apoptosis, influencing the generation of new mature B cells. Simultaneously with their ability to release antibodies, B cells produce cytokines/quemokines that influence the characteristic of cellular immune response and consequently the progression of parasite infections.
... These results support the hypothesis that severity of the disease in chronic T. cruzi infection is tightly linked to the relative success in limiting parasite levels [14,34]. It has been shown in the murine model that a Th1 response is able to control T. cruzi infection and to reduce the severity of the disease [35][36][37][38][39][40]. Although inflammatory cytokines IL-6 and TNF-α were detected at 3 h and 12 h post-immunization in sera of mice immunized with adjuvant, rTcSSP4 protein, pBk-CMV, and pBCSSP4, INF-γ was detected only at 3 h post-immunization in sera of mice immunized with pBCSSP4. ...
Immunization of mice with plasmids containing genes of Trypanosoma cruzi induces protective immunity in the murine model of Chagas disease. A cDNA clone that codes for an amastigote-specific surface protein (TcSSP4) was used as a candidate to develop a DNA vaccine. Mice were immunized with the recombinant protein rTcSSP4 and with cDNA for TcSSP4, and challenged with bloodstream trypomastigotes. Immunization with rTcSSP4 protein makes mice more susceptible to trypomastigote infection, with high mortality rates, whereas mice immunized with a eukaryotic expression plasmid containing the TcSSP4 cDNA were able to control the acute phase of infection. Heart tissue of gene-vaccinated animals did not show myocarditis and tissue damage at 365 days following infection, as compared with control animals. INF-γ was detected in sera of DNA vaccinated mice shortly after immunization, suggesting the development of a Th1 response. The TcSSP4 gene is a promising candidate for the development of an anti-T. cruzi DNA vaccine.
... A predominant and persistent proinflammatory profile contributed to the higher mortality observed in Balb/Xid mice. These data are in contrast with those reported in studies using Balb/Xid mice in models of parasitemia, such as that caused by Trypanosoma cruzi (Minoprio et al. 1993) or Leishmania major (Hoerauf et al. 1994). In those models, the Balb/Xid mice presented more favorable clinical evolution than did other mice. ...
Sepsis syndrome is caused by inappropriate immune activation due to bacteria and bacterial components released during infection. This syndrome is the leading cause of death in intensive care units. Specialized B-lymphocytes located in the peritoneal and pleural cavities are known as B-1 cells. These cells produce IgM and IL-10, both of which are potent regulators of cell-mediated immunity. It has been suggested that B-1 cells modulate the systemic inflammatory response in sepsis. In this study, we conducted in vitro and in vivo experiments in order to investigate a putative role of B-1 cells in a murine model of LPS-induced sepsis. Macrophages and B-1 cells were studied in monocultures and in co-cultures. The B-1 cells produced the anti-inflammatory cytokine IL-10 in response to LPS. In the B-1 cell-macrophage co-cultures, production of proinflammatory mediators (TNF-α, IL-6 and nitrite) was lower than in the macrophage monocultures, whereas that of IL-10 was higher in the co-cultures. Co-culture of B-1 IL-10(-/-) cells and macrophages did not reduce the production of the proinflammatory mediators (TNF-α, IL-6 and nitrite). After LPS injection, the mortality rate was higher among Balb/Xid mice, which are B-1 cell deficient, than among wild-type mice (65.0% vs. 0.0%). The Balb/Xid mice also presented a proinflammatory profile of TNF-α, IL-6 and nitrite, as well as lower levels of IL-10. In the early phase of LPS stimulation, B-1 cells modulate the macrophage inflammatory response, and the main molecular pathway of that modulation is based on IL-10-mediated intracellular signaling.
... Nevertheless, experimental investigations question this simplistic interpretation and open the possibility that these cells might have a more complex participation in immunity. For instance, Minoprio et al. (1993) have shown that Xid mice, being animals deprived of B-1 cells, are more effective to cope with T. cruzi infection than with wild type controls. Moreover, Popi et al. (2008) clearly demonstrated that Xid mice, when infected intra-tracheally with P. brasiliensis, have a longer survival than wild type counterparts. ...
Characterization of the origin, properties, functions and fate of cells is a fundamental task for the understanding of physiological and pathological phenomena. Despite the bulk of knowledge concerning the diverse characteristics of mammalian cells, some of them, such as B-1 cells, are still poorly understood. Here we report the results obtained in our laboratory on these cells in the last 10 years. After showing that B-1 cells could be cultured and amplified in vitro, a series of experiments were performed with these cells. They showed that B1 cells reside mostly in the peritoneal and pleural cavities, migrate to distant inflammatory foci, coalesce to form giant cells and participate in granuloma formation, both in vitro and in vivo. They are also able to present antigens to immunologically responsive cells and are endowed with regulatory properties. Further, we have also shown that these cells facilitate different types of infection as well as tumor growth and spreading. These data are presently reviewed pointing to a pivotal role that these cells may play in innate and acquired immunity.
... After control of the acute phase in immunocompetent mice, the infection turns into a chronic phase (starting around day 21 postinfection [p.i.]) where parasites are no longer detectable by light microscopy in the bloodstream but form inflammatory nests in various tissues, a process associated with chagasic pathology, in which antiparasite cytotoxic T lymphocytes or autoimmune mechanisms may play a role (14,21,29). ...
Trypanosoma cruzi, the causative agent of Chagas' disease, is known to be susceptible to nitric oxide (NO)-dependent killing by gamma interferon-activated
macrophages. Mice deficient for inducible nitric oxide synthase (iNOS) are highly susceptible toT. cruzi, and inhibition of iNOS from the beginning of infection was reported to lead to an increase in trypomastigotes in the blood
and to high mortality. In the present study, we investigated whether NO production is essential for the control of T. cruzi in all phases of the infection. BALB/c mice were treated at different time intervals after T. cruzi infection with an iNOS inhibitor, aminoguanidine orl-N6-(1-iminoethyl)-lysine (L-NIL). Treatment initiated with the beginning of the infection resulted in 100% mortality by day
16 postinfection (p.i.). If treatment was started later during the acute phase at the peak of parasitemia (day 20 p.i.), all
the mice survived. Parasitemia was cleared and tissue amastigotes became undetectable in these mice even in the presence of
the iNOS inhibitor L-NIL. Inhibition of iNOS in the chronic phase of the infection, i.e., from day 60 to day 120 p.i., with
L-NIL did not result in a reappearance of parasitemia. These data suggest that while NO is essential for T. cruzi control in the early phase of acute infection, it is dispensable in the late acute and chronic phase, revealing a fundamental
difference in control mechanisms compared to those in infections by other members of the orderKinetoplastida, e.g., Leishmania major.
The role of gamma delta T cells in the immunopathology of Chagas' disease is evaluated by monitoring the course of Trypanosoma cruzi infection in mice lacking gamma delta T cells after disruption of the T-cell receptor C delta locus. Levels of parasitemia, states of lymphocyte activation, and levels of lymphokine production as well as tissue pathology are compared in delta knockout mice and their littermates in acute and chronic phases of infection. Although the levels of circulating parasites do not significantly differ in the two groups, mortality scores and numbers of inflammatory lesions of skeletal and cardiac muscles are lower in gamma delta T cell-deficient m ice than in littermate controls. Furthermore, polyclonal lymphocyte activation, as measured by proliferative activities and numbers of B- and T-cell blasts in the spleen, are reduced in deficient mice in the acute and chronic phases of infection. Levels of gamma interferon mRNA obtained from total spleen cells, known to be a critical lymphokine in resistance to T. cruzi infection, are significantly higher in uninfected gamma delta T cell-deficient mice than in control animals and slightly above levels for littermates in the course of acute infection. Interestingly, however, in chronic phases, the levels of this lymphokine are not statistically different between the two groups of mice. These results indicate that gamma delta T cells do not play a crucial role in parasite clearance during the acute phase of the disease but contribute to the mechanisms leading to tissue damage and pathology.
Chagas disease is a complex disorder in which the immunological response developed by the host plays a fundamental role, not only in the clearance of the parasite but also in the inflammatory status observed in specific affected tissues. Chagas disease has two phases, acute and chronic, the latter being established in those cases where treatment with currently available anti-parasitic drugs (nifurtimox and benznidazole) is either not applied or not effective. During the chronic phase, the disease may remain without any detectable symptoms for several decades or progress toward cardiac, digestive, neurological forms, or even a combination of these alterations. The immune response developed in all of these conditions is flowery and comprises humoral and cellular components; however the clearance of the parasite is incomplete due to the multiple mechanisms that T. cruzi deploys in order to perpetuate itself within the host.
Trypanosoma cruzi interacts with the different arms of the innate and adaptive host's immune response in a very complex and flowery manner. The history of host-parasite co-evolution has provided this protozoan with means of resisting, escaping or subverting the mechanisms of immunity and establishing a chronic infection. Despite many decades of research on the subject, the infection remains incurable, and the factors that steer chronic Chagas disease from an asymptomatic state to clinical onset are still unclear. As the relationship between T. cruzi and the host immune system is intricate, so is the amount and diversity of scientific knowledge on the matter. Many of the mechanisms of immunity are fairly well understood, but unveiling the factors that lead each of these to success or failure, within the coordinated response as a whole, requires further research. The intention behind this Review is to compile the available information on the different aspects of the immune response, with an emphasis on those phenomena that have been studied and confirmed in the human host. For ease of comprehension, it has been subdivided in sections that cover the main humoral and cell-mediated components involved therein. However, we also intend to underline that these elements are not independent, but function intimately and concertedly. Here, we summarize years of investigation carried out to unravel the puzzling interplay between the host and the parasite.
B cells are notorious actors for the host's protection against several infectious diseases. So much so that early vaccinology seated its principles upon their long-term protective antibody secretion capabilities. Indeed, there are many examples of acute infectious diseases that are combated by functional humoral responses. However, some chronic infectious diseases actively induce immune deregulations that often lead to defective, if not deleterious, humoral immune responses. In this review we summarize how Leishmania and Trypanosoma spp. directly manipulate B cell responses to induce polyclonal B cell activation, hypergammaglobulinemia, low-specificity antibodies, limited B cell survival, and regulatory B cells, contributing therefore to immunopathology and the establishment of persistent infections.
B-1 cells are a subtype of B cells with peculiar characteristics. These cells are distinct from B-2 lymphocytes in their morphology, ontogeny, tissue distribution and phenotypic functional features. B-1 cells can participate in the immune response in several ways, for example, by being recruited to inflammatory foci, producing large amounts of IL-10 cytokine, and differentiating into IgM-secreting cells or phagocytes. Nevertheless, the role of B-1 cells in the pathogenesis of experimental leishmaniasis has not been fully elucidated. Here, we evaluated the role of B-1 cells in Leishmania (L.) amazonensis infection using X-linked immunodeficient mice that possess a mutation in Bruton's tyrosine kinase (Btk) that leads to a reduced number of B-1 cells. The course of infection and the corresponding immune response were analyzed in infected mice. XID mice showed an increase in parasite number in paws, lymph nodes and spleen compared to BALB/c infected controls. Infected XID mice had higher IL-10 levels and lower anti-Leishmania IgM. The adoptive transfer of peritoneal B-1 cells into XID mice restored peritoneal B-1 cells and parasite burden in the footpad in a pattern similar to that observed in the BALB/c controls at 10 weeks. Our results demonstrate the higher susceptibility of XID mice to infection with L. (L.) amazonensis compared to controls. In addition, we show that the presence of B-1 cells contributes to improved animal resistance to parasites, suggesting that these cells are involved in the control of cutaneous infection caused by L. (L.) amazonensis.
This chapter presents in chronological order the principal data obtained in experimental infections with Trypanosoma cruzi in different animal species used in the study of the natural history of Chagas disease. Presented are the results obtained in mice, rats, dogs, rabbits, guinea, pigs, hamsters, and monkeys (autochthonous and nonautochthonous from American Continent) regarding the reproducibility of the acute and chronic phases of the infection and clinical manifestations of each phase and clinical form of the disease when successfully developed. Parasitological, serological, immunological, histopathological and clinical features are described. The principal advantages and disadvantages of each model are mentioned.
The mortality of patients who suffer from systemic infections is dependent on exogenous and endogenous factors. Exogenous factors include the type of microbial pathogen, the expression of virulence factors and appropriateness of medical therapy, whereas age, nutritional status, and immune deficiency are endogenous factors. It is well known that the mortality of bacterial infection markedly differs amongst genetically distinct inbred mouse strains and it has been suggested that the genetic background may also be a determinant of outcome from septic shock. Indeed, at least one study has investigated polymorphisms within the tumor necrosis factor (TNF) locus in relation to mortality from sepsis. For several reasons such studies are difficult to interpret. First, the cause of mortality in sepsis is not known, and indeed may differ among patients. From a genomics point of view it would be most important to be able to distinguish between patients that die because of overwhelming (bacterial) infection, versus those that succumb due to hypotension and ischemia/reperfusion damage, because these respective processes are controlled by different genes. Secondly, studies on disease genomics are critically dependent on the availability of an appropriate control population, or family members that express the disease. Because of the heterogeneous nature of sepsis, its occurrence at the extremes of age, the absence of families with sepsis syndrome, and the importance of underlying diseases, at present any search for the genomics of the sepsis syndrome is cumbersome and in most cases futile.
The Epstein-Barr virus-induced gene 3 (EBI3) is a member of the interleukin (IL)-12-family structurally related to the subunit p40 of IL-12 and forms a heterodimer either with the p28 subunit to build IL-27 or with p35 to form IL-35. IL-27 is secreted by antigen presenting cells whereas IL-35 appears to be produced mainly by regulatory T cells and regulatory B cells but both cytokines negatively regulate inflammatory immune responses. We here analyzed the function of EBI3 during infection with the intracellular parasite Trypanosoma cruzi. Compared to C57BL/6 wildtype mice, EBI3-deficient ((-/-) ) mice showed a higher parasitemia associated with an increased mortality rate. EBI3(-/-) mice displayed an elevated inflammatory immune response with an increased production of T helper (Th) type 1-, Th type 2- and Th type 17-derived cytokines. The increased Th2 immune response appears to have overridden the otherwise protective Th1 and Th17 immune responses by the induction of arginase-1-expressing alternatively activated macrophages in these mice. Hence, neutralization of IL-4 and arginase-1 activity partially restored protective immune responses in EBI3(-/-) mice. So far, our results demonstrate that EBI3 is an essential general regulator of inflammatory immune response in experimental Chagas disease and is required for control of T. cruzi infection by inhibiting Th2-dependent alternative macrophage activation. Further studies have to dissect the underlying mechanisms and clarify whether EBI3 associated with IL-27 or/and IL-35 account for its anti-inflammatory character in the parasitic disease. This article is protected by copyright. All rights reserved.
This chapter presents the data generated by the experimental infection of dogs, monkeys, and laboratory rodents, and gathers the scarce information of T. cruzi natural and experimental infections in livestock. It also focuses on the specific natural way of infection of these animals and the potential and possible risks, as well as the history of the infection spreading from these animals to other animals, including humans. This is partly speculative due to the very poor information available on the real status and role of livestock in the epidemiology of the infection. Trypanosoma cruzi is a human parasite but is also found in many other animal species, both wild and domestic; human infection can occur in rural as well as in urban areas, which reveals various roles of insects and other mammals in its epidemiology. T. cruzi can be naturally found in dogs, cats, cattle, goats, sheep, rabbits, and equines. From a veterinary point of view, it is difficult to classify these various categories of animals since their role is variable from one situation to another.
Since more than 30 years, the hypothesis of autoimmunity is considered for chronic Chagas disease, especially for the most severe manifestation: the chronic Chagas heart disease. Actually, many studies were performed to sustain this hypothesis and successful outcomes reached to demonstrate molecular mimicry and presence of autoreactive T and B cells with potential pathological impact. The most severe pathology induced by Trypanosoma cruzi concerns the heart disease that affects 20–30% of the infected patients and leads to sudden death. Only 5–10% suffer from megaesophagus, megacolon, or peripheral neuropathies. The pathophysiology of Chagas heart disease is still not totally understood and two main mechanisms have been proposed; one is parasite-dependent myocardial damage and the other is impaired immunological responses associated to molecular mimicry. If the clinical features were well known since the beginning of the twentieth century, it remains to explore the mechanisms underlying the development of this chronic disease. Moreover, the recent researches have mostly focused on mechanisms of protection mediated by CD8+ T cells and definition of candidates for vaccination. Due to the restrictive rules of ethical approaches in humans, this chapter discusses the validity of the mouse model to learn about the pathological consequences of host-immune response to T. cruzi.
The immune response to leishmaniasis is complex, and the result of infection depends on both the genetic composition of the
Leishmania
species and the immunity of the host. Clinical and experimental evidence suggest that the activation of B cells leads to exacerbation of visceral leishmaniasis. However, the role of B-1 cells (a subtype of B lymphocytes) in the pathogenesis of experimental visceral leishmaniasis has not yet been elucidated. In this study, we investigated the importance of B-1 cells in experimental infection with
Leishmania.
(
L.
)
chagasi
. Our results showed that BALB/XID mice (X-linked immunodeficient mice which are genetically deficient in B-1 cells) infected with
L.
(
L.
)
chagasi
for 45 days had a significant reduction in parasite load in the spleen when compared with control mice. Cytokine analysis showed that the BALB/XID mice had lower amounts of IL-10 in their sera compared with control group. In addition, the transfer of B-1 cells from wild type mice into IL-10KO animals led to an increase in susceptibility to
L.
(
L.
)
chagasi
infection in the IL-10KO mice, suggesting that the IL-10 produced by these cells is important in experimental infection. Our results suggest that B-1 cells may play an important role in susceptibility to
L.
(
L.
)
chagasi
.
Chronic obstructive pulmonary disease (COPD) is characterized by a progressive decline in lung function, caused by exposure to exogenous particles, mainly cigarette smoke (CS). COPD is initiated and perpetuated by an abnormal CS-induced inflammatory response of the lungs, involving both innate and adaptive immunity. Specifically, B cells organized in iBALT structures and macrophages accumulate in the lungs and contribute to CS-induced emphysema, but the mechanisms thereof remain unclear. Here, we demonstrate that B cell-deficient mice are significantly protected against CS-induced emphysema. Chronic CS exposure led to an increased size and number of iBALT structures, and increased lung compliance and mean linear chord length in WT, but not B cell-deficient mice. The increased accumulation of lung resident macrophages around iBALT and in emphysematous alveolar areas in CS-exposed WT mice coincided with upregulated MMP12 expression. In vitro co-culture experiments using B cells and macrophages demonstrated that B cell-derived IL-10 drives macrophage activation and MMP12 upregulation, which could be inhibited by an anti-IL10 antibody. In summary, B cell function in iBALT formation seems necessary for macrophage activation and tissue destruction in CS-induced emphysema, and possibly provides a new target for therapeutic intervention in COPD.
La trypanosomose américaine ou maladie de Chagas se distingue de la trypanosomose africaine (ou maladie du sommeil) par le parasite, le vecteur et les symptômes cliniques. Cette infection parasitaire est localisée au continent américain et plus particulièrement à l'Amérique latine. La maladie de Chagas n'est plus considérée aujourd'hui comme un problème de santé publique grâce aux efforts conjugués pour le contrôle des vecteurs au niveau régional et des banques de sang. Il ne faut cependant pas sous-estimer la difficulté du maintien des campagnes de contrôle, l'existence de cycles sylvestres échappant à l'action des insecticides, et le contact des animaux réservoirs avec l'hôte.
We have followed CD4 and CD8 TCR V(beta) repertoires during the acute phase of Trypanosoma cruzi infection in a resistant mouse strain (C57BL/6). No major changes were found in the V(beta) TCR distributions analyzed (covering roughly 40% of the TCR repertoire) in peripheral CD4 T lymphocytes, confirming the polyclonal nature of CD4 T cell responses. In contrast, in most animals, an over-representation of V(beta)5 and V(beta)14 TCR families was disclosed in the CD8 T cell compartment, superimposed on a predominantly polyclonal response. The preferential expansion of V(beta)5+CD8+ T cells was also observed after infection of sensitive (C3H/HeJ, BALB/c) mouse strains. These observations suggest the existence of CD8 T cell-directed superantigenic activities associated with parasites.
Reduction in the parasitemic levels of the Y strain of Trypanosoma cruzi in mice treated with oral or intraperitoneal ursolic (UA) and oleanolic (OA) acids was evaluated during the acute phase of Chagas' disease. Oral administration of UA and OA (50 mg/Kg/day) provided the most significant reduction in the parasitemic peak, while intraperitoneal administration of UA and OA did not significantly affect the biological activity of the Y strain of T. cruzi. Interleukin levels in mice treated by the intraperitoneal route were compared to untreated chagasic mice. Reduced γ-IFN levels and enhanced IL-10 concentrations potentially explain the exacerbated parasitemia. Our data suggests an immunosuppressive effect for UA and OA, which could interfere with host control of parasitemia. Optimal results were achieved with oral administration. This observation may be explained by the low intestinal absorption of UA and OA, could cause a reduced immune response and promote parasite control. Taken together, these data demonstrate that triterpenes could be interesting compounds to develop therapeutically for the treatment of Chagas' disease.
Inflammation is powerful response in order to destroy invading organisms and an exaggerated response can lead to death of the host. Macrophages secrete mediators that activated circulating neutrophils leading to its migration into infectious site. Recently has been showing that lymphocytes have an action modulating the early phase of inflammatory response. In this article we will analyze the role of B1 in the inflammatory response of different origins and finally focus attention on sepsis. B lymphocyte deficiency has been linked to acute infection presumably owing to the lack of an adaptative immune response to effectively clear pathogens. Individuals with X-linked agammaglobulinemia (XLA) present B-1 lymphocyte deficiency caused by mutations in the Bruton's tyrosine kinase (Btk). Some data show that B-1 cells might contribute to susceptibility in experimental paracoccidioidomycosis. On the other hand, B-1 cells are shown to be detrimental in other mouse models of microbial infection, such as experimental Chagas' disease, leishmaniasis and Staphylococcus aureus-induced arthritis. B-1 cell plays a protective role in the host of the effects of endotoxemia. In a murine model of endotoxemia by LPS, B-1 cell participates in both IL-10 and IgM secretion with a consequent reduction in mortality.
The Xid mutation predominantly affects the development of B cells and consequently the levels and composition of natural antibodies in sera. In contrast to the congenic and susceptible BALB/c strain, immunodeficient BALB.Xid mice display a resistant phenotype both to acute Trypanosoma cruzi infection and to the development of severe cardiopathy. Because natural antibodies are known to be basically self-antigen driven, IgM and IgG natural antibody repertoires (NAR) were compared before and during infection in these two strains. The analysis revealed fundamental alterations of IgM and IgG NAR in pre- and post-infected Xid mice. In particular, relatively increased natural (pre-existing) autoreactive IgG, dominated by the unique recognition of a single band in autologous heart extracts, was typical for uninfected Xid mice. This natural autoreactive IgG directed to heart antigens disappeared early after infection not only in Xid, but also in individual BALB/c mice that survived the acute infection. Conversely, the subgroup of BALB/c mice that died early after infection presented the most pronounced instances of the rapid, relative increase of IgM reactivies to self and non-self proteins. These results suggest that self-reactive NAR may play a role in an immunoregulatory mechanism relevant for the determination of susceptibility/resistance to infections. This may act either by influencing specific responses, or by modulating the self-aggressive components responsible for pathology.
Host immunity affects tumor metastasis but the corresponding cellular and molecular mechanisms are not entirely clear. Here, we show that a subset of B lymphocytes (termed B-1 population), but not other lymphocytes, has prometastatic effects on melanoma cells in vivo through a direct heterotypic cell-cell interaction. In the classic B16 mouse melanoma model, one mechanism underlying this phenomenon is a specific up-regulation and subsequent homophilic interaction mediated by the cell surface glycoprotein MUC18 (also known as melanoma cell adhesion molecule). Presence of B-1 lymphocytes in a panel of tumor samples from melanoma patients directly correlates with MUC18 expression in melanoma cells, indicating that the same protein interaction exists in humans. These results suggest a new but as yet unrecognized functional role for host B-1 lymphocytes in tumor metastasis and establish a biochemical basis for such observations. Our findings support the counterintuitive central hypothesis in which a primitive layer of the immune system actually contributes to tumor progression and metastasis in a mouse model and in melanoma patients. Given that monoclonal antibodies against MUC18 are in preclinical development but the reason for their antitumor activity is not well understood, these translational results are relevant in the setting of human melanoma and perhaps of other cancers.
Cytolethal distending toxin (CDT) is a DNA-targeting agent produced by certain pathogenic gram-negative bacteria such as the periodontopathogenic organism Aggregatibacter actinomycetemcomitans. CDT targets lymphocytes and other cells causing cell cycle arrest and apoptosis, impairing the host immune response and contributing to the persistence of infections caused by this microorganism. In this study we explored the effects of CDT on the innate immune response, by investigating how it affects production of nitric oxide (NO) by macrophages.
Murine peritoneal macrophages were stimulated with Escherichia coli sonicates and NO production was measured in the presence or not of active CDT.
We observed that CDT promptly and significantly inhibited NO production by inducible nitric oxide synthase (iNOS) in a dose-dependent manner. This inhibition is directed towards interferon-gamma-dependent pathways and is not mediated by either interleukin-4 or interleukin-10.
This mechanism may constitute an important aspect of the immunosuppression mediated by CDT and may have potential clinical implications in A. actinomycetemcomitans infections.
The specificity and function of T helper (Th) immune responses underlying the induction, progression, and resolution of experimental autoimmune myocarditis (EAM) in A/J mice are unclear. Published data suggest involvement of both Th1 and Th2 responses in EAM; however, the previous inability to assess antigen-specific in vivo and in vitro T-cell responses in cardiac myosin-immunized animals has confounded our understanding of this important model of autoimmune myocarditis. The goal of our study was to develop an alternative model of EAM based on a recombinant fragment of cardiac myosin, in hopes that the recombinant protein will permit measurement of functional T-cell responses that is not possible with purified native protein. A/J mice immunized with a recombinant fragment of cardiac myosin spanning amino acids 1074-1646, termed Myo4, developed severe myocarditis characterized by cardiac hypertrophy, massive mononuclear cell infiltration and fibrosis, three weeks post-immunization. The mice also developed an IgG1 dominant humoral immune response specific for both Myo4 and purified cardiac myosin. The in vitro stimulation of splenocytes harvested from Myo4-immunized animals with Myo4 resulted in cellular proliferation with preferential production of the Th1- and Th17-associated cytokines, IFN-gamma, IL-17, and IL-6, respectively. Production of IL-4 was negligible by comparison. This study describes a new model of EAM, inducible by immunization with a specific fragment of cardiac myosin, from which antigen-specific analyses reveal an importance for both Th1 and Th17 immunity.
Resistance to Mycobacterium avium depends on both genetically encoded macrophage functions and acquired T-cell immunity. Cytokines may play a role in either type of resistance. We studied the expression of interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma) in naturally susceptible BALB/c (Bcgs) and naturally resistant C.D2 (Bcgr) congenic mice infected with two strains of M. avium (one highly virulent and another of low virulence). We observed that cytokine expression patterns correlated better with the virulence of the micro-organism than with the genetic background of the host. The control of the infection by the low virulence strain in either mouse strain was associated with an increased expression of IFN-gamma and IL-2. Only Bcgs mice infected with a virulent strain of M. avium were unable to restrict bacterial growth. An increased expression of IL-4, early during infection, was detected in the course of the latter infection but played no role in determining the susceptibility to infection. Neutralization of IFN-gamma or IL-2 with specific monoclonal antibodies led to an exacerbation of the infection in Bcgr mice by the two strains of M. avium and in Bcgs mice infected with the low virulence strain of M. avium.
(NZB x NZW)F1 (B/W) mice spontaneously develop a lupus-like syndrome characterized by an increased level of autoantibodies in old mice. We analysed the role of T cells in the regulation of anti-DNA antibody production by B cells in vitro as a function of age. In cultures of old mouse T and B cells, IgG and IgM anti-DNA antibodies were synthesized at high levels, in contrast to consistently lower amounts, particularly of IgG, measured in cultures of young mouse cells. Addition of young mouse T cells to old B cells inhibited IgG, but not IgM, anti-DNA production, whereas T cells from old mice stimulated IgG synthesis by young mouse B cells. Addition of supernatants harvested from concanavalin A (Con A)-stimulated T cells to B-cell cultures induced similar effects. Therefore, we evaluated possible modifications of lymphokine synthesis compared to that of the healthy NZW parent. T cells from old mice were able to secrete normal levels of interferon-gamma (IFN-gamma) and interleukin (IL)-10; however, secretion of IL-2 and IL-4 was dramatically decreased. Semi-quantitative polymerase chain reaction analysis of constitutive RNA messengers showed increased IFN-gamma levels in young and old B/W mice, and normal IL-10 mRNA levels in young and higher levels in old mice. Constitutive IL-2 and IL-4 mRNA were detected only after Con A stimulation and their levels decreased in old compared to young B/W mice; in particular IL-2 mRNA was considerably lower in old B/W than in control NZW mice. Taken together, these results suggest that, despite constitutive T-cell abnormalities, young B/W mice are able partially to control their lymphokine production, whereas aged mice exhibit a deficient synthesis, associated with an increased capacity to produce IFN-gamma.
In the present study we demonstrate that human monocytes activated by lipopolysaccharides (LPS) were able to produce high levels of interleukin 10 (IL-10), previously designated cytokine synthesis inhibitory factor (CSIF), in a dose dependent fashion. IL-10 was detectable 7 h after activation of the monocytes and maximal levels of IL-10 production were observed after 24-48 h. These kinetics indicated that the production of IL-10 by human monocytes was relatively late as compared to the production of IL-1α, IL-1β, IL-6, IL-8, tumor necrosis factor Oi(TNFα), and granulocyte colony-stimulating factor (G-CSF), which were all secreted at high levels 4-8 h after activation. The production of IL-10 by LPS activated monocytes was, similar to that of IL-1α, IL-1β, IL-6, IL-8, TNFα, granulocyte-macrophage colony-stimulating factor (GM-CSF), and G-CSF, inhibited by IL-4. Furthermore we demonstrate here that IL-10, added to monocytes, activated by interferon γ(IFN-γ), LPS, or combinations of LPS and IFN-γ at the onset of the cultures, strongly inhibited the production of IL-1α, IL-1β, IL-6, IL-8, TNFα, GM-CSF, and G-CSF at the transcriptional level. Viral-IL-10, which has similar biological activities on human cells, also inhibited the production of TNFα and GM-CSF by monocytes following LPS activation. Activation of monocytes by LPS in the presence of neutralizing anti-IL-10 monoclonal antibodies resulted in the production of higher amounts of cytokines relative to LPS treatment alone, indicating that endogenously produced IL-10 inhibited the production of IL-1α, IL-1β, IL-6, IL-8, TNFα, GM-CSF, and G-CSF. In addition, IL-10 had autoregulatory effects since it strongly inhibited IL-10 mRNA synthesis in LPS activated monocytes. Furthermore, endogenously produced IL-10 was found to be responsible for the reduction in class II major histocompatibility complex (MHC) expression following activation of monocytes with LPS. Taken together our results indicate that IL-10 has important regulatory effects on immunological and inflammatory responses because of its capacity to downregulate class II MHC expression and to inhibit the production of proinflammatory cytokines by monocytes.
For an exploration of the effects of interferon-inducible resistance mechanisms in acute American trypanosomiasis, the synthetic interferon inducer tilerone hydrochloride was administered to mice of the C57BL/6J strain, which is highly resistant to Trypanosoma cruzi, 18 to 24 h before infection with a potentially lethal dose of bloodstream trypomastigotes. Although all of the control mice died within 30 days of the acute infection, approximately 50% of the tilerone-treated animals were able to survive indefinitely (P less than 0.05). The tilerone-treated mice demonstrated significant levels of serum interferon and splenic natural killer cells at the time of infection. Macrophages isolated from the peritoneal cavities of tilerone-treated C57BL/6J mice appeared to kill significant numbers of trypanosomes during 2 to 3 days of in vitro culture, indicating that activated macrophages may contribute to the enhanced resistance to T. cruzi infection in these mice. Beige mice treated with tilerone did not survive T. cruzi infection as well as tilerone-treated heterozygotes did, suggesting a role for natural killer cells in interferon-induced resistance. These results suggest that interferon or effector mechanisms enhanced by interferon induction can play a significant role in influencing resistance to T. cruzi infection.
Ly-1 B cells have the distinctive property of continuous self-replenishment and, as we have shown previously, can be further distinguished from conventional B cells on the basis of greatly elevated constitutive and inducible production of the recently described cytokine interleukin 10 (IL-10). To test the possibility that IL-10 acts as either an autocrine or paracrine growth factor for Ly-1 B cells, we treated mice continuously from birth to 8 wk of age with a monoclonal rat IgM antibody that specifically neutralizes mouse IL-10. Mice treated in this way lacked peritoneal-resident Ly-1 B cells, contained greatly reduced serum immunoglobulin M levels, and were unable to generate significant in vivo antibody responses to intraperitoneal injections of alpha 1,3-dextran or phosphorylcholine, antigens for which specific B cells reside in the Ly-1 B cell subset. In contrast, conventional splenic B cells of anti-IL-10-treated mice were normal with respect to total numbers, phenotype, and in vitro responsiveness to B cell mitogens and the thymus-dependent antigen trinitrophenyl-keyhole limpet hemocyanin (TNP-KLH). The mechanism of Ly-1 B cell depletion appeared to be related to elevation of endogenous interferon gamma (IFN-gamma) levels in anti-IL-10-treated mice, since coadministration of neutralizing anti-IFN-gamma antibodies substantially restored the number of peritoneal-resident Ly-1 B cells in these mice. These results implicate IL-10 as a regulator of Ly-1 B cell development, and identify a procedure to specifically deplete Ly-1 B cells, thereby allowing further evaluation of the role of these cells in the immune system.
The contribution of autoimmunity in the genesis of chronic Chagas' heart pathology is not clear. In the present study, we show that: (a) BALB/c mice chronically infected with Trypanosoma cruzi reject syngeneic newborn hearts; (b) in vivo treatment with anti-CD4 but not anti-CD8 monoclonal antibodies (mAbs) abrogates rejection; (c) CD4+ T cells from chronically infected mice proliferate in vitro to syngeneic myocardium antigens and induce heart graft destruction when injected in situ; (d) anti-CD4 treatment of chronically infected mice establishes long-term tolerance to syngeneic heart grafts; and (e) the state of tolerance is related to in vitro and in vivo unresponsiveness of the CD4+ T cells. These findings allow us to suggest that autoimmunity is the major mechanism implicated in the rejection of syngeneic heart tissues grafted into the pinna of the ear of mice chronically infected with T. cruzi. The similarity of the lesions to those found in humans suggests that autoimmunity is involved in the pathogenesis of chagasic cardiomyopathy in humans. Moreover, this could imply therapeutic strategies by reestablishing long-term tissue-specific tolerance with anti-CD4 mAb treatment, mediating anergy, or deleting the responder CD4+ T cells to heart tissue antigens.
Studies were undertaken to determine whether interleukin 10, (IL-10) a cytokine shown to inhibit interferon gamma (IFN-gamma) production, was involved in Trypanosoma cruzi infections in mice. Exogenous IFN-gamma protects mice from fatal infection with T. cruzi. Furthermore, resistant B6D2 mice developed fatal T. cruzi infections when treated with neutralizing anti-IFN-gamma monoclonal antibody (mAb). Thus, endogenous as well as exogenous IFN-gamma is important in mediating resistance to this parasite. Because both T. cruzi-susceptible (B6) and -resistant (B6D2) mouse strains produced IFN-gamma during acute infection, we looked for the concomitant production of mediators that could interfere with IFN-gamma-mediated resistance to T. cruzi. We found that IL-10-specific mRNA was produced in the spleens of mice with acute T. cruzi infections. In addition, spleen cell culture supernatants from infected B6 mice, and to a lesser extent B6D2 mice, elaborated an inhibitor(s) of IFN-gamma production. This inhibitor(s) was neutralized by anti-IL-10 mAb. These experiments demonstrated the production of biologically active IL-10 during T. cruzi infection. In further studies in vitro, it was shown that IL-10 blocked the ability of IFN-gamma to inhibit the intracellular replication of T. cruzi in mouse peritoneal macrophages. Thus, in addition to its known ability to inhibit the production of IFN-gamma, IL-10 (cytokine synthesis inhibitory factor), may also inhibit the effects of IFN-gamma. These experiments demonstrate that IL-10 is produced during infection with a protozoan parasite and suggest a regulatory role for this cytokine in the mediation of susceptibility to acute disease.
Recombinant mouse interleukin 10 (IL-10) was exceedingly potent at suppressing the ability of mouse peritoneal macrophages (m phi) to release tumor necrosis factor alpha (TNF-alpha). The IC50 of IL-10 for the suppression of TNF-alpha release induced by 0.5 microgram/ml lipopolysaccharide was 0.04 +/- 0.03 U/ml, with as little as 1 U/ml suppressing TNF-alpha production by a factor of 21.4 +/- 2.5. At 10 U/ml, IL-10 markedly suppressed m phi release of reactive oxygen intermediates (ROI) (IC50 3.7 +/- 1.8 U/ml), but only weakly inhibited m phi release of reactive nitrogen intermediates (RNI). Since TNF-alpha is a T cell growth and differentiation factor, whereas ROI and RNI are known to inhibit lymphocyte function, it is possible that m phi exposed to low concentrations of IL-10 suppress lymphocytes. m phi deactivated by higher concentrations of IL-10 might be permissive for the growth of microbial pathogens and tumor cells, as TNF-alpha, ROI, and RNI are major antimicrobial and tumoricidal products of m phi. IL-10's effects on m phi overlap with but are distinct from the effects of the two previously described cytokines that suppress the function of mouse m phi, transforming growth factor beta and macrophage deactivation factor. Based on results with neutralizing antibodies, all three m phi suppressor factors appear to act independently.
A cytokine synthesis inhibitory factor (CSIF) is secreted by Th2 clones in response to Con A or antigen stimulation, but is absent in supernatants from Con A-induced Th1 clones. CSIF can inhibit the production of IL-2, IL-3, lymphotoxin (LT)/TNF, IFN-gamma, and granulocyte-macrophage CSF (GM-CSF) by Th1 cells responding to antigen and APC, but Th2 cytokine synthesis is not significantly affected. Transforming growth factor beta (TGF-beta) also inhibits IFN-gamma production, although less effectively than CSIF, whereas IL-2 and IL-4 partially antagonize the activity of CSIF. CSIF inhibition of cytokine synthesis is not complete, since early cytokine synthesis (before 8 h) is not significantly affected, whereas later synthesis is strongly inhibited. In the presence of CSIF, IFN-gamma mRNA levels are reduced slightly at 8, and strongly at 12 h after stimulation. Inhibition of cytokine expression by CSIF is not due to a general reduction in Th1 cell viability, since actin mRNA levels were not reduced, and proliferation of antigen-stimulated cells in response to IL-2, was unaffected. Biochemical characterization, mAbs, and recombinant or purified cytokines showed that CSIF is distinct from IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IFN-gamma, GM-CSF, TGF-beta, TNF, LT, and P40. The potential role of CSIF in crossregulation of Th1 and Th2 responses is discussed.
The polyclonal B cell responses induced by Trypanosoma cruzi infection last for at least 6 mo after the inoculation of the parasites. In the acute phase of the disease, B cells from spleen and lymph nodes are largely stimulated, whereas a decrease in bone marrow PFC is observed. As the disease progresses, the numbers of Ig-secreting cells in the spleen, lymph nodes, and bone marrow are all enhanced. The isotype distribution of PFC, however, remains unvariable along the course of the infection, and it is characterized by the predominance of IgG2a- and IgG2b-secreting cells. No striking difference in the isotype pattern of resistant and susceptible strains of mice was observed. The continuous and long-lasting B cell stimulation generated during the infection may have important consequences in the pathology of Chagas' disease.
The murine immune interferon (IFN-gamma) gene was cloned and expressed under control of the simian virus 40 early promoter in the monkey COS-1 cell line. A protein is secreted from these cells having the biological, antigenic, and biochemical characteristics of natural murine IFN-gamma. Cloned murine IFN-gamma cDNAs were obtained by using RNA from both mitogen-induced murine spleens and the transfected COS cells, and both code for identical proteins. The mature murine IFN-gamma encoded is 136 amino acids long, 10 amino acids shorter than human IFN-gamma. The nucleotide homology between the murine and human IFN-gamma genes is 60-65%, whereas the encoded proteins are only 40% homologous. Murine IFN-gamma cDNA was expressed in Escherichia coli under trp promoter control.
A thermostable DNA polymerase was used in an in vitro DNA amplification procedure, the polymerase chain reaction. The enzyme, isolated from Thermus aquaticus, greatly simplifies the procedure and, by enabling the amplification reaction to be performed at higher temperatures, significantly improves the specificity, yield, sensitivity, and length of products that can be amplified. Single-copy genomic sequences were amplified by a factor of more than 10 million with very high specificity, and DNA segments up to 2000 base pairs were readily amplified. In addition, the method was used to amplify and detect a target DNA molecule present only once in a sample of 10(5) cells.
Infection of several mouse strains with Trypanosoma cruzi stimulates high levels of T and B lymphocyte activities which persist during the chronic phase and is followed by specific immunosuppression and severe autoimmune pathology. Infected BALB.Xid mice carrying an X-linked mutation and lacking CD5 B cells, display poor B cell responses to T. cruzi infection, accompanied by low levels of specific and non-specific immunoglobulins in the serum. However, these animals control parasitemia, do not show the wasting observed in BALB/c mice, and develop almost no pathology early in the chronic phase. The infection of (BALB.Xid female x BALB/c male) F1 animals shows that immunodefective males behave like Xid animals in contrast to females which respond as normal BALB/c mice. These results indicate that the Xid locus controls lymphocyte responses, parasite clearance and pathology in experimental Chagas' disease.
The immunological mechanisms required to engender resistance have been defined in few infectious diseases of man, and the role of specific cytokines is unclear. Leprosy presents clinically as a spectrum in which resistance correlates with cell-mediated immunity to the pathogen. To assess in situ cytokine patterns, messenger RNA extracted from leprosy skin biopsy specimens was amplified by the polymerase chain reaction with 14 cytokine-specific primers. In lesions of the resistant form of the disease, messenger RNAs coding for interleukin-2 and interferon-gamma were most evident. In contrast, messenger RNAs for interleukin-4, interleukin-5, and interleukin-10 predominated in the multibacillary form. Thus, resistance and susceptibility were correlated with distinct patterns of cytokine production.
A powerful method to amplify reverse-transcribed RNA, the polymerase chain reaction can be used to measure cytokine gene transcription in a small number of cells, or in cases where there is low mRNA copy number. This technique may be used to obtain qualitative or quantitative determinations of cytokine gene expression. In this review we discuss the various strategies recently described for the evaluation of cytokine expression using the polymerase chain reaction.
IL-10, a cytokine produced by CD4+ T lymphocytes belonging to the Th-2 subset, has previously been shown to inhibit the synthesis of IFN-gamma by both T cells and NK cells. We now demonstrate that IL-10 can also down-regulate IFN-gamma-dependent immunity by blocking the ability of that lymphokine to activate macrophages. Thus, IL-10, in a dose-dependent manner, inhibits the microbicidal activity of IFN-gamma-treated inflammatory macrophages against intracellular Toxoplasma gondii as well as the extracellular killing of schistosomula of Schistosoma mansoni. This suppression correlates with the inhibition by IL-10 of IFN-gamma-induced production of toxic nitrogen oxide metabolites, an effector mechanism previously implicated in the killing by macrophages of both parasite targets. IL-10 inhibition of nitric oxide production was shown to occur when the cytokine is given before or together with the IFN-gamma-activating stimulus, but not after its removal from the cultures and to require 12 h of contact for maximal suppressive effect on macrophage function. These results, taken together with previous findings on the down-regulation of Th1 lymphokine production by IL-10, indicate that the induction of IL-10 may be an important strategy by which parasites evade IFN-gamma-dependent, cell-mediated immune destruction.
We have previously reported (O'Garra, A. et al., Int. Immunol. 1990, 2:821) that murine B lymphomas and purified normal peritoneal B cells produce interleukin (IL) 10. We now show that this production of IL 10 B cells correlates with the presence of Ly-1 (B-1) B cells, in both normal and diseased mice. Using a semi-quantitative modification of the polymerase chain reaction, we show that IL 10 expression is detectable in peritoneal B cells but only becomes apparent in splenic B cells of aged mice of which a high proportion are Ly-1+. Furthermore, the expression of IL 10 is constitutive in splenic B cells from mice carrying the Ly-1+ BCL1 lymphoma. Since IL 10 is a potent regulator of in vitro immune function, its production by Ly-1 lineage B (B-1) cells raises the possibility that this subset of B cells may regulate their own development and/or the function of other immunocompetent cells.
The beta 2-microglobulin (beta 2m) protein associates with the products of the class I major histocompatibility (MHC) loci; this combination functions in the thymic development of and antigen presentation to CD8+ T cells. Mice in which the beta 2m gene has been disrupted by homologous recombination fail to express class I MHC gene products, and therefore lack CD8+ T cells and measurable cytotoxic T-cell responses. However, beta 2m- mice appear to have normal development of both CD4+ alpha/beta T-cell receptor (TCR+) and gamma/delta TCR+ T cells and are not overtly more susceptible than beta 2m+ mice to potential environmental agents of infection or to experimental viral infection. Here we show that beta 2m- mice suffer high parasitaemias and early death when infected with the obligate cytoplasmic protozoan parasite Trypanosoma cruzi. Despite this increased susceptibility, the beta 2m- mice are more responsive than their beta 2m+ littermates in terms of lymphokine production, making higher levels of both interleukin-2 and interferon-gamma in response to mitogen stimulation. In addition, the beta 2m- mice show essentially no inflammatory response in parasite-infected tissues. These results confirm previous experiments on mice depleted of CD8+ cells using antibody treatment in demonstrating the importance of CD8+ T cells in immune protection in T. cruzi infection. They also implicate CD8+ T cells and/or class I MHC molecules in regulation of lymphokine production and recruitment of inflammatory cells.
Parasitic protozoa and helminths are a diverse group of organisms which together form a major cause of infectious disease in humans and livestock. Studies in animal models have revealed that T lymphocytes and the cytokines they produce play a crucial role in determining the outcome of parasitic infection in terms of both protective immunity and immunopathology. Of particular interest is recent evidence that different parasitic infections in the context of different host genetic background can trigger polarized CD4+ T cell subset responses. The set of cytokines produced by these different T helper responses, in turn, can have opposing effects on the parasite, resulting in either control of infection or promotion of disease. Moreover, cytokines produced by one CD4+ subset can block either the production and/or activity of the cytokines produced by the other subset. The establishment of this state of cross-regulation may be important for parasite survival. CD8+ T cells also appear to play a dual effector/regulatory role in parasite immunity and immunopathology, although the mechanisms underlying their induction and function are less well understood. CD(8+)-mediated cytolytic killing functions have now been demonstrated against a number of different intracellular protozoa, although IFN-gamma produced by the same effector cells may also be critical in host community. In addition to providing highly relevant models for studying the selection and immunobiologic function of T-cell subsets, research on T lymphocyte-parasite interactions is crucial for the design of effective vaccines and immunotherapies and thus has broad practical as well as theoretical ramifications.
Two normal murine B-cell subpopulations, germinal center and coelomic B cells, and at least some of the lymphomas derived from them, respond to IL-5. In the case of normal B cells, a comitogen (DxS) is required. IFN-gamma is strongly inhibitory to proliferation of the coelomic B-cell subset but not for germinal center cells or the SJL lymphomas derived from them.
In murine infection with Trypanosoma cruzi, immune responsiveness to parasite and non-parasite Ag becomes suppressed during the acute phase of infection, and this suppression is known to extend to the production of IL-2. To determine whether suppression of lymphokine production was specific for IL-2, or was a generalized phenomenon involving suppressed production of other lymphokines, we have begun an investigation of the ability of mice to produce of a number of lymphokines during infection, initially addressing this question by studying IFN-gamma production. Supernatants from Con A-stimulated spleen cells from infected resistant (C57B1/6) and susceptible (C3H) mice were assayed for IFN-gamma. Supernatants known to be suppressed with respect to IL-2 production from both mouse strains contained IFN-gamma at or above that of supernatants from normal spleen cells. Samples were assayed in an IFN bioassay to ensure that the IFN-gamma detected by ELISA was biologically active. Thus, suppression during T. cruzi infection does not extend to the production of all lymphokines. The stimulation of IFN-gamma production was confirmed by detection of IFN-gamma mRNA in unstimulated spleen cells from infected animals, and in Con A, Con A + PMA, and in some cases, parasite Ag-stimulated spleen cells from infected animals. IFN-gamma mRNA levels in mitogen-stimulated spleen cells equalled or exceeded those found in similarly stimulated normal cells. In contrast, stimulated spleen cells from infected animals had reduced levels of IL-2 mRNA relative to normal spleen cells. Thus at both the protein and mRNA level, IFN-gamma production is stimulated by T. cruzi infection, whereas IL-2 production is suppressed. Serum IFN-gamma in infected C57B1/6 and C3H mice was detected 8 days after infection, peaked on day 20 of infection, and subsequently fell, but remained detectable at low levels throughout the life of infected mice. Infected animals were depleted of cell populations known to be capable of producing IFN-gamma, and Thy-1+, CD4-, CD8-, NK- cells, and to a lesser degree, CD4+ and CD8+ cells were found to be responsible for the production of IFN-gamma during infection. We also report that IL-2 can induce IFN-gamma production in vitro and in vivo by spleen cells from infected animals, and that IL-2 can synergize with epimastigote or trypomastigote antigen to produce high levels of IFN-gamma comparable to those found in supernatants from mitogen-stimulated cells.
IL-10 inhibits the ability of macrophage but not B cell APC to stimulate cytokine synthesis by Th1 T cell clones. In this study we have examined the direct effects of IL-10 on both macrophage cell lines and normal peritoneal macrophages. LPS (or LPS and IFN-gamma)-induced production of IL-1, IL-6, and TNF-alpha proteins was significantly inhibited by IL-10 in two macrophage cell lines. Furthermore, IL-10 appears to be a more potent inhibitor of monokine synthesis than IL-4 when added at similar concentrations. LPS or LPS- and IFN-gamma-induced expression of IL-1 alpha, IL-6, or TNF-alpha mRNA was also inhibited by IL-10 as shown by semiquantitative polymerase chain reaction or Northern blot analysis. Inhibition of LPS-induced IL-6 secretion by IL-10 was less marked in FACS-purified peritoneal macrophages than in the macrophage cell lines. However, IL-6 production by peritoneal macrophages was enhanced by addition of anti-IL-10 antibodies, implying the presence in these cultures of endogenous IL-10, which results in an intrinsic reduction of monokine synthesis after LPS activation. Consistent with this proposal, LPS-stimulated peritoneal macrophages were shown to directly produce IL-10 detectable by ELISA. Furthermore, IFN-gamma was found to enhance IL-6 production by LPS-stimulated peritoneal macrophages, and this could be explained by its suppression of IL-10 production by this same population of cells. In addition to its effects on monokine synthesis, IL-10 also induces a significant change in morphology in IFN-gamma-stimulated peritoneal macrophages. The potent action of IL-10 on the macrophage, particularly at the level of monokine production, supports an important role for this cytokine not only in the regulation of T cell responses but also in acute inflammatory responses.
Expression of cytokine genes in freshly isolated T cell subsets in the autoimmune lpr mouse has been studied to determine what factors may be produced by these cells in vivo. RNA prepared from T cell subsets from diseased lpr mice and from the normal congenic strain, MRL/n, was tested for the presence of cytokine-specific message using the polymerase chain reaction. Cells of the expanded abnormal T cell subset were shown to express genes encoding interferon (IFN)-gamma, tumor necrosis factor (TNF)-beta, TNF-alpha and interleukin (IL)6, cytokines which are associated with inflammatory immune responses. These cells may thus play an important role in exacerbation of the pathological symptoms of the systemic autoimmune disease. These cells expressed no detectable IL1, IL2, IL3, IL4 or IL5. Phenotypically normal CD4+ and CD8+ T cells from both lpr and MRL/n also contained transcripts for IFN-gamma, TNF-alpha, TNF-beta and IL6. IL2 mRNA was found almost exclusively in the CD4+ subset, indicating that the CD8+ T cells in the lpr mouse are not highly activated through their class I major histocompatibility complex molecules to produce IL2, as could occur if a virus infection was inducing autoimmunity in these mice. Similar levels of IL2 mRNA were present in the CD4+ T cells of lpr and MRL/n mice, demonstrating that these cells are not defective in IL2 production in vivo.
In our study we describe further characteristics of a CD4+ T cell line (G-05) isolated from lymph nodes of C3H/HeJ mice chronically infected with Trypanosoma cruzi. This T cell line secreted lymphokines such as interleukin (IL) 4 and IL 5 and could be defined as a TH2 type of helper T cells. By passive transfer into naive mice, the G-05 line was able to induce a polyclonal B cell activation in the spleen. This splenic B cell activation was quite similar to that seen in chronically T. cruzi-infected animals, where the isotypic pattern presents a large increase of IgG2a and IgG2b isotypes. Moreover, it was possible to reproduce this kind of polyclonal B cell activation in vivo, with the supernatant of G-05 T cells cultured in the presence of T. cruzi extract, accessory cells and exogenous IL 2. Analysis of this supernatant showed the presence of large amounts of IL 4, IL 5, IL 3 and IL 6 but not of interferon-gamma, and residual IL 2 activity was not significant. These results suggest that the G-05 T cells considered as TH2 cells on the basis of their lymphokine production are involved in the development of the in vivo polyclonal B cell activation in T. cruzi infection.
Complementary DNA clones encoding mouse cytokine synthesis inhibitory factor (CSIF; interleukin-10), which inhibits cytokine synthesis by TH1 helper T cells, were isolated and expressed. The predicted protein sequence shows extensive homology with an uncharacterized open reading frame, BCRFI, in the Epstein-Barr virus genome, suggesting the possibility that this herpes virus exploits the biological activity of a captured cytokine gene to enhance its survival in the host.
Acute murine infection with T. cruzi results in polyclonal lymphocyte responses manifested by blast transformation of a large fraction of B, CD4+, and CD8+ cells. We describe here the finding of significant increases in the splenic representation of minor populations, Ly-1 + B cells and CD4-CD8- T cells. These lymphocyte populations might play an important role in the host response, as shown by T. cruzi infection of hosts that had been lethally irradiated and reconstituted with autologous bone marrow. Under these conditions, the splenic polyclonal PFC responses are nearly abrogated, and not restored by the transfer of syngeneic peritoneal cells which, however, reconstitute T15 idiotype production in the same hosts. Control levels of PFC responses, however, are reconstituted by transfer of syngeneic splenic T cells. Since bone marrow-reconstituted animals contain normal numbers of CD4+ and CD8+ T cells which are actually activated by infection, these results suggest the participation of other T cell populations in the host response to infection, as also suggested by the marked increases in T cell receptor gamma and delta messages detected in the spleen of infected animals. The implications of these findings in immunopathology of Chagas' disease are discussed.
The immunity of BALB.B mice to syngeneic Gross murine leukemia virus (MuLV)-induced B.GV cells was studied at various times after infection by Trypanosoma cruzi. BALB.B mice chronically infected by the parasite do not develop an effective immune response against B.GV tumor cells, and B.GV tumor growth in vivo is consequently facilitated. The tumor-specific cytolytic T lymphocyte (CTL) compartment in these mice was studied in vitro because CTL are known to participate actively in syngeneic tumor rejection. These analyses showed that: a) CTL differentiation is suppressed in mice with chronic T. cruzi infections; b) suppression is at the level of CTL precursor cell activation; c) suppression is not antigen-specific; and d) suppression is mediated by macrophages and Lyt-2+ T lymphocytes.
Interleukin-2 (IL-2) is a lymphokine originally described as a humoral factor required for the continued proliferation of activated T-cell clones. It also seems to be involved in the mitogenic response of thymocytes, in augmenting natural killer cell activity, in the generation of cytotoxic T cells and in the induction of other lymphokines such as gamma-interferon and a B-cell growth factor (BCGF-1). More recently, there has been evidence for the involvement of IL-2 per se in the stimulation of B-cell growth (ref. 10 and T. Kishimoto and J. Vilcek, personal communications). We have reported previously the cloning and expression of a human IL-2 complementary DNA. The cDNA encodes biologically active IL-2 which would consist of 153 amino acids, including a signal sequence. Because so much of the work on IL-2 has been done in the human and mouse, we sought to obtain cDNA encoding murine IL-2, and we now report the cloning, expression and sequence analysis of murine IL-2 cDNAs. The longest cDNA insert encodes a polypeptide of 169 amino acids, containing unique repeats of a CAG sequence which would encode 12 consecutive glutamine residues within the active IL-2 molecule.
Although the course of infection induced by L.major in mice is influenced by several factors, including the parasite virulence, the macrophage permissiveness to this parasite and response to T cell-produced lymphokines, this review has been restricted to summarizing, the recent data concerning the T-cell responses generated during infection and their effect on the disease process. Experimental evidence strongly suggests that T-cell responses play a fundamental role in resistance and susceptibility of mice to infection with L.major. It appears that resolution of lesion and exacerbation of disease result from the activity of distinct specific CD4+ T cells. There is a consensus of opinion that CD4+ T cells from the TH1 functional phenotype are generally endowed with protective function through their secreted lymphokines (e.g. IFN-gamma). However, some evidence exists that other lymphokines (e.g. TNF) might be involved in resolution of lesions. Results exist which indicate that some TH1 CD4+ T cells also contribute to susceptibility to infection. Their specificity differs from that of protective TH1 cells in the sense that these T cells might recognize parasite antigens not appropriately presented by parasitized macrophages and therefore, although releasing IFN-gamma, would not be able to concentrate this lymphokine on the surface of macrophages containing multiplying L.major. It appears that parasite-specific TH2 cells play an important role, through the IL-4 that they produce, in the severe disease seen in BALB/c mice. Determining the mechanisms responsible for the expansion of TH2 cells in genetically susceptible mice as well as assessing whether or not some parasite antigens are preferentially recognized by TH1 and TH2 cells are areas of investigation of prime importance for the rational design of a vaccine against leishmaniasis. Several observations indicate that CD8+ T cells have a role in the resolution of lesions induced by this parasite. Precise investigation of the mechanism(s) accounting for their beneficial effect might depend upon our ability to derive and maintain in vitro homogenous populations and clones of L.major-specific CD8+ T cells.
In order to characterize the role played by CD4+ T lymphocytes in the immunopathology of acute Trypanosoma cruzi infection, we compared the numbers of blood and tissue parasites and the heart inflammatory reaction in normal and anti-CD4 antibody-treated C3H mice. Treatment of mice with anti-CD4 mAb during acute infection markedly inhibited T-helper-cell-dependent activities, as measured by peritoneal macrophage activation and immunoglobulin secretion by splenic B lymphocytes. After in vivo inactivation of helper T cells, the number of blood and tissue parasites significantly increased, while the inflammatory cellular infiltrates of heart muscles diminished. Our results indicate that CD4+ T lymphocytes play a dual role in the immunopathology of acute experimental Chagas' disease.
Acute Trypanosoma cruzi infection of mice results in a very marked polyclonal activation of B and T lymphocytes, accompanied by high numbers of Ig-secreting PFC and lectin-dependent effector CTL. Treatment of mice with monoclonal anti-L3T4 antibodies from the time of infection (days 0, 4, and 8) completely suppresses the polyclonal PFC response and CTL generation. Treatment of nude mice with antibody does not alter the lipopolysaccharide-induced polyclonal PFC response, and it only modulates the isotypic profile of the PFC response to T. cruzi infection, without reducing its magnitude. Furthermore, antibody-treated, T. cruzi-infected euthymic mice do not develop the typical B cell blastogenic response, but show high numbers of activated Lyt-2+ lymphoblasts in the spleen. These results indicate that effector cell generation in T. cruzi-infected mice is predominantly helper T cell-dependent.
Complementary DNA encoding the IgG1 induction factor, the first lymphokine directed to B lymphocytes, from a murine T-cell line has been cloned using a new strategy. The putative primary amino-acid sequence was deduced from the nucleotide sequence determined. The lymphokine synthesized by the direction of this cloned cDNA has many other functions, such as production of B-cell growth factor-1 and induction of Ia on B cells.