Innate-like Cells Research Articles

T Cell Receptor Expression Timing and Signal Strength in the Functional Differentiation of Invariant Natural Killer T Cells.

The CD1d-restricted Vα14 invariant NKT (iNKT) cell lineage in mice (Vα24 in humans) represents an evolutionary conserved innate-like immune cell type that recognizes glycolipid antigens. Because of their unique ability to promptly secrete copious amounts of both pro-inflammatory and anti-inflammatory cytokines, typically produced by different T helper cell types, iNKT cells are implicated in the regulation of various pathologic conditions such as infection, allergy, autoimmune disease, maintenance of transplantation tolerance, and cancer. This striking multifaceted role in immune regulation is correlated with the presence of multiple functionally distinct iNKT cell subsets that can be distinguished based on the expression of characteristic surface markers and transcription factors. However, to date it, remains largely unresolved how this puzzling diversity of iNKT cell functional subsets emerges and what factors dictate the type of effector cell differentiation during the thymic differentiation considering the mono-specific nature of their T cell receptor (TCR) and their selecting molecule CD1d. Here, we summarize recent findings focusing on the role of TCR-mediated signaling and discuss possible mechanisms that may influence the sub-lineage choice of iNKT cells.

The Role of IL-10 in Malaria: A Double Edged Sword.

IL-10 produced by CD4+ T cells suppresses inflammation by inhibiting T cell functions and the upstream activities of antigen presenting cells (APCs). IL-10 was first identified in Th2 cells, but has since been described in IFNγ-producing Tbet+ Th1, FoxP3+ CD4+ regulatory T (Treg) and IL-17-producing CD4+ T (Th17) cells, as well as many innate and innate-like immune cell populations. IL-10 production by Th1 cells has emerged as an important mechanism to dampen inflammation in the face of intractable infection, including in African children with malaria. However, although these type I regulatory T (Tr1) cells protect tissue from inflammation, they may also promote disease by suppressing Th1 cell-mediated immunity, thereby allowing infection to persist. IL-10 produced by other immune cells during malaria can also influence disease outcome, but the full impact of this IL-10 production is still unclear. Together, the actions of this potent anti-inflammatory cytokine along with other immunoregulatory mechanisms that emerge following Plasmodium infection represent a potential hurdle for the development of immunity against malaria, whether naturally acquired or vaccine-induced. Recent advances in understanding how IL-10 production is initiated and regulated have revealed new opportunities for manipulating IL-10 for therapeutic advantage. In this review, we will summarize our current knowledge about IL-10 production during malaria and discuss its impact on disease outcome. We will highlight recent advances in our understanding about how IL-10 production by specific immune cell subsets is regulated and consider how this knowledge may be used in drug delivery and vaccination strategies to help eliminate malaria.

Targeting of the Yersinia pestis F1 capsular antigen by innate-like B1b cells mediates a rapid protective response against bubonic plague

The generation of adaptive immunity by vaccination is usually a prolonged process that requires multiple dosing over several months. Hence, vaccines are administered for disease prevention a relatively long time prior to possible infection as opposed to post-exposure prophylaxis, which typically requires rapid intervention such as antibiotic therapy. The emergence of pathogens resistant to common antibiotic treatments has prompted the search for alternative therapeutic strategies. We previously demonstrated that vaccination of mice with the F1 capsular antigen of Yersinia pestis elicits specific and effective yet, unexpectedly, rapid anti-plague immunity. Here, we show by applying genetic and immunological approaches that the F1 antigen is targeted by peritoneal innate-like B1b cells that generate a prompt T-independent (TI) anti-F1 humoral response. The rapid F1-mediated defense response was diminished in Xid (Btkm) mice in which B1 cell numbers and activity are limited. Binding of fluorophore-labeled F1 to peritoneal B1b cells was detected as soon as 6 h post vaccination, emphasizing the high speed of this process. By assessing the ability to achieve rapid immunity with monomerized F1, we show that the natural polymeric structure of F1 is essential for (i) rapid association with peritoneal B1b cells, (ii) early induction of anti-F1 titers and (iii) rapid TI immunity in the mouse model of bubonic plague. These observations shed new light on the potential of novel as well as well-known protective antigens in generating rapid immunity and could be implemented in the rational design of future vaccines.

Graphene oxide polarizes iNKT cells for production of TGF\u03b2 and attenuates inflammation in an iNKT cell-mediated sepsis model

Graphene oxide (GO) modulates the functions of antigen-presenting cells including dendritic cells (DCs). Although carbon nanotubes affect expression of the MHC class I-like CD1d molecule, whether GO can influence immune responses of CD1d-dependent invariant natural killer T (iNKT) cells remains unclear. Here, we investigated the impact of GO on inflammatory responses mediated by α-galactosylceramide (α-GalCer), an iNKT cell agonist. We found that in vivo GO treatment substantially inhibited the capacity of α-GalCer to induce the iNKT cell-mediated trans-activation of and cytokine production by innate and innate-like cells, including DCs, macrophages, NK cells, and γδ T cells. Such effects of GO on α-GalCer-induced inflammatory responses closely correlated with iNKT cell polarization towards TGFβ production, which also explains the capacity of GO to expand regulatory T cells. Interestingly, the absence of TLR4, a receptor for GO, failed to downregulate, and instead partially enhanced the anti-inflammatory activity of GO against α-GalCer-elicited responses, implying negative effects of TLR4 signaling on the anti-inflammatory properties of GO. By employing an α-GalCer-induced sepsis model, we further demonstrated that GO treatment significantly protected mice from α-GalCer-induced lethality. Taken together, we provide strong evidence that GO holds promise as an adjuvant to modulate iNKT cell responses for immunotherapy.

Fish Lymphocytes: An Evolutionary Equivalent of Mammalian Innate-Like Lymphocytes?

Lymphocytes are the responsible of adaptive responses, as they are classically described, but evidence shows that subpopulations of mammalian lymphocytes may behave as innate-like cells, engaging non-self rapidly and without antigen presentation. The innate-like lymphocytes of mammals have been mainly identified as γδT cells and B1-B cells, exert their activities principally in mucosal tissues, may be involved in human pathologies and their functions and tissue(s) of origin are not fully understood. Due to similarities in the morphology and immunobiology of immune system between fish and mammals, and to the uniqueness of having free-living larval stages where the development can be precisely monitored and engineered, teleost fish are proposed as an experimental model to investigate human immunity. However, the homology between fish lymphocytes and mammalian innate-like lymphocytes is an issue poorly considered in comparative immunology. Increasing experimental evidence suggests that fish lymphocytes could have developmental, morphological, and functional features in common with innate-like lymphocytes of mammals. Despite such similarities, information on possible links between conventional fish lymphocytes and mammalian innate-like lymphocytes is missing. The aim of this review is to summarize and describe available findings about the similarities between fish lymphocytes and mammalian innate-like lymphocytes, supporting the hypothesis that mammalian γδT cells and B1-B cells could be evolutionarily related to fish lymphocytes.

Mast cell-driven clearance in N. brasiliensis is masked by IL-25-dependent B1 cell IgE.

Abstract A large amount of poly-specific IgE is generated during helminth infection. We have previously shown that innate-like B1 cells are responsible for this IgE production during infection with the nematode parasite Nippostrongylus brasiliensis. In vitro analysis demonstrated a novel role for IL-25-enhancement of IgE in B1 cells from helminth infected mice. In T cell-reconstituted RAG1−/− mice, N. brasiliensis clearance was enhanced with the addition of B2 cells in an IgE-dependent manner. This enhanced clearance was impeded by reconstitution with IgE sufficient B1 cells. IL-25 receptor-deficient B1 cells did not impede this clearance. Mucosal mast cells mediated the B2 cell-enhancement of clearance only in the absence of B1 cells. This was shown using mast cell depletion with anti-ckit (ACK.2) in a helminth-infected RAG1−/− reconstitution model. Additionally, gene expression analysis of the jejunum on day 7 post-inoculation found increased mast cell protease genes and mucus related genes in RAG1−/− mice reconstituted with B2 cells over T cells alone. This revealed a potential mechanism for B2 cell-enhanced clearance. Finally, R1E4, an antibody that prevents IgE from binding to FcɛRI, was administered in a model of RAG1−/− reconstitution infected with helminth and results confirmed that the B2 cell IgE/mast cell clearance enhancement was mediated through FcɛRI. Overall, these data shine new light on B2 cell derived IgE and mast cells and their role in helminth clearance that is impeded by IL-25-driven B1 cell IgE.

Control of T cell effector functions by miRNAs

The differentiation of effector T cells is a tightly regulated process that relies on the selective expression of lineage-defining master regulators that orchestrate unique transcriptional programs, including the production of distinct sets of effector cytokines. miRNAs are post-transcriptional regulators that are now viewed as critical players in these gene expression networks and help defining cell identity and function. This review summarises the role of individual miRNAs in the regulation of the differentiation of effector T cell subsets, including CD4+ T helper cells, cytotoxic CD8+ T cells and innate-like NKT cells. Moreover, we refer to miRNAs that have been identified to affect simultaneously two or more effector T cell populations, impacting on the balance between effector T cells in vivo, thus constituting potential biomarkers or targets for therapies aiming at boosting immunity or controlling autoimmunity.

Fresh Evidence for Platelets as Neuronal and Innate Immune Cells: Their Role in the Activation, Differentiation, and Deactivation of Th1, Th17, and Tregs during Tissue Inflammation

Recent studies suggest that in addition to their common function in the regulation of thrombosis and hemostasis, platelets also contribute to tissue inflammation affecting adaptive immunity. Platelets have a number of pro-inflammatory and regulatory mediators stored in their α-granules and dense granules, which are promptly released at sites of inflammation or tissue injury. Platelet-derived mediators include cytokines (IL-1α, IL-1β, and TGFβ1), chemokines (CXCL4 and CCL3), immunomodulatory neurotransmitters (serotonin, dopamine, epinephrine, histamine, and GABA), and other low-molecular-weight mediators. In addition, activated platelets synthesize a number of lipid pro-inflammatory mediators such as platelet-activating factor and prostaglandins/thromboxanes. Notably, platelets express multiple toll-like receptors and MHC class I on their surface and store IgG in their α-granules. Platelet-derived factors are highly effective in directly or indirectly modulating the priming and effector function of various subsets of T cells. Besides secreting soluble factors, activated platelets upregulate a number of integrins, adhesion molecules, and lectins, leading to the formation of platelet–T cells aggregates. Activated platelets are able to instantly release neurotransmitters acting similar to neuronal presynaptic terminals, affecting CD4 T cells and other cells in close contact with them. The formation of platelet–T cell aggregates modulates the functions of T cells via direct cell–cell contact interactions and the local release of soluble factors including neurotransmitters. New data suggest an important role for platelets as neuronal and innate-like cells that directly recognize damage- or pathogen- associated molecular patterns and instantly communicate with T cells.

B1 Cell IgE Impedes Mast Cell-Mediated Enhancement of Parasite Expulsion through B2 IgE Blockade

SUMMARYHelminth infection is known for generating large amounts of poly-specific IgE. Here we demonstrate that innate-like B1 cells are responsible for this IgE production during infection with the nematode parasites Nippostrongylus brasiliensis and Heligmosomoides polygyrus bakeri. In vitro analysis of B1 cell immunoglobulin class switch recombination to IgE demonstrated a requirement for anti-CD40 and IL-4 that was further enhanced when IL-5 was added or when the B1 source was helminth infected mice. An IL-25-induced upregulation of IgE in B1 cells was also demonstrated. In T cell-reconstituted RAG1−/− mice, N. brasiliensis clearance was enhanced with the addition of B2 cells in an IgE-dependent manner. This enhanced clearance was impeded by reconstitution with IgE sufficient B1 cells. Mucosal mast cells mediated the B2 cell enhancement of clearance in the absence of B1 cells. The data support B1 cell IgE secretion as a regulatory response exploited by the helminth.

Innate immunity and neuroinflammation

Innate-like lymphocytes emerged as an important plyaers to brigde innate and acquired immunity in a variety of immune reactions as they rapidly exert effector functions in the absence of clonal expansion. They participate the immune-regulation through rapid production of divers cytokines. Invariant natural killer (iNKT) cells and mucosal associated invariant T (MAIT) cells are members of innate-like cells which express invariant T cell receptor a chain paired with a limited set of Vb chanis. These cells are restricted by a nonpolymorphic MHC class 1b molecule, CD1and the MHC-related molecule-1 (MR1), and recognize glycolipid antigens and vitamine metabolites generated by microbiota, respectively. We previously found the regulatory role of MAIT cells in autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS) using MR1 knockout mouse and MAIT-TCR transgenic mouse. We also reported that stimulation of iNKT cells with a synthetic glycolipid prevent disease severity of EAE. We further investigated that MAIT cells and iNKT cells reduced in patients with MS, suggesting the involvement of these cells in the pathogenesis of MS.

Innate IFN-γ-Producing Cells Developing in the Absence of IL-2 Receptor Common γ-Chain.

IFN-γ is known to be predominantly produced by lymphoid cells such as certain subsets of T cells, NK cells, and other group 1 innate lymphoid cells. In this study, we used IFN-γ reporter mouse models to search for additional cells capable of secreting this cytokine. We identified a novel and rare population of nonconventional IFN-γ-producing cells of hematopoietic origin that were characterized by the expression of Thy1.2 and the lack of lymphoid, myeloid, and NK lineage markers. The expression of IFN-γ by this population was higher in the liver and lower in the spleen. Furthermore, these cells were present in mice lacking both the Rag2 and the common γ-chain (γc) genes (Rag2-/-γc-/-), indicating their innate nature and their γc cytokine independence. Rag2-/-γc-/- mice are as resistant to Mycobacterium avium as Rag2-/- mice, whereas Rag2-/- mice lacking IFN-γ are more susceptible than either Rag2-/- or Rag2-/-γc-/- These lineage-negative CD45+/Thy1.2+ cells are found within the mycobacterially induced granulomatous structure in the livers of infected Rag2-/-γc-/- animals and are adjacent to macrophages that expressed inducible NO synthase, suggesting a potential protective role for these IFN-γ-producing cells. Accordingly, Thy1.2-specific mAb administration to infected Rag2-/-γc-/- animals increased M. avium growth in the liver. Overall, our results demonstrate that a population of Thy1.2+ non-NK innate-like cells present in the liver expresses IFN-γ and can confer protection against M. avium infection in immunocompromised mice.

Multiple layers of heterogeneity and subset diversity in human MAIT cell responses to distinct microorganisms and to innate cytokines

Mucosa-associated invariant T (MAIT) cells are a large innate-like T-cell subset in humans defined by invariant TCR Vα7.2 use and expression of CD161. MAIT cells recognize microbial riboflavin metabolites of bacterial or fungal origin presented by the monomorphic MR1 molecule. The extraordinary level of evolutionary conservation of MR1 and the limited known diversity of riboflavin metabolite antigens have suggested that MAIT cells are relatively homogeneous and uniform in responses against diverse microbes carrying the riboflavin biosynthesis pathway. The ability of MAIT cells to exhibit microbe-specific functional specialization has not been thoroughly investigated. Here, we found that MAIT cell responses against Escherichia coli and Candida albicans displayed microbe-specific polyfunctional response profiles, antigen sensitivity, and response magnitudes. MAIT cell effector responses against E. coli and C. albicans displayed differential MR1 dependency and TCR β-chain bias, consistent with possible divergent antigen subspecificities between these bacterial and fungal organisms. Finally, although the MAIT cell immunoproteome was overall relatively homogenous and consistent with an effector memory-like profile, it still revealed diversity in a set of natural killer cell-associated receptors. Among these, CD56, CD84, and CD94 defined a subset with higher expression of the transcription factors promyelocytic leukemia zinc finger (PLZF), eomesodermin, and T-bet and enhanced capacity to respond to IL-12 and IL-18 stimulation. Thus, the conserved and innate-like MAIT cells harbor multiple layers of functional heterogeneity as they respond to bacterial or fungal organisms or innate cytokines and adapt their antimicrobial response patterns in a stimulus-specific manner.

B1 cell IgE impedes B2 cell IgE-mediated parasite expulsion

Abstract Helminth infection is known for generating large amounts of poly-specific IgE. Previously we reported that innate-like B1 cells are responsible for poly-specific IgE production during infection with the nematode parasites Nippostrongylus brasiliensis and Heligmosomoides polygyrus bakeri. We showed that B1 cells make large amounts of IgE. In vitro analysis of factors critical for B1 cell immunoglobulin class switch recombination to IgE demonstrated a requirement for anti-CD40 and IL-4 that further enhanced IgE production when IL-5 was added to culture or when the B1 source was helminth infected mice. We additionally reported that there was also a novel IL-25-induced upregulation of IgE in B1 cells isolated from helminth infected mice. Here, we report that in T cell reconstituted RAG1−/− mice further reconstituted with or without B1 cells and/or B2 cells and followed by infection with N. brasiliensis only B2-reconstituted mice had significantly reduced fecal egg production that was IgE dependent. Parasite clearance was impeded by reconstitution with B1 cells and was also IgE dependent. Helminth-induced B1 cell IgE was not specific for N. brasiliensis because it blocked mast cell degranulation to N. brasiliensis excretory secretory antigens in infected mice. The data supports a hypothesis that B1 cell IgE secretion has evolved as a protective response used by the helminth. In searching for a human B cell equivalent, we additionally identified a novel population of human tonsilar B cells that respond to IL-25 stimulation with increased proliferation and IgE production. We hypothesize that these cells may be important in generation of human poly-specific IgE.

Multiple layers of heterogeneity and subset diversity in human MAIT cell responses to distinct microorganisms, and to innate cytokines

Abstract Mucosa-associated invariant T (MAIT) cells are a large innate-like T cell subset in humans defined by invariant TCR Vα7.2 usage and expression of CD161. MAIT cells recognize microbial riboflavin metabolites of bacterial or fungal origin presented by the MR1 molecule. The extraordinary level of evolutionary conservation of MR1 and the limited known diversity of riboflavin metabolite antigens have suggested that MAIT cells are relatively homogeneous and uniform in responses against diverse microbes carrying the riboflavin biosynthesis pathway. The ability of MAIT cells to exhibit microbe-specific functional specialization has not been thoroughly investigated. Here, we found that MAIT cell responses against Escherichia coli and Candida albicans displayed microbe-specific polyfunctional response profiles, antigen-sensitivity and response magnitudes. MAIT cell effector responses against E. coli and C. albicans displayed differential MR1-dependency and TCR β-chain bias, consistent with possible divergent antigen sub-specificities between these microorganisms. Finally, while the MAIT cell immuno-proteome was overall relatively homogenous and consistent with an effector-memory-like profile, it still revealed diversity in a set of NK cell-associated receptors. Among these, CD56, CD84 and CD94 defined a subset with higher expression of the transcription factors promyelocytic leukemia zink finger (PLZF), Eomesodermin and T-bet and enhanced capacity to respond to IL-12 and IL-18 stimulation. Thus, the conserved and innate-like MAIT cells harbor multiple layers of functional heterogeneity as they respond to microorganisms or innate cytokines, and adapt their response patterns in a stimulus-specific manner.

Development and function of skin-homing invariant natural killer T cells

Abstract Invariant natural killer T (iNKT) cells are innate-like T cells that express restricted T cell receptors (TCR) to recognize self and foreign lipid antigens. Distinct iNKT subsets can quickly produce numerous cytokines such as interferon (IFN)-g (iNKT1), interleukin (IL)-4 (iNKT2), and IL-17 (iNKT17) to regulate immune responses in microbial infection, allergic disease, autoimmune disease and cancer. Different iNKT cell subsets have unique transcription factor profiles such as T-bet, PLZF and RORgt that determine their cytokine-producing abilities. However, mechanisms directing the tissue localization preference of different iNKT cell subsets are not well understood. Using a novel strain of CCR10-knockout (KO)/EGFP-knockin (KI) reporter mice, we found that the skin-homing chemokine receptor CCR10 is highly upregulated in iNKT cells during their thymic development stages. Analysis of cytokine production in stimulated thymic iNKT cells demonstrated that CCR10+ iNKT cells are predominantly iNKT2 cells producing IL-4, implying that iNKT2 cells are preferentially programmed in the thymus to migrate into the skin. Confirming this, CCR10-expressing iNKT2 cells are enriched in the skin at the steady state. Taken together, these findings suggest that intrathymic programming orchestrate generation of skin-homing innate-like iNKT cells with specific functional potentials to provide immediate protection of the border tissue.

Diacylglycerol Kinase ζ Limits Cytokine-dependent Expansion of CD8+ T Cells with Broad Antitumor Capacity

Interleukin-2 and -15 drive expansion/differentiation of cytotoxic CD8+ T cells that eliminate targets via antigen-independent killing. This property is clinically relevant for the improvement of T cell-based antitumor therapies. Diacylglycerol kinase α and ζ (DGKα/ζ) metabolize the diacylglycerol generated following antigen recognition by T lymphocytes. Enhanced expression of these two lipid kinases in tumor-infiltrating CD8+ T cells promotes a hyporesponsive state that contributes to tumor immune escape. Inhibition of these two enzymes might thus be of interest for potentiating conventional antigen-directed tumor elimination. In this study, we sought to characterize the contribution of DGKα and ζ to antigen-independent cytotoxic functions of CD8+ T cells. Analysis of DGKζ-deficient mice showed an increase in bystander memory-like CD8+ T cell populations not observed in DGKα-deficient mice. We demonstrate that DGKζ limits cytokine responses in an antigen-independent manner. Cytokine-specific expansion of DGKζ-deficient CD8+ T cells promoted enhanced differentiation of innate-like cytotoxic cells in vitro, and correlated with the more potent in vivo anti-tumor responses of DGKζ-deficient mice engrafted with the murine A20 lymphoma. Our studies reveal a isoform-specific function for DGKζ downstream of IL-2/IL-15-mediated expansion of innate-like cytotoxic T cells, Pharmacological manipulation of DGKζ activity is of therapeutic interest for cytokine-directed anti-tumor treatments.

Evolution of innate-like T cells and their selection by MHC class I-like molecules.

Until recently, major histocompatibility complex (MHC) class I-like-restricted innate-like αβT (iT) cells expressing an invariant or semi-invariant T cell receptor (TCR) repertoire were thought to be a recent evolutionary acquisition restricted to mammals. However, molecular and functional studies in Xenopus laevis have demonstrated that iT cells, defined as MHC class I-like-restricted innate-like αβT cells with a semi-invariant TCR, are evolutionarily conserved and prominent from early development in amphibians. As these iT cells lack the specificity conferred by conventional αβ TCRs, it is generally considered that they are specialized to recognize conserved antigens equivalent to pathogen-associated molecular patterns. Thus, one advantage offered by the MHC class I-like iT cell-based recognition system is that it can be adapted to a common pathogen and function on the basis of a relatively small number of T cells. Although iT cells have only been functionally described in mammals and amphibians, the identification of non-classical MHC/MHC class I-like genes in other groups of endothermic and ectothermic vertebrates suggests that iT cells have a broader phylogenetic distribution than previously envisioned. In this review, we discuss the possible role of iT cells during the emergence of the jawed vertebrate adaptive immune system.

Functional role of mucosal-associated invariant T cells in HIV infection.

MAIT cells represent an evolutionarily conserved, MR1-restricted, innate-like cell subset that express high levels of CD161; have a canonical semi-invariant TCR iVα7.2; and may have an important role in mucosal immunity against various bacterial and fungal pathogens. Mature MAIT cells are CD161(hi)PLZF(hi)IL-18Rα(+)iVα7.2(+)γδ-CD3(+)CD8(+) T cells and occur in the peripheral blood, liver, and mucosa of humans. MAIT cells are activated by a metabolic precursor of riboflavin synthesis presented by MR1 and, therefore, respond to many bacteria and some fungi. Despite their broad antibacterial properties, their functional role in persistent viral infections is poorly understood. Although there is an increasing line of evidence portraying the depletion of MAIT cells in HIV disease, the magnitude and the potential mechanisms underlying such depletion remain unclear. Recent studies suggest that MAIT cells are vulnerable to immune exhaustion as a consequence of HIV and hepatitis C virus infections and HIV/tuberculosis coinfections. HIV infection also appears to cause functional depletion of MAIT cells resulting from abnormal expression of T-bet and EOMES, and effective ART is unable to completely salvage functional MAIT cell loss. Depletion and exhaustion of peripheral MAIT cells may affect mucosal immunity and could increase susceptibility to opportunistic infections during HIV infection. Here, we review some of the important mechanisms associated with depletion and functional loss of MAIT cells and also suggest potential immunotherapeutic strategies to restore MAIT cell functions, including the use of IL-7 to restore effector functions in HIV disease.

Transcriptional control of RORγt across innate and adaptive immunity.

Abstract RORγt is the transcription factor responsible for the development and function of T helper 17 (Th17), γδT17, and innate lymphoid cells (ILC3s), which are key drivers of both immunity in tissues proximal to barrier surfaces and of autoimmune pathogenesis. An understanding of how regulation of the RORγt locus contributes to the programming of these separate lineages is crucial to dissecting the confounding ability of RORγt to drive such divergent responses. Examination of mice deficient in individual transcription factors that we found to constitute a key regulatory module driving Th17 cell development revealed divergent control of RORγt in innate and adaptive immune cells. This evidence suggests that distinct genomic cis-acting regulatory elements drive RORγt expression in a context dependent manner. Indeed, we found that cell-specific combinatorial usage of enhancers regulates the development and function of RORγt+ lineages in-vivo. Specifically, Th17 and ILC3 have largely unique enhancer usage while innate-like gdT17 cells share both innate and adaptive elements. We show that in vivo deletion of individual enhancer elements can modulate RORγt expression in a cell-type specific manner, the tuning of which affects cell frequency and function. Our findings provide new opportunities to study the contributions of individual RORγt+ lineages to immunity and inflammation. Moreover, these enhancers, which are highly conserved in humans, can be used to locate novel polymorphisms involved in the stratification of RORγt-dependent disease.

Helminth-induced B1 IgE is protective against allergic disease.

Abstract Helminth infection is well known for its ability to generate large amounts of non-specific IgE. This hinders the parasite-specific IgE thereby reducing mast cell (MC) degranulation and anti-helminth immunity. This study shows that the innate-like B1 cells are responsible for the substantial amounts of IgE induced during the Th2 helminth infection, Nippostrongylus brasiliensis (Nb). We utilize a mouse model with defects in hematopoiesis that results in loss of B2 cells, but retains normal B1 development, the ADAM10 transgenic mouse. These mice have equivalent IgE production in Nb when compared to wild type (WT) controls that is T cell dependent. Utilizing the NP-KLH system, we demonstrate that these mice make no antigen-specific IgG1, either high or total affinity. They additionally make no increased overall antibody when boosted with the same antigen. In WT mice, we show a population of B1 plasma cells (CD11b+CD23−B220intCD138+) in vivo, that express secreted IgE message during Nb infection. We additionally show that B1 cells (CD11b+CD23−B220int) sorted from naïve and Nb infected mice make large amounts of IgE in in vitro culture with IL-4, anti-CD40, and IL-5 by ELISA and secreted IgE message by RT-PCR. These B1 cells become CD138+ after 5 days of culture. Finally and most importantly, we show that B1 IgE is first unable to induce MC degranulation in an active cutaneous anaphylaxis model and second, it can block MC degranulation in a model of passive cutaneous anaphylaxis. Overall, these data represents a protective response that has evolved for the helminth, where non-specific B1 IgE blocks MC degranulation and thereby protects the helminth from damage. Excitingly, this could be harnessed as a potential protection against allergic disease.