NF kappa B regulator Bcl3 controls development and function of classical dendritic cells required for resistance to Toxoplasma gondii.

The atypical IκB family member Bcl3 associates with p50/NF-κB1 or p52/NF-κB2 homodimers in the nucleus, and positively or negatively modulates transcription in a context-dependent manner. In mice lacking Bcl3 globally or specifically in CD11c+ cells, we previously reported that Toxoplasma gondii infection is uniformly fatal and is associated with an impaired Th1 immune response. Since Bcl3 expression in dendritic cells (DC) is pivotal for antigen presentation and since classical DCs (cDC) are major antigen presenting cells, we investigated the role of Bcl3 specifically in cDCs in vivo by crossing Zbtb46 cre mice with Bcl3flx/flx mice. Bcl3flx/flx Zbtb46 cre mice were as susceptible to lethal T. gondii infection as total Bcl3-/- mice and generated poor Th1 immune responses. Consistent with this, compared to wildtype controls, splenic Xcr1+ Bcl3-deficient cDC1 cells were defective in presenting Ova antigen to OT-I cells both for Ova257-264 peptide and after infection with Ovalbumin-expressing T. gondii. Moreover, splenic CD4+ and CD8+ T cells from infected Bcl3flx/flx Zbtb46 cre mice exhibited decreased T. gondii-specific priming as revealed by both reduced cytokine production and reduced T. gondii-specific tetramer staining. In vitro differentiation of cDCs from bone marrow progenitors also revealed Bcl3-dependent cDC-specific antigen-presentation activity. Consistent with this, splenocyte single cell RNA seq (scRNAseq) in infected mice revealed Bcl3-dependent expression of genes involved in antigen processing in cDCs. We also identified by scRNAseq, a unique Bcl3-dependent hybrid subpopulation of Zbtb46+ DCs co-expressing the monocyte/macrophage transcription factor Lysozyme M. This subpopulation exhibited Bcl3-dependent expansion after infection. Likewise, by flow cytometry we identified two T. gondii-induced hybrid subpopulations of Bcl3-dependent cDC1 and cDC2 cells both expressing monocyte/macrophage markers, designated as icDC1 and icDC2. Together, our results indicate that Bcl3 in classical DCs is a major determinant of protective T cell responses and survival in T. gondii-infection.

The cytokines IL-21 and GM-CSF have opposing regulatory roles in the apoptosis of conventional dendritic cells.

Interleukin-21 (IL-21) has broad actions on T and B cells, but its actions in innate immunity are poorly understood. Here we show that IL-21 induced apoptosis of conventional dendritic cells (cDCs) via STAT3 and Bim, and this was inhibited by granulocyte-macrophage colony-stimulating factor (GM-CSF). ChIP-Seq analysis revealed genome-wide binding competition between GM-CSF-induced STAT5 and IL-21-induced STAT3. Expression of IL-21 in vivo decreased cDC numbers, and this was prevented by GM-CSF. Moreover, repetitive α-galactosylceramide injection of mice induced IL-21 but decreased GM-CSF production by natural killer T (NKT) cells, correlating with decreased cDC numbers. Furthermore, adoptive transfer of wild-type CD4+ T cells caused more severe colitis with increased DCs and interferon-γ (IFN-γ)-producing CD4+ T cells in Il21r(-/-)Rag2(-/-) mice (which lack T cells and have IL-21-unresponsive DCs) than in Rag2(-/-) mice. Thus, IL-21 and GM-CSF exhibit cross-regulatory actions on gene regulation and apoptosis, regulating cDC numbers and thereby the magnitude of the immune response.

NK cell-derived interferon-γ orchestrates cellular dynamics and the differentiation of monocytes into dendritic cells at the site of infection.

Dendritic cells (DCs), monocytes, and/or macrophages initiate host-protective immune responses to intracellular pathogens in part through interleukin-12 (IL-12) production, although the relative contribution of tissue resident versus recruited cells has been unclear. Here, we showed that after intraperitoneal infection with Toxoplasma gondii cysts, resident mononuclear phagocytes are replaced by circulating monocytes that differentiate in situ into inflammatory DCs (moDCs) and F4/80(+) macrophages. Importantly, NK cell-derived interferon-γ (IFN-γ) was required for both the loss of resident mononuclear phagocytes and the local differentiation of monocytes into macrophages and moDCs. This newly generated moDC population and not the resident DCs (or macrophages) served as the major source of IL-12 at the site of infection. Thus, NK cell-derived IFN-γ is important in both regulating inflammatory cell dynamics and in driving the local differentiation of monocytes into the cells required for initiating the immune response to an important intracellular pathogen.

Critical Role of STAT5 transcription factor tetramerization for cytokine responses and normal immune function.

Cytokine-activated STAT proteins dimerize and bind to high-affinity motifs, and N-terminal domain-mediated oligomerization of dimers allows tetramer formation and binding to low-affinity tandem motifs, but the functions of dimers versus tetramers are unknown. We generated Stat5a-Stat5b double knockin (DKI) N-domain mutant mice in which STAT5 proteins form dimers but not tetramers, identified cytokine-regulated genes whose expression required STAT5 tetramers, and defined dimer versus tetramer consensus motifs. Whereas Stat5-deficient mice exhibited perinatal lethality, DKI mice were viable; thus, STAT5 dimers were sufficient for survival. Nevertheless, STAT5 DKI mice had fewer CD4(+)CD25(+) T cells, NK cells, and CD8(+) T cells, with impaired cytokine-induced and homeostatic proliferation of CD8(+) T cells. Moreover, DKI CD8(+) T cell proliferation after viral infection was diminished and DKI Treg cells did not efficiently control colitis. Thus, tetramerization of STAT5 is critical for cytokine responses and normal immune function, establishing a critical role for STAT5 tetramerization in vivo.

TH17 cells mediate inflammation in a novel model of spontaneous experimental autoimmune lacrimal keratoconjunctivitis with neural damage.

BACKGROUND: Dry eye disease (DED) affects one third of the population worldwide. In prior studies, experimental autoimmune lacrimal keratoconjunctivitis (EALK) induced by desiccating stress in mice has been used as a model of DED. This model is complicated by a requirement for exogenous epithelial cell injury and administration of anticholinergic agents with broad immunologic effects. OBJECTIVE: We sought to develop a novel mouse model of EALK and to demonstrate the responsible pathogenic mechanisms. METHODS: CD4+CD45RBhigh naive T cells with and without CD4+CD45RBlow regulatory T cells were adoptively transferred to C57BL/10 recombination-activating gene 2 (Rag2)-/- mice. The eyes, draining lymph nodes, lacrimal glands, and surrounding tissues of mice with and without spontaneous keratoconjunctivitis were evaluated for histopathologic changes, cellular infiltration, and cytokine production in tissues and isolated cells. Furthermore, the integrity of the corneal nerves was evaluated using whole-tissue immunofluorescence imaging. Gene-deficient naive T cells or RAG2-deficient hosts were evaluated to assess the roles of IFN-γ, IL-17A, and IL-23 in disease pathogenesis. Finally, cytokine levels were determined in the tears of patients with DED. RESULTS: EALK developed spontaneously in C57BL/10 Rag2-/- mice after adoptive transfer of CD4+CD45RBhigh naive T cells and was characterized by infiltration of CD4+ T cells, macrophages, and neutrophils. In addition to lacrimal keratoconjunctivitis, mice had damage to the corneal nerve, which connects components of the lacrimal functional unit. Pathogenic T-cell differentiation was dependent on IL-23p40 and controlled by cotransferred CD4+CD45RBlow regulatory T cells. TH17 rather than TH1 CD4+ cells were primarily responsible for EALK, even though levels of both IL-17 and IFN-γ were increased in inflammatory tissues, likely because of their ability to drive expression of CXC chemokines within the cornea and the subsequent influx of myeloid cells. Consistent with the findings of this model, the tears of patients with DED had increased levels of inflammatory cytokines, including IL-17A and TNF-α. CONCLUSION: We describe a novel model of spontaneous EALK that supports a role for TH17 cells in disease pathogenesis and that will contribute to our understanding of autoimmune lacrimal keratoconjunctivitis in many human eye diseases, including DED.

The role of type I interferons in intestinal infection, homeostasis, and inflammation.

Type I interferons are a widely expressed family of effector cytokines that promote innate antiviral and antibacterial immunity. Paradoxically, they can also suppress immune responses by driving production of anti-inflammatory cytokines, and dysregulation of these cytokines can contribute to host-mediated immunopathology and disease progression. Recent studies describe their anti-inflammatory role in intestinal inflammation and the locus containing IFNAR, a heterodimeric receptor for the type I interferons has been identified as a susceptibility region for human inflammatory bowel disease. This review focuses on the role of type I IFNs in the intestine in health and disease and their emerging role as immune modulators. Clear understanding of type I IFN-mediated immune responses may provide avenues for fine-tuning existing IFN treatment for infection and intestinal inflammation.

Type I IFNs regulate effector and regulatory T cell accumulation and anti-inflammatory cytokine production during T cell-mediated colitis.

We explored the function of endogenous type I IFNs (IFN-1) in the colon using the T cell adoptive transfer model of colitis. Colon mononuclear phagocytes (MPs) constitutively produced IFN-1 in a Toll/IL-1R domain-containing adapter-inducing IFN-ß-dependent manner. Transfer of CD4(+)CD45RB(hi) T cells from wild-type (WT) or IFN-α/ß receptor subunit 1 knockout (IFNAR1(-/-)) mice into RAG(-/-) hosts resulted in similar onset and severity of colitis. In contrast, RAG(-/-) × IFNAR1(-/-) double knockout (DKO) mice developed accelerated severe colitis compared with RAG(-/-) hosts when transferred with WT CD4(+)CD45RB(hi) T cells. IFNAR signaling on host hematopoietic cells was required to delay colitis development. MPs isolated from the colon lamina propria of IFNAR1(-/-) mice produced less IL-10, IL-1R antagonist, and IL-27 compared with WT MPs. Accelerated colitis development in DKO mice was characterized by early T cell proliferation and accumulation of CD11b(+)CD103(-) dendritic cells in the mesenteric lymph nodes, both of which could be reversed by systemic administration of IL-1R antagonist (anakinra). Cotransfer of CD4(+)CD25(+) regulatory T cells (Tregs) from WT or IFNAR1(-/-) mice prevented disease caused by CD4(+)CD45RB(hi) T cells. However, WT CD4(+)CD25(+)Foxp3(GFP+) Tregs cotransferred with CD4(+)CD45RB(hi) T cells into DKO hosts failed to expand or maintain Foxp3 expression and gained effector functions in the colon. To our knowledge, these data are the first to demonstrate an essential role for IFN-1 in the production of anti-inflammatory cytokines by gut MPs and the indirect maintenance of intestinal T cell homeostasis by both limiting effector T cell expansion and promoting Treg stability.

Lymphotoxin alpha-deficient mice clear persistent rotavirus infection after local generation of mucosal IgA.

Rotavirus is a major cause of pediatric diarrheal illness worldwide. To explore the role of organized intestinal lymphoid tissues in infection by and immunity to rotavirus, lymphotoxin alpha-deficient (LTα(-/-)) mice that lack Peyer's patches and mesenteric lymph nodes were orally infected with murine rotavirus. Systemic rotavirus was cleared within 10 days in both LTα(-/-) and wild-type mice, and both strains developed early and sustained serum antirotavirus antibody responses. However, unlike wild-type mice, which resolved the intestinal infection within 10 days, LTα(-/-) mice shed fecal virus for approximately 50 days after inoculation. The resolution of fecal virus shedding occurred concurrently with induction of intestinal rotavirus-specific IgA in both mouse strains. Induction of intestinal rotavirus-specific IgA in LTα(-/-) mice correlated with the (late) appearance of IgA-producing plasma cells in the small intestine. This, together with the absence of rotavirus-specific serum IgA, implies that secretory rotavirus-specific IgA was produced locally. These findings indicate that serum IgG responses are insufficient and imply that local intestinal IgA responses are important for the clearance of rotavirus from intestinal tissues. Furthermore, they show that while LTα-dependent lymphoid tissues are important for the generation of IgA-producing B cells in the intestine, they are not absolutely required in the setting of rotavirus infection. Moreover, the induction of local IgA-producing B cell responses can occur late after infection and in an LTα-independent manner.

Differential regulation of lung homeostasis and silicosis by the TAM receptors MerTk and Axl.

Introduction: TAM receptor-mediated efferocytosis plays an important function in immune regulation and may contribute to antigen tolerance in the lungs, a site with continuous cellular turnover and generation of apoptotic cells. Some studies have identified failures in efferocytosis as a common driver of inflammation and tissue destruction in lung diseases. Our study is the first to characterize the in vivo function of the TAM receptors, Axl and MerTk, in the innate immune cell compartment, cytokine and chemokine production, as well as the alveolar macrophage (AM) phenotype in different settings in the airways and lung parenchyma. Methods: We employed MerTk and Axl defective mice to induce acute silicosis by a single exposure to crystalline silica particles (20 mg/50 µL). Although both mRNA levels of Axl and MerTk receptors were constitutively expressed by lung cells and isolated AMs, we found that MerTk was critical for maintaining lung homeostasis, whereas Axl played a role in the regulation of silica-induced inflammation. Our findings imply that MerTk and Axl differently modulated inflammatory tone via AM and neutrophil recruitment, phenotype and function by flow cytometry, and TGF-ß and CXCL1 protein levels, respectively. Finally, Axl expression was upregulated in both MerTk-/- and WT AMs, confirming its importance during inflammation. Conclusion: This study provides strong evidence that MerTk and Axl are specialized to orchestrate apoptotic cell clearance across different circumstances and may have important implications for the understanding of pulmonary inflammatory disorders as well as for the development of new approaches to therapy.

Type I interferons produced by hematopoietic cells protect mice against lethal infection by mammalian reovirus.

We defined the function of type I interferons (IFNs) in defense against reovirus strain type 1 Lang (T1L), which is a double-stranded RNA virus that infects Peyer's patches (PPs) after peroral inoculation of mice. T1L induced expression of mRNA for IFN-alpha, IFN-beta, and Mx-1 in PPs and caused localized intestinal infection that was cleared in 10 d. In contrast, T1L produced fatal systemic infection in IFNalphaR1 knockout (KO) mice with extensive cell loss in lymphoid tissues and necrosis of the intestinal mucosa. Studies of bone-marrow chimeric mice indicated an essential role for hematopoietic cells in IFN-dependent viral clearance. Dendritic cells (DCs), including conventional DCs (cDCs), were the major source of type I IFNs in PPs of reovirus-infected mice, whereas all cell types expressed the antiviral protein Mx-1. Neither NK cells nor signaling via Toll-like receptor 3 or MyD88 were essential for viral clearance. These data demonstrate a requirement for type I IFNs in the control of an intestinal viral infection and indicate that cDCs are a significant source of type I IFN production in vivo. Therefore, innate immunity in PPs is an essential component of host defense that limits systemic spread of pathogens that infect the intestinal mucosa.

Genetic deletion of chemokine receptor Ccr6 decreases atherogenesis in ApoE-deficient mice.

RATIONALE: The chemokine receptor Ccr6 is a G-protein-coupled receptor expressed on various types of leukocytes identified in mouse atherosclerotic lesions. Recent evidence suggests that both CCR6 and its ligand CCL20 are also present in human atheroma; however, their functional roles in atherogenesis remain undefined. OBJECTIVE: Our objective was to delineate the role of Ccr6 in atherogenesis in the apolipoprotein E-deficient (ApoE(-/-)) mouse model of atherosclerosis. METHODS AND RESULTS: Both Ccr6 and Ccl20 are expressed in atherosclerotic aorta from ApoE(-/-) mice. Aortic lesion area in Ccr6(-/-)ApoE(-/-) mice was ∼40% and ∼30% smaller than in Ccr6(+/+)ApoE(-/-) mice at 16 and 24 weeks of age, respectively. Transplantation of bone marrow from Ccr6(-/-) mice into ApoE(-/-) mice resulted in ∼40% less atherosclerotic lesion area than for bone marrow from Ccr6(+/+) mice; lesions in Ccr6(-/-)ApoE(-/-) mice had 44% less macrophage content than lesions in Ccr6(+/+)ApoE(-/-) mice. Ccr6 was expressed on a subset of primary mouse monocytes. Accordingly, Ccl20 induced chemotaxis of primary monocytes from wild-type but not Ccr6(-/-) mice; moreover, Ccl20 induced monocytosis in ApoE(-/-) mice in vivo. Consistent with this, we observed 30% fewer monocytes in circulating blood of Ccr6(-/-)ApoE(-/-) mice, mainly because of fewer CD11b(+)Ly6C(high) inflammatory monocytes. CONCLUSIONS: Ccr6 promotes atherosclerosis in ApoE-deficient mice, which may be due in part to Ccr6 support of normal monocyte levels in blood, as well as direct Ccr6-dependent monocyte migration.

Chemokine receptor Ccr2 is critical for monocyte accumulation and survival in West Nile virus encephalitis.

West Nile virus (WNV) is a re-emerging pathogen responsible for outbreaks of fatal meningoencephalitis in humans. Previous studies have suggested a protective role for monocytes in a mouse model of WNV infection, but the molecular mechanisms have remained unclear. In this study, we show that genetic deficiency in Ccr2, a chemokine receptor on Ly6c(hi) inflammatory monocytes and other leukocyte subtypes, markedly increases mortality due to WNV encephalitis in C57BL/6 mice; this was associated with a large and selective reduction of Ly6c(hi) monocyte accumulation in the brain. WNV infection in Ccr2(+/+) mice induced a strong and highly selective monocytosis in peripheral blood that was absent in Ccr2(-/-) mice, which in contrast showed sustained monocytopenia. When a 1:1 mixture of Ccr2(+/+) and Ccr2(-/-) donor monocytes was transferred by vein into WNV-infected Ccr2(-/-) recipient mice, monocyte accumulation in the CNS was not skewed toward either component of the mixture, indicating that Ccr2 is not required for trafficking of monocytes from blood to brain. We conclude that Ccr2 mediates highly selective peripheral blood monocytosis during WNV infection of mice and that this is critical for accumulation of monocytes in the brain.

Innate and adaptive immune correlates of vaccine and adjuvant-induced control of mucosal transmission of SIV in macaques.

Adjuvant effects on innate as well as adaptive immunity may be critical for inducing protection against mucosal HIV and simian immunodeficiency virus (SIV) exposure. We therefore studied effects of Toll-like receptor agonists and IL-15 as mucosal adjuvants on both innate and adaptive immunity in a peptide/poxvirus HIV/SIV mucosal vaccine in macaques, and made three critical observations regarding both innate and adaptive correlates of protection: (i) adjuvant-alone without vaccine antigen impacted the intrarectal SIVmac251 challenge outcome, correlating with surprisingly long-lived APOBEC3G (A3G)-mediated innate immunity; in addition, even among animals receiving vaccine with adjuvants, viral load correlated inversely with A3G levels; (ii) a surprising threshold-like effect existed for vaccine-induced adaptive immunity control of viral load, and only antigen-specific polyfunctional CD8(+) T cells correlated with protection, not tetramer(+) T cells, demonstrating the importance of T-cell quality; (iii) synergy was observed between Toll-like receptor agonists and IL-15 for driving adaptive responses through the up-regulation of IL-15Ralpha, which can present IL-15 in trans, as well as for driving the innate A3G response. Thus, strategic use of molecular adjuvants can provide better mucosal protection through induction of both innate and adaptive immunity.

The intestinal microenvironment shapes macrophage and dendritic cell identity and function.

The gut comprises the largest body interface with the environment and is continuously exposed to nutrients, food antigens, and commensal microbes, as well as to harmful pathogens. Subsets of both macrophages and dendritic cells (DCs) are present throughout the intestinal tract, where they primarily inhabit the gut-associate lymphoid tissue (GALT), such as Peyer's patches and isolated lymphoid follicles. In addition to their role in taking up and presenting antigens, macrophages and DCs possess extensive functional plasticity and these cells play complementary roles in maintaining immune homeostasis in the gut by preventing aberrant immune responses to harmless antigens and microbes and by promoting host defense against pathogens. The ability of macrophages and DCs to induce either inflammation or tolerance is partially lineage imprinted, but can also be dictated by their activation state, which in turn is determined by their specific microenvironment. These cells express several surface and intracellular receptors that detect danger signals, nutrients, and hormones, which can affect their activation state. DCs and macrophages play a fundamental role in regulating T cells and their effector functions. Thus, modulation of intestinal mucosa immunity by targeting antigen presenting cells can provide a promising approach for controlling pathological inflammation. In this review, we provide an overview on the characteristics, functions, and origins of intestinal macrophages and DCs, highlighting the intestinal microenvironmental factors that influence their functions during homeostasis. Unraveling the mechanisms by which macrophages and DCs regulate intestinal immunity will deepen our understanding on how the immune system integrates endogenous and exogenous signals in order to maintain the host's homeostasis.

Dermis resident macrophages orchestrate localized ILC2-eosinophil circuitries to maintain their M2-like properties and promote non-healing cutaneous leishmaniasis.

Tissue-resident macrophages (TRMs) are critical for tissue homeostasis/repair. We previously showed that dermal TRMs produce CCL24 (eotaxin2) which mediates their interaction with IL-4 producing eosinophils, required to maintain their number and M2-like properties in the TH1 environment of the Leishmania major infected skin. Here, we unveil another layer of TRM self-maintenance involving their production of TSLP, an alarmin typically characterized as epithelial cell-derived. Both TSLP signaling and IL-5+ innate lymphoid cell 2 (ILC2s) were shown to maintain the number of dermal TRMs and promote infection. Single cell RNA sequencing identified the dermal TRMs as the sole source of TSLP and CCL24. Development of Ccl24-cre mice permitted specific labeling of dermal TRMs, as well as interstitial TRMs from other organs. Genetic ablation of TSLP from dermal TRMs reduced the number of dermal TRMs, and disease was ameliorated. Thus, by orchestrating localized type 2 circuitries with ILC2s and eosinophils, dermal TRMs are self-maintained as a replicative niche for L. major.

Dermis resident macrophages orchestrate localized ILC2 eosinophil circuitries to promote non-healing cutaneous leishmaniasis.

Tissue-resident macrophages are critical for tissue homeostasis and repair. We previously showed that dermis-resident macrophages produce CCL24 which mediates their interaction with IL-4+ eosinophils, required to maintain their M2-like properties in the TH1 environment of the Leishmania major infected skin. Here, we show that thymic stromal lymphopoietin (TSLP) and IL-5+ type 2 innate lymphoid cells are also required to maintain dermis-resident macrophages and promote infection. Single cell RNA sequencing reveals the dermis-resident macrophages as the sole source of TSLP and CCL24. Generation of Ccl24-cre mice permits specific labeling of dermis-resident macrophages and interstitial macrophages from other organs. Selective ablation of TSLP in dermis-resident macrophages reduces the numbers of IL-5+ type 2 innate lymphoid cells, eosinophils and dermis-resident macrophages, and ameliorates infection. Our findings demonstrate that dermis-resident macrophages are self-maintained as a replicative niche for L. major by orchestrating localized type 2 circuitries with type 2 innate lymphoid cells and eosinophils.

Colitis and intestinal inflammation in IL10-/- mice results from IL-13Rα2-mediated attenuation of IL-13 activity.

BACKGROUND & AIMS: The cytokine interleukin (IL)-10 is required to maintain immune homeostasis in the gastrointestinal tract. IL-10 null mice spontaneously develop colitis or are more susceptible to induction of colitis by infections, drugs, and autoimmune reactions. IL-13 regulates inflammatory conditions; its activity might be compromised by the IL-13 decoy receptor (IL-13Rα2). METHODS: We examined the roles of IL-13 and IL-13Rα2 in intestinal inflammation in mice. To study the function of IL-13Rα2, il10(-/-) mice were crossed with il13rα2(-/-) to generate il10(-/-)il13rα2(-/-) double knockout (dKO) mice. Colitis was induced with the gastrointestinal toxin piroxicam or Trichuris muris infection. RESULTS: Induction of colitis by interferon (IFN)-γ or IL-17 in IL-10 null mice requires IL-13Rα2. Following exposure of il10(-/-) mice to piroxicam or infection with T muris, production of IL-13Rα2 increased, resulting in decreased IL-13 bioactivity and increased inflammation in response to IFN-γ or IL-17A. In contrast to il10(-/-) mice, dKO mice were resistant to piroxicam-induced colitis; they also developed less severe colitis during chronic infection with T muris infection. In both models, resistance to IFN-γ and IL-17-mediated intestinal inflammation was associated with increased IL-13 activity. Susceptibility to colitis was restored when the dKO mice were injected with monoclonal antibodies against IL-13, confirming its protective role. CONCLUSIONS: Colitis and intestinal inflammation in IL10(-/-) mice results from IL-13Rα2-mediated attenuation of IL-13 activity. In the absence of IL-13Rα2, IL-13 suppresses proinflammatory Th1 and Th17 responses. Reagents that block the IL-13 decoy receptor IL-13Rα2 might be developed for inflammatory bowel disease associated with increased levels of IFN-γ and IL-17.

CCR6 marks regulatory T cells as a colon-tropic, IL-10-producing phenotype.

Expression of CCR6 and its ligand, CCL20, are increased in the colon of humans with inflammatory bowel diseases and mice with experimental colitis; however, their role in disease pathogenesis remains obscure. In this study, we demonstrate a role for CCR6 on regulatory T (Treg) cells in the T cell-transfer model of colitis. Rag2(-/-) mice given Ccr6(-/-)CD4(+)CD45RB(high) T cells had more severe colitis with increased IFN-gamma-producing T cells, compared with the mice given wild-type cells. Although an equivalent frequency of induced/acquired Treg (iTreg) cells was observed in mesenteric lymph nodes and colon from both groups, the suppressive capacity of Ccr6(-/-) iTreg cells was impaired. Cotransfer studies of wild-type or Ccr6(-/-) Treg cells with CD4(+)CD45RB(high) T cells also showed a defect in suppression by Ccr6(-/-) Treg cells. CCR6(+) Treg cells were characterized as Ag-activated and IL-10-producing in the steady-state and preferentially migrated to the colon during inflammation. Thus, we conclude that CCR6 expression on Treg cells was required for the full function of Treg cell-mediated suppression in the T cell-transfer model of colitis. CCR6 may contribute to the regulation of colitis by directing its function in Ag-specific, IL-10-producing iTreg cells to the inflamed colon.

Luminal microvesicles uniquely influence translocating bacteria after SIV infection.

Microbial translocation contributes to persistent inflammation in both treated and untreated HIV infection. Although translocation is due in part to a disintegration of the intestinal epithelial barrier, there is a bias towards the translocation of Proteobacteria. We hypothesized that intestinal epithelial microvesicle cargo differs after HIV infection and contributes to biased translocation. We isolated gastrointestinal luminal microvesicles before and after progressive simian immunodeficiency virus (SIV) infection in rhesus macaques and measured miRNA and antimicrobial peptide content. We demonstrate that these microvesicles display decreased miR-28-5p, -484, -584-3p, and -584-5p, and let-7b-3p, as well as increased beta-defensin 1 after SIV infection. We further observed dose-dependent growth sensitivity of commensal Lactobacillus salivarius upon co-culture with isolated microvesicles. Infection-associated microvesicle differences were not mirrored in non-progressively SIV-infected sooty mangabeys. Our findings describe novel alterations of antimicrobial control after progressive SIV infection that influence the growth of translocating bacterial taxa. These studies may lead to the development of novel therapeutics for treating chronic HIV infection, microbial translocation, and inflammation.