[Show abstract][Hide abstract] ABSTRACT: Oropharyngeal candidiasis (OPC) is an opportunistic fungal infection caused by Candida albicans. OPC is frequent in HIV/AIDS, implicating adaptive immunity. Mice are naive to Candida, yet IL-17 is induced within 24 h of infection, and susceptibility is strongly dependent on IL-17R signaling. We sought to identify the source of IL-17 during the early innate response to candidiasis. We show that innate responses to Candida require an intact TCR, as SCID, IL-7Rα(-/-), and Rag1(-/-) mice were susceptible to OPC, and blockade of TCR signaling by cyclosporine induced susceptibility. Using fate-tracking IL-17 reporter mice, we found that IL-17 is produced within 1-2 d by tongue-resident populations of γδ T cells and CD3(+)CD4(+)CD44(hi)TCRβ(+)CCR6(+) natural Th17 (nTh17) cells, but not by TCR-deficient innate lymphoid cells (ILCs) or NK cells. These cells function redundantly, as TCR-β(-/-) and TCR-δ(-/-) mice were both resistant to OPC. Whereas γδ T cells were previously shown to produce IL-17 during dermal candidiasis and are known to mediate host defense at mucosal surfaces, nTh17 cells are poorly understood. The oral nTh17 population expanded rapidly after OPC, exhibited high TCR-β clonal diversity, and was absent in Rag1(-/-), IL-7Rα(-/-), and germ-free mice. These findings indicate that nTh17 and γδ T cells, but not ILCs, are key mucosal sentinels that control oral pathogens.
[Show abstract][Hide abstract] ABSTRACT: Type 2 inflammation underlies allergic diseases such as atopic dermatitis, which is characterized by the accumulation of basophils and group 2 innate lymphoid cells (ILC2s) in inflamed skin lesions. Although murine studies have demonstrated that cutaneous basophil and ILC2 responses are dependent on thymic stromal lymphopoietin, whether these cell populations interact to regulate the development of cutaneous type 2 inflammation is poorly defined. In this study, we identify that basophils and ILC2s significantly accumulate in inflamed human and murine skin and form clusters not observed in control skin. We demonstrate that murine basophil responses precede ILC2 responses and that basophils are the dominant IL-4-enhanced GFP-expressing cell type in inflamed skin. Furthermore, basophils and IL-4 were necessary for the optimal accumulation of ILC2s and induction of atopic dermatitis-like disease. We show that ILC2s express IL-4Rα and proliferate in an IL-4-dependent manner. Additionally, basophil-derived IL-4 was required for cutaneous ILC2 responses in vivo and directly regulated ILC2 proliferation ex vivo. Collectively, these data reveal a previously unrecognized role for basophil-derived IL-4 in promoting ILC2 responses during cutaneous inflammation.
Journal of immunology (Baltimore, Md. : 1950). 08/2014;
[Show abstract][Hide abstract] ABSTRACT: The paradigm that macrophages that reside in steady-state tissues are derived from embryonic precursors has never been investigated in the intestine, which contains the largest pool of macrophages. Using fate-mapping models and monocytopenic mice, together with bone marrow chimera and parabiotic models, we found that embryonic precursor cells seeded the intestinal mucosa and demonstrated extensive in situ proliferation during the neonatal period. However, these cells did not persist in the intestine of adult mice. Instead, they were replaced around the time of weaning by the chemokine receptor CCR2-dependent influx of Ly6C(hi) monocytes that differentiated locally into mature, anti-inflammatory macrophages. This process was driven largely by the microbiota and had to be continued throughout adult life to maintain a normal intestinal macrophage pool.
[Show abstract][Hide abstract] ABSTRACT: The response to influenza virus (IAV) infection and severity of disease is highly variable in humans. We hypothesized that one factor contributing to this variability is the presence of specific respiratory tract (RT) microbes. One such microbe is Streptococcus pneumoniae (Sp) that is carried asymptomatically in the RT of many humans. In a mouse co-infection model we found that in contrast to secondary bacterial infection that exacerbates disease, Sp colonization 10 days prior to IAV protects from virus-induced morbidity and lung pathology. Using mutant Sp strains, we identified a critical role for the bacterial virulence factor pneumolysin (PLY) in mediating this protection. Colonization with the PLY-sufficient Sp strain induces expression of the immune-suppressive enzyme arginase 1 in alveolar macrophages (aMø) and correlates with attenuated recruitment and function of pulmonary inflammatory cells. Our study demonstrates a novel role for PLY in Sp-mediated protection by maintaining aMø as "gatekeepers" against virus-induced immunopathology.
[Show abstract][Hide abstract] ABSTRACT: The mammalian gastrointestinal (GI) tract is colonized by trillions of beneficial commensal bacteria that are essential for promoting normal intestinal physiology. While the majority of commensal bacteria are found in the intestinal lumen, many species have also adapted to colonize different anatomical locations in the intestine, including the surface of intestinal epithelial cells (IECs) and the interior of gut-associated lymphoid tissues. These distinct tissue localization patterns permit unique interactions with the mammalian immune system and collectively influence intestinal immune cell homeostasis. Conversely, dysregulated localization of commensal bacteria can lead to inappropriate activation of the immune system and is associated with numerous chronic infectious, inflammatory, and metabolic diseases. Therefore, regulatory mechanisms that control proper anatomical containment of commensal bacteria are essential to maintain tissue homeostasis and limit pathology. In this review, we propose that commensal bacteria associated with the mammalian GI tract can be anatomically defined as (i) luminal, (ii) epithelial-associated, or (iii) lymphoid tissue-resident, and we discuss the role and regulation of these microbial populations in health and disease.
[Show abstract][Hide abstract] ABSTRACT: The recruitment of immune cells into solid tumors is an essential prerequisite of tumor development. Depending on the prevailing polarization profile of these infiltrating leucocytes, tumorigenesis is either promoted or blocked. Here, we identify IκB kinase α (IKKα) as a central regulator of a tumoricidal microenvironment during intestinal carcinogenesis. Mice deficient in IKKα kinase activity are largely protected from intestinal tumor development that is dependent on the enhanced recruitment of interferon γ (IFNγ)-expressing M1-like myeloid cells. In IKKα mutant mice, M1-like polarization is not controlled in a cell-autonomous manner but, rather, depends on the interplay of both IKKα mutant tumor epithelia and immune cells. Because therapies aiming at the tumor microenvironment rather than directly at the mutated cancer cell may circumvent resistance development, we suggest IKKα as a promising target for colorectal cancer (CRC) therapy.
[Show abstract][Hide abstract] ABSTRACT: Allergic asthma is an inflammatory disease characterized by lung eosinophilia controlled by type 2 cytokines. Cysteine proteases are potent triggers of allergic inflammation by causing barrier disruption in lung epithelial cells inducing the elevation of interleukin-5 (IL-5) and IL-13 from natural helper (NH) cells, a member of ILC2s, which leads to lung eosinophilia. In this study, we found that basophils play a crucial role in NH cell-mediated eosinophilic inflammation induced by protease allergens. Conditional deletion of basophils caused a resolution of the papain-induced eosinophilia and mucus production. Resolution of eosinophilia was also observed in mice lacking IL-4 specifically in basophils, indicating that basophil-derived IL-4 enhanced expression of the chemokine CCL11, as well as IL-5, IL-9, and IL-13 in NH cells, thus attracting eosinophils. These results demonstrate that IL-4 from basophils has an important role in the NH-derived cytokine and chemokine expression, subsequently leading to protease allergen-induced airway inflammation.
[Show abstract][Hide abstract] ABSTRACT: The abundance of innate and adaptive immune cells that reside together with trillions of beneficial commensal microorganisms in the mammalian gastrointestinal tract requires barrier and regulatory mechanisms that conserve host-microbial interactions and tissue homeostasis. This homeostasis depends on the diverse functions of intestinal epithelial cells (IECs), which include the physical segregation of commensal bacteria and the integration of microbial signals. Hence, IECs are crucial mediators of intestinal homeostasis that enable the establishment of an immunological environment permissive to colonization by commensal bacteria. In this Review, we provide a comprehensive overview of how IECs maintain host-commensal microbial relationships and immune cell homeostasis in the intestine.
[Show abstract][Hide abstract] ABSTRACT: Basophils have been implicated in promoting the early development of TH 2 cell responses in some murine models of TH 2 cytokine-associated inflammation. However, the specific role of basophils in allergic asthma remains an active area of research. Recent studies in animal models and human subjects suggest that IgE may regulate the homeostasis of human basophil populations. Here, we examine basophil populations in children with severe asthma before and during therapy with the IgE-directed monoclonal antibody omalizumab. Omalizumab therapy was associated with a significant reduction in circulating basophil numbers, a finding that was concurrent with improved clinical outcomes. The observation that circulating basophils are reduced following omalizumab therapy supports a mechanistic link between IgE levels and circulating basophil populations, and may provide new insights into one mechanism by which omalizumab improves asthma symptoms.
[Show abstract][Hide abstract] ABSTRACT: Foxp3(+) regulatory T cells (Tregs) have a well-characterized role in limiting autoimmunity and dampening deleterious immune responses. However, a potential consequence of the immunosuppressive function of Tregs can be the limitation of protective immunity to infectious pathogens. Parasitic infections are a potent stimulus for the generation of Treg responses, which may be beneficial to both the parasite and the host by promoting persistence of infection and limiting immune-mediated pathology, respectively. In this study, we explore the functional role of Tregs post-low-dose infection with the intestinal helminth parasite Trichuris muris, which yields a chronic infection because of inefficient induction of Th2 responses. Early Treg depletion postinfection resulted in expedited worm clearance, and was associated with reduced Th1-mediated inflammation of the intestinal environment. Interestingly, this protective immunity was lost, and worm burden enhanced if Tregs were depleted later once the infection was established. Early and late Treg depletion resulted in enhanced Th2 and reduced Th1 cytokine and humoral responses. Blockade of the Th2 cytokine IL-4 resulted in a moderate increase in Th1 but had no effect on worm burden. Our findings suggest that Tregs preferentially limit Th2 cell expansion, which can impact infections where clear immune polarity has not been established. Thus, the impact of Treg depletion is context and time dependent, and can be beneficial to the host in situations where Th1 responses should be limited in favor of Th2 responses.
The Journal of Immunology 02/2014; · 5.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pre-clinical studies using murine models are critical for understanding the pathophysiological mechanisms underlying immune-mediated disorders such as Eosinophilic esophagitis (EoE). In this study, an optical coherence tomography (OCT) system capable of providing three-dimensional images with axial and transverse resolutions of 5 µm and 10 µm, respectively, was utilized to obtain esophageal images from a murine model of EoE-like disease ex vivo. Structural changes in the esophagus of wild-type (Tslpr(+/+) ) and mutant (Tslpr(-/-) ) mice with EoE-like disease were quantitatively evaluated and food impaction sites in the esophagus of diseased mice were monitored using OCT. Here, the capability of OCT as a label-free imaging tool devoid of tissue-processing artifacts to effectively characterize murine EoE-like disease models has been demonstrated.
[Show abstract][Hide abstract] ABSTRACT: Apolipoprotein F (ApoF) is a sialoglycoprotein that is a component of the HDL and LDL fractions of human serum. We sought to test the hypothesis that ApoF plays an important role in atherosclerosis in mice by modulating lipoprotein function. Atherosclerosis was assessed in male low density lipoprotein receptor knockout (LDLR KO) and ApoF/LDLR double knockout (DKO) mice fed a Western diet for 16 weeks. ApoF/LDLR DKO mice showed a 39% reduction in lesional area by en face analysis of aortas (p<0.05), despite no significant differences in plasma lipid parameters. ApoF KO mice had reduced expression of Interferon alpha (IFNα) responsive genes in liver and spleen, as well as impaired macrophage activation. Interferon alpha induced gene 27 like 2a (Ifi27l2a), Oligoadenylate synthetases 2 and 3 (Oas2 and Oas3) were significantly reduced in the ApoF KO mice relative to wild type controls. These effects were attributable to hypomorphic expression of Stat2 in the ApoF KO mice, a critical gene in the Type I IFN pathway that is situated just 425 base pairs downstream of ApoF. These studies implicate STAT2 as a potentially important player in atherosclerosis, and support the growing evidence that the Type I IFN pathway may contribute to this complex disease.
[Show abstract][Hide abstract] ABSTRACT: The mammalian intestine is colonized by beneficial commensal bacteria and is a site of infection by pathogens, including helminth parasites. Helminths induce potent immunomodulatory effects, but whether these effects are mediated by direct regulation of host immunity or indirectly through eliciting changes in the microbiota is unknown. We tested this in the context of virus-helminth coinfection. Helminth coinfection resulted in impaired antiviral immunity and was associated with changes in the microbiota and STAT6-dependent helminth-induced alternative activation of macrophages. Notably, helminth-induced impairment of antiviral immunity was evident in germ-free mice, but neutralization of Ym1, a chitinase-like molecule that is associated with alternatively activated macrophages, could partially restore antiviral immunity. These data indicate that helminth-induced immunomodulation occurs independently of changes in the microbiota but is dependent on Ym1.
[Show abstract][Hide abstract] ABSTRACT: Background
Exposure to food allergens through a disrupted skin barrier has been recognized as a potential factor in the increasing prevalence of food allergy.
We sought to test the immunologic mechanisms by which epicutaneous sensitization to food allergens predisposes to intestinal food allergy.
Mice were epicutaneously sensitized with ovalbumin or peanut on an atopic dermatitis–like skin lesion, followed by intragastric antigen challenge. Antigen-specific serum IgE levels and TH2 cytokine responses were measured by ELISA. Expression of type 2 cytokines and mast cell proteases in the intestine were measured by using real-time PCR. Accumulation of basophils in the skin and mast cells in the intestine was examined by using flow cytometry. In vivo basophil depletion was achieved by using diphtheria toxin treatment of Baso-DTR mice. For cell-transfer studies, the basophil population was expanded in vivo by means of hydrodynamic tail vein injection of thymic stromal lymphopoietin (TSLP) cDNA plasmid.
Sensitization to food allergens through an atopic dermatitis–like skin lesion is associated with an expansion of TSLP-elicited basophils in the skin that promote antigen-specific TH2 cytokine responses, increased antigen-specific serum IgE levels, and accumulation of mast cells in the intestine, promoting the development of intestinal food allergy. Critically, disruption of TSLP responses or depletion of basophils reduced the susceptibility to intestinal food allergy, whereas transfer of TSLP-elicited basophils into intact skin promoted disease.
Epicutaneous sensitization on a disrupted skin barrier is associated with accumulation of TSLP-elicited basophils, which are necessary and sufficient to promote antigen-induced intestinal food allergy.
The Journal of allergy and clinical immunology 01/2014; · 12.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Extramedullary hematopoiesis (EMH) refers to the differentiation of hematopoietic stem cells (HSCs) into effector cells that occurs in compartments outside of the bone marrow. Previous studies linked pattern-recognition receptor (PRR)-expressing HSCs, EMH, and immune responses to microbial stimuli. However, whether EMH operates in broader immune contexts remains unknown. Here, we demonstrate a previously unrecognized role for thymic stromal lymphopoietin (TSLP) in promoting the population expansion of progenitor cells in the periphery and identify that TSLP-elicited progenitors differentiated into effector cells including macrophages, dendritic cells, and granulocytes and that these cells contributed to type 2 cytokine responses. The frequency of circulating progenitor cells was also increased in allergic patients with a gain-of-function polymorphism in TSLP, suggesting the TSLP-EMH pathway might operate in human disease. These data identify that TSLP-induced EMH contributes to the development of allergic inflammation and indicate that EMH is a conserved mechanism of innate immunity.
[Show abstract][Hide abstract] ABSTRACT: The development and severity of inflammatory bowel diseases and other chronic inflammatory conditions can be influenced by host genetic and environmental factors, including signals derived from commensal bacteria. However, the mechanisms that integrate these diverse cues remain undefined. Here we demonstrate that mice with an intestinal epithelial cell (IEC)-specific deletion of the epigenome-modifying enzyme histone deacetylase 3 (HDAC3(ΔIEC) mice) exhibited extensive dysregulation of IEC-intrinsic gene expression, including decreased basal expression of genes associated with antimicrobial defence. Critically, conventionally housed HDAC3(ΔIEC) mice demonstrated loss of Paneth cells, impaired IEC function and alterations in the composition of intestinal commensal bacteria. In addition, HDAC3(ΔIEC) mice showed significantly increased susceptibility to intestinal damage and inflammation, indicating that epithelial expression of HDAC3 has a central role in maintaining intestinal homeostasis. Re-derivation of HDAC3(ΔIEC) mice into germ-free conditions revealed that dysregulated IEC gene expression, Paneth cell homeostasis and intestinal barrier function were largely restored in the absence of commensal bacteria. Although the specific mechanisms through which IEC-intrinsic HDAC3 expression regulates these complex phenotypes remain to be determined, these data indicate that HDAC3 is a critical factor that integrates commensal-bacteria-derived signals to calibrate epithelial cell responses required to establish normal host-commensal relationships and maintain intestinal homeostasis.
[Show abstract][Hide abstract] ABSTRACT: Maintenance of barrier defense is an essential component of mammalian host health and survival. Most antigens encountered by the immune system enter the body through the skin or mucosal surfaces of the respiratory, gastrointestinal (GI) and urogenital tract. The vast majority of infectious microorganisms use these tissues as portals of entry. An additional feature of barrier tissues is their constitutive and ever evolving relationship with highly diverse and site-specific beneficial microbial communities referred to as the microbiota. Therefore, these tissues are charged with the formidable task of protecting the host from pathogenic challenges, while maintaining a peaceful coexistence with resident microbiota and preserving vital physiologic tissue functions. This article is protected by copyright. All rights reserved.
European Journal of Immunology 10/2013; · 4.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Basophils were discovered by Paul Ehrlich in 1879 and represent the least abundant granulocyte population in mammals. The relative rarity of basophils and their phenotypic similarities with mast cells resulted in this cell lineage being historically overlooked, both clinically and experimentally. However, recent studies in human subjects and murine systems have shown that basophils perform nonredundant effector functions and significantly contribute to the development and progression of TH2 cytokine-mediated inflammation. Although the potential functions of murine and human basophils have provoked some controversy, recent genetic approaches indicate that basophils can migrate into lymphoid tissues and, in some circumstances, cooperate with other immune cells to promote optimal TH2 cytokine responses in vivo. This article provides a brief historical perspective on basophil-related research and discusses recent studies that have identified previously unappreciated molecules and pathways that regulate basophil development, activation, and function in the context of allergic inflammation. Furthermore, we highlight the unique effector functions of basophils and discuss their contributions to the development and pathogenesis of allergic inflammation in human disease. Finally, we discuss the therapeutic potential of targeting basophils in preventing or alleviating the development and progression of allergic inflammation.
The Journal of allergy and clinical immunology 10/2013; 132(4):789-801. · 12.05 Impact Factor