-
[show abstract]
[hide abstract]
ABSTRACT: Clinically available anti-tumour necrosis factor (TNF) biologics, which inhibit both soluble (sTNF) and transmembrane forms (tmTNF) of TNF, eliminating all TNF signalling, have successfully treated autoimmune diseases including uveitis. These have potentially serious side effects such as reactivation of latent Mycobacterium tuberculosis and, therefore, more specific inhibition of TNF signalling pathways may maintain clinical efficacy while reducing adverse effects. To determine the effects of specific pharmacological inhibition of sTNF on macrophage activation and migration, we used a mouse model of uveitis (experimental autoimmune uveoretinitis; EAU). We show that selective inhibition of sTNF is sufficient to suppress EAU by limiting inflammatory CD11b(+) macrophages and CD4(+) T cell migration into the eye. However, inhibition of both sTNF and tmTNF is required to inhibit interferon-γ-induced chemokine receptor 2, CD40, major histocompatibility complex class II and nitric oxide (NO) up-regulation, and signalling via tmTNF is sufficient to mediate tissue damage. In confirmation, intravitreal inhibition of sTNF alone did not suppress disease, and inflammatory cells that migrated into the eye were activated, generating NO, thus causing structural damage to the retina. In contrast, intravitreal inhibition of both sTNF and tmTNF suppressed macrophage activation and therefore disease. We conclude that sTNF is required for inflammatory cell infiltration into target tissue, but at the tissue site inhibition of both sTNF and tmTNF is required to inhibit macrophage activation and to protect from tissue damage.
Clinical & Experimental Immunology 05/2012; 168(2):165-77. · 3.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Activation of complement occurs during autoimmune retinal and intraocular inflammatory disease as well as neuroretinal degenerative disorders. The cleavage of C5 into fragments C5a and C5b is a critical event during the complement cascade. C5a is a potent proinflammatory anaphylatoxin capable of inducing cell migration, adhesion and cytokine release, while membrane attack complex C5b-9 causes cell lysis. Therapeutic approaches to prevent complement-induced inflammation include the use of blocking monoclonal antibodies (mAb) to prevent C5 cleavage. In these current experiments, the rat anti-mouse C5 mAb (BB5·1) was utilized to investigate the effects of inhibi-tion of C5 cleavage on disease progression and severity in experimental autoimmune uveoretinitis (EAU), a model of organ-specific autoimmunity in the eye characterized by structural retinal damage mediated by infiltrating macrophages. Systemic treatment with BB5·1 results in significantly reduced disease scores compared with control groups, while local administration results in an earlier resolution of disease. In vitro, contemporaneous C5a and interferon-g signalling enhanced nitric oxide production, accompanied by down-regulation of the inhibitory myeloid CD200 receptor, contributing to cell activation. These experiments demonstrate that C5 cleavage contributes to the full expression of EAU, and that selective C5 blockade via systemic and local routes of administration can suppress disease. This presents great thera-peutic potential to protect against tissue damage during autoimmune responses in the retina or inflammation-induced degenerative disease.
Clinical & Experimental Immunology 03/2010; 159(3):303-314. · 3.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Activation of complement occurs during autoimmune retinal and intraocular inflammatory disease as well as neuroretinal degenerative disorders. The cleavage of C5 into fragments C5a and C5b is a critical event during the complement cascade. C5a is a potent proinflammatory anaphylatoxin capable of inducing cell migration, adhesion and cytokine release, while membrane attack complex C5b-9 causes cell lysis. Therapeutic approaches to prevent complement-induced inflammation include the use of blocking monoclonal antibodies (mAb) to prevent C5 cleavage. In these current experiments, the rat anti-mouse C5 mAb (BB5.1) was utilized to investigate the effects of inhibition of C5 cleavage on disease progression and severity in experimental autoimmune uveoretinitis (EAU), a model of organ-specific autoimmunity in the eye characterized by structural retinal damage mediated by infiltrating macrophages. Systemic treatment with BB5.1 results in significantly reduced disease scores compared with control groups, while local administration results in an earlier resolution of disease. In vitro, contemporaneous C5a and interferon-gamma signalling enhanced nitric oxide production, accompanied by down-regulation of the inhibitory myeloid CD200 receptor, contributing to cell activation. These experiments demonstrate that C5 cleavage contributes to the full expression of EAU, and that selective C5 blockade via systemic and local routes of administration can suppress disease. This presents great therapeutic potential to protect against tissue damage during autoimmune responses in the retina or inflammation-induced degenerative disease.
Clinical & Experimental Immunology 12/2009; 159(3):303-14. · 3.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A clear understanding of the events surrounding the selection of autoreactive T cells in the thymus and their regulation in the periphery has eluded immunologists for years. However, recent work examining the expression of tissue-specific antigens in the thymus and the biochemistry of disease associated MHC alleles has provided important clues into the generation of the autoreactive T cell repertoire in the thymus. In addition, recent studies focusing on the role of immunoregulatory cytokines and cross-reactive peptide ligands has provided information regarding both the regulation and activation of autoreactive cells in the periphery. An improved understanding of the selection and regulation of autoreactive T cells will undoubtedly aid in the development of strategies for treating autoimmune disease.
Journal of Clinical Immunology 04/2001; 21(2):74-80. · 3.08 Impact Factor
-
Nature Immunology 10/2000; 1(3):192-4. · 26.01 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: It has been suggested that the cross-reaction of a single T cell receptor with multiple different peptide ligands is a mechanism for maintaining a diverse yet compact immune repertoire. In the context of autoimmune disease it is important to understand how this property is balanced against the maintenance of self-tolerance. Specifically, whether the cross-reactivity inherent in the immune system is focused or unfocused will have important consequences for the development of autoimmune disease. If cross-reactivity is "focused," then in an immune response to a foreign antigen all T cell receptors that recognize the foreign antigen will cross-react with a specific autoantigenic peptide. However, if cross-reactivity is "unfocused," an immune response to a foreign antigen will result in the activation of a small number of self-reactive cells within a larger pool of cells specific for the foreign antigen. We have tested whether cross-reactivity is focused or unfocused by generating a panel of T cell clones that respond to two closely related ligands. W144 is an autoantigenic peptide of myelin proteolipid protein, PLP 139-151 (HSLGKWLGHPDKF), and Q144 is an altered peptide of PLP 139-151 bearing a glutamine for tryptophan substitution at position 144. The Q144-responsive clones have a broad degree of cross-reactivity with other position 144 substituted peptides. We find that despite their characteristic responses to Q144 and W144, the patterns of responses of these clones to other structurally related ligands are random, demonstrating that cross-reactivity is unfocused in the absence of selection. Maintaining a diverse range of cross-reactive interactions may limit nonspecific responses to autoantigens.
Cellular Immunology 07/2000; 202(2):88-96. · 1.97 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The autoreactive T cells that escape central tolerance and form the peripheral self-reactive repertoire determine both susceptibility to autoimmune disease and the epitope dominance of a specific autoantigen. SJL (H-2(s)) mice are highly susceptible to the induction of experimental autoimmune encephalomyelitis (EAE) with myelin proteolipid protein (PLP). The two major encephalitogenic epitopes of PLP (PLP 139-151 and PLP 178-191) bind to IA(s) with similar affinity; however, the immune response to the PLP 139-151 epitope is always dominant. The immunodominance of the PLP 139-151 epitope in SJL mice appears to be due to the presence of expanded numbers of T cells (frequency of 1/20,000 CD4(+) cells) reactive to PLP 139-151 in the peripheral repertoire of naive mice. Neither the PLP autoantigen nor infectious environmental agents appear to be responsible for this expanded repertoire, as endogenous PLP 139-151 reactivity is found in both PLP-deficient and germ-free mice. The high frequency of PLP 139-151-reactive T cells in SJL mice is partly due to lack of thymic deletion to PLP 139-151, as the DM20 isoform of PLP (which lacks residues 116-150) is more abundantly expressed in the thymus than full-length PLP. Reexpression of PLP 139-151 in the embryonic thymus results in a significant reduction of PLP 139-151-reactive precursors in naive mice. Thus, escape from central tolerance, combined with peripheral expansion by cross-reactive antigen(s), appears to be responsible for the high frequency of PLP 139-151-reactive T cells.
Journal of Experimental Medicine 04/2000; 191(5):761-70. · 13.85 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have generated a panel of cross-reactive T cells by immunizing SJL mice (I-A(s)) with Q144 peptide, an analog of an autoantigenic peptide (W144) of myelin proteolipid protein (PLP) 139-151 (HSLGKWLGHPDKF) in which W was replaced by Q at position 144. Following immunization with Q144, T cells were expanded in vitro with W144, which is a cross-reactive, suboptimal ligand, for Q144-specific T cells. The T cell clones responded to both ligands and grew normally on the peptide W144, but were hyperstimulated when activated by Q144 in vitro. This hyperstimulation results in a heteroclitic proliferative response with secretion of additional cytokines not induced by W144. Thus expansion of T cells by a suboptimal cross-reactive ligand effectively lowers the activation threshold so that the immunizing antigen becomes a hyperstimulating ligand for the clones. Surprisingly, when the T cell clones are grown on the hyperstimulating ligand Q144, some adapt by increasing their activation threshold. This desensitization results in a loss of response to a number of cross-reactive ligands and the appearance of a more specific T cell response. Long-term culture with the hyperstimulating ligand is sometimes associated with down-regulation of CD4 expression. These results provide an explanation for the common finding of T cell heteroclicity, and suggest that although the specificity and hierarchy of the response of T cells to peptides is determined by the TCR, activation threshold and effector functions are modified by exposure to cross-reactive ligands. This observation has implications for the development and regulation of autoimmune disease.
International Immunology 03/2000; 12(2):205-13. · 3.41 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Experimental autoimmune encephalomyelitis (EAE) is an animal model of the demyelinating disease multiple sclerosis. In EAE cytokines play a critical role in defining the Th1 or Th2 nature of the autoantigen directed immune response, and in propagating and regulating inflammation within the central nervous system. In this review we summarize some of the recent developments in the field of cytokine research that relate to this model of human disease, focusing principally on disease induced with the autoantigens myelin proteolipid protein and myelin oligodendrocyte protein.
Archivum Immunologiae et Therapiae Experimentalis 02/2000; 48(5):389-98. · 2.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cross-reactivity with environmental antigens has been postulated as a mechanism responsible for the induction of autoimmune disease. Experimental autoimmune encephalomyelitis is a T cell-mediated autoimmune disease model inducible in susceptible strains of laboratory animals by immunization with protein constituents of myelin. We used myelin proteolipid protein (PLP) peptide 139-151 and its analogues to define motifs to search a protein database for structural homologues of PLP139-151 and identified five peptides derived from microbial Ags that elicit immune responses that cross-react with this self peptide. Exposure of naive SJL mice to the cross-reactive environmental peptides alone was insufficient to induce autoimmune disease even when animals were treated with Ag-nonspecific stimuli (superantigen or LPS). However, immunization of SJL mice with suboptimal doses of PLP139-151 after priming with cross-reactive environmental peptides consistently induced experimental autoimmune encephalomyelitis. Furthermore, T cell lines from mice immunized with cross-reactive environmental peptides and restimulated in vitro with PLP139-151 could induce disease upon transfer into naive recipients. These data suggest that expansion by self Ag is required to break the threshold to autoimmune disease in animals primed with cross-reactive peptides.
The Journal of Immunology 11/1998; 161(7):3307-14. · 5.79 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Productive engagement of T cell receptors (TCRs) by cognate ligand (major histocompatibility complex plus peptide) leads to proliferation, differentiation, and the elaboration of effector functions. Altered peptides generated by single amino acid substitutions in the antigenic peptide have diverse effects on the outcome of the T cell response. We have generated an altered peptide (Q144) from an autoantigenic peptide of myelin proteolipid protein 139-151 by a single amino acid substitution (from tryptophan to glutamine) in the primary TCR contact at position 144 that is capable of inducing CD4(+) T cell responses in H-2(s) mice. By using a Q144-specific T cell clone (Q1.1B6), we see a hierarchy in T cell proliferation and cytokine production with various position 144 substituted peptides and have identified a peptide (L144) that hyperstimulates this T cell clone. In contrast to Q144, L144 induces maximal proliferation at 7 logs lower antigen concentration, induces greater cell death at higher antigen dose, and induces the secretion of cytokines not detected following stimulation with the cognate ligand. This heteroclitic T cell response associated with changes in cytokine profile was observed with several other T cell clones of different specificities. The L144 peptide also induces costimulation independent proliferation and cytokine production from the Q1.1B6 T cell clone. We describe this as a superagonist response. Such responses may have a role in the initiation of autoimmunity by promoting a proinflammatory environment following ligation of a cross-reactive TCR on autoreactive T cells.
Proceedings of the National Academy of Sciences 02/1998; 95(1):264-9. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We previously generated a panel of T helper cell 1 (Th1) clones specific for an encephalitogenic peptide of myelin proteolipid protein (PLP) peptide 139-151 (HSLGKWLGHPDKF) that induces experimental autoimmune encephalomyelitis (EAE) upon adoptive transfer. In spite of the differences in their T cell receptor (TCR) gene usage, all these Th1 clones required W144 as the primary and most critical TCR contact residue for the activation. In this study, we determined the TCR contact residues of a panel of Th2/Th0 clones specific for the PLP peptide 139-151 generated either by immunization with the PLP 139-151 peptide with anti- B7-1 antibody or by immunization with an altered peptide Q144. Using alanine-substituted peptide analogues of the native PLP peptide, we show that the Th2 clones have shifted their primary contact residue to the NH2-terminal end of the peptide. These Th2 cells do not show any dependence on the W144, but show a critical requirement for L141/G142 as their major TCR contact residue. Thus, in contrast with the Th1 clones that did not proliferate to A144-substituted peptide, the Th2 clones tolerated a substitution at position 144 and proliferated to A144 peptide. This alternative A144 reactive repertoire appears to have a critical role in the regulation of autoimmune response to PLP 139-151 because preimmunization with A144 to expand the L141/G142-reactive repertoire protects mice from developing EAE induced with the native PLP 139-151 peptide. These data suggest that a balance between two different T cell repertoires specific for same autoantigenic epitope can determine disease phenotype, i.e., resistance or susceptibility to an autoimmune disease.
Journal of Experimental Medicine 10/1997; 186(6):867-76. · 13.85 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) residues 139-151 (HSLGKWLGHPDKF) can be prevented by treatment with a T cell receptor (TCR) antagonist peptide (L144/R147) generated by substituting at the two principal TCR contact residues in the encephalitogenic peptide. The TCR antagonist peptide blocks activation of encephalitogenic Th1 helper cells in vitro, but the mechanisms by which the antagonist peptide blocks EAE in vivo are not clear. Immunization with L144/R147 did not inhibit generation of PLP-(139-151)-specific T cells in vivo. Furthermore, preimmunization with L144/R147 protected mice from EAE induced with the encephalitogenic peptides PLP-(178-191) and myelin oligodendrocyte protein (MOG) residues 92-106 and with mouse myelin basic protein (MBP). These data suggest that the L144/R147 peptide does not act as an antagonist in vivo but mediates bystander suppression, probably by the generation of regulatory T cells. To confirm this we generated T cell lines and clones from animals immunized with PLP-(139-151) plus L144/R147. T cells specific for L144/R147 peptide were crossreactive with the native PLP-(139-151) peptide, produced Th2/Th0 cytokines, and suppressed EAE upon adoptive transfer. These studies demonstrate that TCR antagonist peptides may have multiple biological effects in vivo. One of the principal mechanisms by which these peptides inhibit autoimmunity is by the induction of regulatory T cells, leading to bystander suppression of EAE. These results have important implications for the treatment of autoimmune diseases where there are autopathogenic responses to multiple antigens in the target organ.
Proceedings of the National Academy of Sciences 09/1997; 94(17):9279-84. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: T lymphocytes bearing alpha/beta TCR recognize antigens in the context of self MHC molecules, and this recognition leads to growth, differentiation, and effector functions. Recently, it has become clear that altered peptides generated by single amino acid substitution of the antigenic peptide can alter the patterns of differentiation and effector functions of the responding T lymphocytes. By defining the pattern of recognition and residues of the cognate ligand that bind to the TCR, altered peptide ligands (APLs) have been generated by selectively substituting the TCR contact residues in the antigenic peptide. These APLs have been utilized in vitro to study the biology of T cell function and alterations in the T cell signaling pathway. In vivo APLs have been utilized to study the mechanism of positive selection in the thymus and in regulation of autoimmune diseases. With this basic knowledge, APLs that can either hypo- or hyper-stimulate T cell function can be generated that can specifically alter (inhibit or enhance) immune responses in vivo in autoimmune diseases and cancers.
Critical Reviews in Immunology 02/1997; 17(5-6):449-62. · 3.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Many autoimmune diseases are caused by autopathogenic Th1 cells. Because in vitro Th1 and Th2 cells cross-regulate each other, it is likely that the induction of self-antigen-specific Th2 cells can prevent autoimmune disease. In the past year, investigators have further defined the role of Th1 and Th2 cytokines in the induction and regulation of autoimmunity. Furthermore, the role of MHC-antigen-T-cell avidity (strength of signal) in inducing such protective immune responses has been elucidated.
Current Opinion in Immunology 01/1997; 8(6):837-42. · 9.52 Impact Factor
-
Chemical immunology 02/1996; 63:171-86.
-
[show abstract]
[hide abstract]
ABSTRACT: In experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) peptide 139-151, we have previously shown that the disease is mediated by Th1 cells, which recognize tryptophan 144 as the primary TCR contact point. Here we describe an altered peptide ligand (APL), generated by a single amino acid substitution (tryptophan to glutamine) at position 144 (Q144), which inhibits the development of EAE induced with the native PLP 139-151 peptide (W144). We show that the APL induces T cells that are cross-reactive with the native peptide and that these cells produce Th2 (IL-4 and IL-10) and Th0 (IFN gamma and IL-10) cytokines. Adoptive transfer of T cell lines generated with the APL confer protection from EAE. These data show that changing a single amino acid in an antigenic peptide can significantly influence T cell differentiation and suggest that immune deviation may be one of the mechanisms by which APLs can inhibit an autoimmune disease.
Immunity 11/1995; 3(4):397-405. · 21.64 Impact Factor
