Showing papers in "Nature Immunology in 2009"
TL;DR: It is shown that exhausted CD8+ T cells are subject to complex layers of negative regulation resulting from the coexpression of multiple inhibitory receptors, and regulation of T cell exhaustion by various inhibitory pathways was nonredundant.
Abstract: T cell exhaustion often occurs during chronic infection and prevents optimal viral control. The molecular pathways involved in T cell exhaustion remain poorly understood. Here we show that exhausted CD8+ T cells are subject to complex layers of negative regulation resulting from the coexpression of multiple inhibitory receptors. Exhausted CD8+ T cells expressed up to seven inhibitory receptors. Coexpression of multiple distinct inhibitory receptors was associated with greater T cell exhaustion and more severe infection. Regulation of T cell exhaustion by various inhibitory pathways was nonredundant, as blockade of the T cell inhibitory receptors PD-1 and LAG-3 simultaneously and synergistically improved T cell responses and diminished viral load in vivo. Thus, CD8+ T cell responses during chronic viral infections are regulated by complex patterns of coexpressed inhibitory receptors.
1,775 citations
TL;DR: Members of the Nod-like receptor family, including NLRP1, NLRP3 and NLRC4, and the adaptor ASC are critical components of the inflammasome that link microbial and endogenous 'danger' signals to caspase-1 activation.
Abstract: The inflammasome is a multiprotein complex that mediates the activation of caspase-1, which promotes secretion of the proinflammatory cytokines interleukin 1beta (IL-1beta) and IL-18, as well as 'pyroptosis', a form of cell death induced by bacterial pathogens. Members of the Nod-like receptor family, including NLRP1, NLRP3 and NLRC4, and the adaptor ASC are critical components of the inflammasome that link microbial and endogenous 'danger' signals to caspase-1 activation. Several diseases are associated with dysregulated activation of caspase-1 and secretion of IL-1beta. Thus, understanding inflammasome pathways may provide insight into disease pathogenesis that might identify potential targets for therapeutic intervention.
1,554 citations
TL;DR: Analysis of the T cell receptor repertoire suggested that exFoxp3 cells developed from both natural and adaptive Treg cells, suggesting the generation of potentially autoreactive effector T cells as a consequence of Foxp3 instability has important implications for understanding autoimmune disease pathogenesis.
Abstract: Regulatory T cells (T(reg) cells) are central to the maintenance of immune homeostasis. However, little is known about the stability of T(reg) cells in vivo. In this study, we demonstrate that a substantial percentage of cells had transient or unstable expression of the transcription factor Foxp3. These 'exFoxp3' T cells had an activated-memory T cell phenotype and produced inflammatory cytokines. Moreover, exFoxp3 cell numbers were higher in inflamed tissues in autoimmune conditions. Adoptive transfer of autoreactive exFoxp3 cells led to the rapid onset of diabetes. Finally, analysis of the T cell receptor repertoire suggested that exFoxp3 cells developed from both natural and adaptive T(reg) cells. Thus, the generation of potentially autoreactive effector T cells as a consequence of Foxp3 instability has important implications for understanding autoimmune disease pathogenesis.
1,170 citations
TL;DR: In a subset of CD4+ T cells, the activities of the transcription factors Foxp3 and T-bet are overlaid, which results in Treg cells with unique homeostatic and migratory properties optimized for the suppression of TH1 responses in vivo.
Abstract: Several subsets of Foxp3+ regulatory T cells are known to exist. Campbell and colleagues show that one subset of regulatory T cells requires the transcription factor T-bet during T helper type 1–mediated immune responses in vivo. Several subsets of Foxp3+ regulatory T cells (Treg cells) work in concert to maintain immune homeostasis. However, the molecular bases underlying the phenotypic and functional diversity of Treg cells remain obscure. We show that in response to interferon-γ, Foxp3+ Treg cells upregulated the T helper type 1 (TH1)-specifying transcription factor T-bet. T-bet promoted expression of the chemokine receptor CXCR3 on Treg cells, and T-bet+ Treg cells accumulated at sites of TH1 cell–mediated inflammation. Furthermore, T-bet expression was required for the homeostasis and function of Treg cells during type 1 inflammation. Thus, in a subset of CD4+ T cells, the activities of the transcription factors Foxp3 and T-bet are overlaid, which results in Treg cells with unique homeostatic and migratory properties optimized for the suppression of TH1 responses in vivo.
1,129 citations
TL;DR: These results identify distinct molecular requirements and ports of lymphocyte entry into uninflamed versus inflamed CNS and suggest that the CCR6-CCL20 axis in the choroid plexus controls immune surveillance of the CNS.
Abstract: Interleukin 17-producing T helper cells (T(H)-17 cells) are important in experimental autoimmune encephalomyelitis, but their route of entry into the central nervous system (CNS) and their contribution relative to that of other effector T cells remain to be determined. Here we found that mice lacking CCR6, a chemokine receptor characteristic of T(H)-17 cells, developed T(H)-17 responses but were highly resistant to the induction of experimental autoimmune encephalomyelitis. Disease susceptibility was reconstituted by transfer of wild-type T cells that entered into the CNS before disease onset and triggered massive CCR6-independent recruitment of effector T cells across activated parenchymal vessels. The CCR6 ligand CCL20 was constitutively expressed in epithelial cells of choroid plexus in mice and humans. Our results identify distinct molecular requirements and ports of lymphocyte entry into uninflamed versus inflamed CNS and suggest that the CCR6-CCL20 axis in the choroid plexus controls immune surveillance of the CNS.
1,081 citations
TL;DR: The differentiation of T cells producing only IL-22 was efficiently induced in naive T cells by plasmacytoid dendritic cells in an IL-6- and tumor necrosis factor–dependent way and delineate a previously unknown subset of human CD4+ effector T cells dedicated to skin pathophysiology.
Abstract: Helper T cells become polarized to effect a 'division of labor'. Sallusto and Spits and colleagues identify a new subset of skin-homing helper T cells, TH-22 cells, that secrete interleukin 22.
1,043 citations
TL;DR: The data suggest that TIGIT exerts immunosuppressive effects by binding to poliovirus receptor and modulating cytokine production by dendritic cells.
Abstract: Here we have identified a surface protein, TIGIT, containing an immunoglobulin variable domain, a transmembrane domain and an immunoreceptor tyrosine-based inhibitory motif that was expressed on regulatory, memory and activated T cells. Poliovirus receptor, which is expressed on dendritic cells, bound TIGIT with high affinity. A TIGIT-Fc fusion protein inhibited T cell activation in vitro, and this was dependent on the presence of dendritic cells. The binding of poliovirus receptor to TIGIT on human dendritic cells enhanced the production of interleukin 10 and diminished the production of interleukin 12p40. Knockdown of TIGIT with small interfering RNA in human memory T cells did not affect T cell responses. TIGIT-Fc inhibited delayed-type hypersensitivity reactions in wild-type but not interleukin 10-deficient mice. Our data suggest that TIGIT exerts immunosuppressive effects by binding to poliovirus receptor and modulating cytokine production by dendritic cells.
1,029 citations
TL;DR: This article used a system biology approach to identify early gene signatures that predicted immune responses in humans vaccinated with the yellow fever vaccine YF-17D, with up to 90% accuracy in an independent, blinded trial.
Abstract: A major challenge in vaccinology is to prospectively determine vaccine efficacy. Here we have used a systems biology approach to identify early gene 'signatures' that predicted immune responses in humans vaccinated with yellow fever vaccine YF-17D. Vaccination induced genes that regulate virus innate sensing and type I interferon production. Computational analyses identified a gene signature, including complement protein C1qB and eukaryotic translation initiation factor 2 alpha kinase 4-an orchestrator of the integrated stress response-that correlated with and predicted YF-17D CD8(+) T cell responses with up to 90% accuracy in an independent, blinded trial. A distinct signature, including B cell growth factor TNFRS17, predicted the neutralizing antibody response with up to 100% accuracy. These data highlight the utility of systems biology approaches in predicting vaccine efficacy.
1,004 citations
TL;DR: In the absence of IL-23, TH- 17 development was stalled at the early activation stage and fewer effector TH-17 cells were produced in the lymph nodes and hence available to emigrate to the bloodstream and tissues.
Abstract: Interleukin 23 (IL-23) is required for autoimmune inflammation mediated by T helper type 17 cells (TH-17 cells) and is implicated in a number of human immune disorders. Here we restricted IL-23 receptor (IL-23R) deficiency to defined cell populations in vivo to investigate the requirement for IL-23 signaling in TH-17 development and function in autoimmunity, inflammation, and infection. In the absence of IL-23, TH-17 development was ‘stalled’ at the early activation stage. TH-17 cells failed to downregulate IL-2 and the tumor necrosis factor receptor superfamily member CD27, to maintain IL-17 production and to upregulate IL-7Rα expression. These defects were associated with reduced proliferation and reduced numbers of effector TH-17 cells that exit lymph nodes destined for the bloodstream and tissues.
1,002 citations
TL;DR: A unique memory T cell subset present after acute infection with herpes simplex virus that remained resident in the skin and in latently infected sensory ganglia is described, representing an example of tissue-resident memory T cells that can provide protective immunity at points of pathogen entry.
Abstract: Effective immunity is dependent on long-surviving memory T cells. Various memory subsets make distinct contributions to immune protection, especially in peripheral infection. It has been suggested that T cells in nonlymphoid tissues are important during local infection, although their relationship with populations in the circulation remains poorly defined. Here we describe a unique memory T cell subset present after acute infection with herpes simplex virus that remained resident in the skin and in latently infected sensory ganglia. These T cells were in disequilibrium with the circulating lymphocyte pool and controlled new infection with this virus. Thus, these cells represent an example of tissue-resident memory T cells that can provide protective immunity at points of pathogen entry.
1,000 citations
TL;DR: A systematic proteomics screen for proteins that associate with DNA, 'crossed' to a screen for transcripts induced by interferon-β identified AIM2 as a candidate cytoplasmic DNA sensor for the inflammasome, which showed specificity for double-stranded DNA.
Abstract: Cytoplasmic DNA triggers activation of the innate immune system. Although 'downstream' signaling components have been characterized, the DNA-sensing components remain elusive. Here we present a systematic proteomics screen for proteins that associate with DNA, 'crossed' to a screen for transcripts induced by interferon-beta, which identified AIM2 as a candidate cytoplasmic DNA sensor. AIM2 showed specificity for double-stranded DNA. It also recruited the inflammasome adaptor ASC and localized to ASC 'speckles'. A decrease in AIM2 expression produced by RNA-mediated interference impaired DNA-induced maturation of interleukin 1beta in THP-1 human monocytic cells, which indicated that endogenous AIM2 is required for DNA recognition. Reconstitution of unresponsive HEK293 cells with AIM2, ASC, caspase-1 and interleukin 1beta showed that AIM2 was sufficient for inflammasome activation. Our data suggest that AIM2 is a cytoplasmic DNA sensor for the inflammasome.
TL;DR: A previously uncharacterized IL-22-producing human helper T cell population that coexpressed the chemokine receptor CCR6 and the skin-homing receptors CCR4 and CCR10 is described, which may be important in skin homeostasis and pathology.
Abstract: Interleukin 22 (IL-22) is a member of the IL-10 cytokine family that is involved in inflammatory and wound healing processes. Originally considered a T helper type 1 (T(H)1)-associated cytokine, IL-22 has since been shown to be produced mainly by IL-17-producing helper T cells (T(H)-17 cells). Here we describe a previously uncharacterized IL-22-producing human helper T cell population that coexpressed the chemokine receptor CCR6 and the skin-homing receptors CCR4 and CCR10. These cells were distinct from both T(H)-17 cells and T(H)1 cells. Downregulation of either the aryl hydrocarbon receptor (AHR) or the transcription factor RORC by RNA-mediated interference affected IL-22 production, whereas IL-17 production was affected only by downregulation of RORC by RNA-mediated interference. AHR agonists substantially altered the balance of IL-22- versus IL-17-producing cells. This subset of IL-22-producing cells may be important in skin homeostasis and pathology.
TL;DR: A novel DNA-sensing pathway involving RNA polymerase III and RIG-I is identified, which was important in the sensing of Epstein-Barr virus–encoded small RNAs, which were transcribed by RNA polymer enzyme III and then triggered Rig-I activation.
Abstract: After binding double-stranded RNA, RIG-I induces production of type 1 interferon. Hornung and colleagues find that RIG-I detects viral DNA via double-stranded RNA intermediates generated by RNA polymerase III.
TL;DR: It is shown that interleukin 10 produced by CD11b+ myeloid cells in recombination-activating gene 1–deficient recipient mice was needed to prevent the colitis induced by transferred CD4+CD45RBhi T cells.
Abstract: Regulatory T cells (T(reg) cells) that express the transcription factor Foxp3 suppress the activity of other cells. Here we show that interleukin 10 (IL-10) produced by CD11b(+) myeloid cells in recombination-activating gene 1-deficient (Rag1(-/-)) recipient mice was needed to prevent the colitis induced by transferred CD4(+)CD45RB(hi) T cells. In Il10(-/-)Rag1(-/-) mice, T(reg) cells failed to maintain Foxp3 expression and regulatory activity. The loss of Foxp3 expression occurred only in recipients with colitis, which indicates that the requirement for IL-10 is manifested in the presence of inflammation. IL-10 receptor-deficient (Il10rb(-/-)) T(reg) cells also failed to maintain Foxp3 expression, which suggested that host IL-10 acted directly on the T(reg) cells. Our data indicate that IL-10 released from myeloid cells acts in a paracrine manner on T(reg) cells to maintain Foxp3 expression.
TL;DR: It is concluded that human cells utilize the ubiquitin system and NDP52 to activate autophagy against bacteria attempting to colonize their cytosol.
Abstract: Cell-autonomous innate immune responses against bacteria attempting to colonize the cytosol of mammalian cells are incompletely understood. Polyubiquitylated proteins can accumulate on the surface of such bacteria, and bacterial growth is restricted by Tank-binding kinase (TBK1). Here we show that NDP52, not previously known to contribute to innate immunity, recognizes ubiquitin-coated Salmonella enterica in human cells and, by binding the adaptor proteins Nap1 and Sintbad, recruits TBK1. Knockdown of NDP52 and TBK1 facilitated bacterial proliferation and increased the number of cells containing ubiquitin-coated salmonella. NDP52 also recruited LC3, an autophagosomal marker, and knockdown of NDP52 impaired autophagy of salmonella. We conclude that human cells utilize the ubiquitin system and NDP52 to activate autophagy against bacteria attempting to colonize their cytosol.
TL;DR: Evidence is provided that signals from the commensal microflora contribute to the differentiation of a lymphocyte population coexpressing stimulatory natural killer cell receptors and the transcription factor RORγt that produced interleukin 22 (IL-22).
Abstract: The mucosal immune system of the intestine is separated from a vast array of microbes by a single layer of epithelial cells. Cues from the commensal microflora are needed to maintain epithelial homeostasis, but the molecular and cellular identities of these cues are unclear. Here we provide evidence that signals from the commensal microflora contribute to the differentiation of a lymphocyte population coexpressing stimulatory natural killer cell receptors and the transcription factor RORgammat that produced interleukin 22 (IL-22). The emergence of these IL-22-producing RORgammathiNKp46+NK1.1(int) cells depended on RORgammat expression, which indicated that these cells may have been derived from lymphoid tissue-inducer cells. IL-22 released by these cells promoted the production of antimicrobial molecules important in the maintenance of mucosal homeostasis.
TL;DR: It is shown that CD4+ follicular helper T cells constituted essentially all of the cytokine-secreting T cells in lymph nodes and were functionally distinct from T cells secreting the same cytokine in peripheral tissues.
Abstract: High-affinity antibodies are critical for host protection and underlie successful vaccines. The generation of such antibodies requires T cell-dependent help, which mediates germinal center reactions in which mutation and selection of B cells occurs. Using an interleukin 4-reporter system, we show here that CD4(+) follicular helper T cells constituted essentially all of the cytokine-secreting T cells in lymph nodes and were functionally distinct from T cells secreting the same cytokine in peripheral tissues. Follicular helper T cells with different cytokine profiles could be isolated as conjugates with B cells undergoing cytokine-specific immunoglobulin class switching with evidence of somatic hypermutation. Our findings support a model in which B cells compete for cytokines produced by follicular helper T cells that shape the affinity and isotype of the antibody response.
TL;DR: The progression of tuberculosis from a latent, subclinical infection to active disease that culminates in the transmission of infectious bacilli is determined locally at the level of the granuloma, and it is indicated that pathogen-induced dysregulation of host lipid synthesis and sequestration serves a critical role in this transition.
Abstract: The progression of tuberculosis from a latent, subclinical infection to active disease that culminates in the transmission of infectious bacilli is determined locally at the level of the granuloma. This progression takes place even in the face of a robust immune response that, although it contains infection, is unable to eliminate the bacterium. The factors or environmental conditions that influence this progression remain to be determined. Recent advances have indicated that pathogen-induced dysregulation of host lipid synthesis and sequestration serves a critical role in this transition. The foamy macrophage seems to be a key participant in both sustaining persistent bacteria and contributing to the tissue pathology that leads to cavitation and the release of infectious bacilli.
TL;DR: IL-17A-mediated protection in the CD45RBhi transfer model of colitis is demonstrated and T cells are identified as not only the source but also a target of IL-17 in vivo.
Abstract: Interleukin 23 (IL-23) and IL-17 have been linked to the pathogenesis of several chronic inflammatory disorders, including inflammatory bowel disease. Yet as an important function for IL-23 is emerging, the function of IL-17 in inflammatory bowel disease remains unclear. Here we demonstrate IL-17A-mediated protection in the CD45RBhi transfer model of colitis. An accelerated wasting disease elicited by T cells deficient in IL-17A correlated with higher expression of genes encoding T helper type 1-type cytokines in colon tissue. IL-17A also modulated T helper type 1 polarization in vitro. Furthermore, T cells deficient in the IL-17 receptor elicited an accelerated, aggressive wasting disease relative to that elicited by wild-type T cells in recipient mice. Our data demonstrate a protective function for IL-17 and identify T cells as not only the source but also a target of IL-17 in vivo.
TL;DR: A TH-17 cell–associated microRNA, miR-326, is identified whose expression was highly correlated with disease severity in patients with multiple sclerosis and mice with experimental autoimmune encephalomyelitis, and its overexpression led to more TH- 17 cells and severe EAE.
Abstract: Interleukin 17 (IL-17)-producing T helper cells (T H -17 cells) are increasingly recognized as key participants in various autoimmune diseases, including multiple sclerosis. Although sets of transcription factors and cytokines are known to regulate T H -17 differentiation, the role of noncoding RNA is poorly understood. Here we identify a T H -17 cell–associated microRNA, miR-326, whose expression was highly correlated with disease severity in patients with multiple sclerosis and mice with experimental autoimmune encephalomyelitis (EAE). In vivo silencing of miR-326 resulted in fewer T H -17 cells and mild EAE, and its overexpression led to more T H -17 cells and severe EAE. We also found that miR-326 promoted T H -17 differentiation by targeting Ets-1, a negative regulator of T H -17 differentiation. Our data show a critical role for microRNA in T H -17 differentiation and the pathogenesis of multiple sclerosis.
TL;DR: The data suggest that ICOS-induced c-Maf regulates IL-21 production that in turn regulates the expansion of TH-17 and TFH cells.
Abstract: The inducible costimulatory molecule ICOS has been suggested to be important in the development of interleukin 17 (IL-17)-producing helper T cells (T(H)-17 cells) and of follicular helper T cells (T(FH) cells). Here we show that ICOS-deficient mice had no defect in T(H)-17 differentiation but had fewer T(H)-17 cells after IL-23 stimulation and fewer T(FH) cells. We also show that T(FH) cells produced IL-17 and that T(FH) cells in ICOS-deficient mice were defective in IL-17 production. Both T(H)-17 and T(FH) cells had higher expression of the transcription factor c-Maf. Genetic loss of c-Maf resulted in a defect in IL-21 production and fewer T(H)-17 and T(FH) cells. Thus our data suggest that ICOS-induced c-Maf regulates IL-21 production that in turn regulates the expansion of T(H)-17 and T(FH) cells.
TL;DR: It is shown that CD103+ DCs were the migratory subset most efficient at processing viral antigens into the major histocompatibility complex class I pathway, potentially through cross-presentation.
Abstract: Skin-derived dendritic cells (DCs) include Langerhans cells, classical dermal DCs and a langerin-positive CD103(+) dermal subset. We examined their involvement in the presentation of skin-associated viral and self antigens. Only the CD103(+) subset efficiently presented antigens of herpes simplex virus type 1 to naive CD8(+) T cells, although all subsets presented these antigens to CD4(+) T cells. This showed that CD103(+) DCs were the migratory subset most efficient at processing viral antigens into the major histocompatibility complex class I pathway, potentially through cross-presentation. This was supported by data showing only CD103(+) DCs efficiently cross-presented skin-derived self antigens. This indicates CD103(+) DCs are the main migratory subtype able to cross-present viral and self antigens, which identifies another level of specialization for skin DCs.
TL;DR: PD-1–PD-L1 interactions maintain peripheral tolerance by mechanisms fundamentally distinct from those of CTLA-4, shows here that unlike naive or activated islet antigen–specific T cells, tolerized islets moved freely and did not swarm around antigen-bearing dendritic cells (DCs) in pancreatic lymph nodes.
Abstract: Programmed death 1 (PD-1) is an inhibitory molecule expressed on activated T cells; however, the biological context in which PD-1 controls T cell tolerance remains unclear. Using two-photon laser-scanning microscopy, we show here that unlike naive or activated islet antigen-specific T cells, tolerized islet antigen-specific T cells moved freely and did not swarm around antigen-bearing dendritic cells (DCs) in pancreatic lymph nodes. Inhibition of T cell antigen receptor (TCR)-driven stop signals depended on continued interactions between PD-1 and its ligand, PD-L1, as antibody blockade of PD-1 or PD-L1 resulted in lower T cell motility, enhanced T cell-DC contacts and caused autoimmune diabetes. Blockade of the immunomodulatory receptor CTLA-4 did not alter T cell motility or abrogate tolerance. Thus, PD-1-PD-L1 interactions maintain peripheral tolerance by mechanisms fundamentally distinct from those of CTLA-4.
TL;DR: The function of Nod2 as a viral PRR highlights the important function ofNod2 in host antiviral defense mechanisms.
Abstract: Pattern recognition receptors (PRRs) including Toll-like receptors (TLRs) and RIG like helicase (RLH) receptors are involved in innate immune antiviral responses. Here we show that nucleotide-binding oligomerization domain 2 (NOD2) can also function as a cytoplasmic viral PRR by triggering activation of interferon regulatory factor-3 (IRF3) and production of interferon-β (IFN). Following recognition of viral ssRNA genome, NOD2 utilized the adaptor protein MAVS (mitochondrial antiviral signaling) to activate IRF3. NOD2-deficient mice failed to produce IFN efficiently and exhibited enhanced susceptibility to virus-induced pathogenesis. Thus, the function of NOD2 as a viral PRR highlights the important role of NOD2 in host antiviral defense mechanisms.
TL;DR: In this article, the authors identify human lymphoid tissue-inducer cells (LTi cells) as lineage-negative RORC+ CD127+ cells with the functional ability to interact with mesenchymal cells through lymphotoxin and tumor necrosis factor.
Abstract: Mouse lymphoid tissue–inducer (LTi) cells require the transcription factor RORγt. Cupedo's group identifies RORγt+ human LTi cell equivalents as committed natural killer cell precursors, and teams led by Vivier and Diefenbach describe RORγt-expressing interleukin 22–producing natural killer cells in mouse gut. The human body contains over 500 individual lymph nodes, yet the biology of their formation is poorly understood. Here we identify human lymphoid tissue–inducer cells (LTi cells) as lineage-negative RORC+ CD127+ cells with the functional ability to interact with mesenchymal cells through lymphotoxin and tumor necrosis factor. Human LTi cells were committed natural killer (NK) cell precursors that produced interleukin 17 (IL-17) and IL-22. In vitro, LTi cells gave rise to RORC+ CD127+ NK cells that retained the ability to produce IL-17 and IL-22. Postnatally, similar populations of LTi cell–like cells and RORC+ CD127+ NK cells were present in tonsils, and both secreted IL-17 and IL-22 but no interferon-γ. Our data indicate that lymph node organogenesis is controlled by an NK cell precursor population with adaptive immune features and demonstrate a previously unappreciated link between the innate and adaptive immune systems.
TL;DR: It is shown that although dendritic cells were dispensable for allergen-induced activation of TH2 responses in vitro and in vivo, antigen presentation by basophils was necessary and sufficient for this.
Abstract: T helper type 2 (T(H)2)-mediated immune responses are induced after infection with multicellular parasites and can be triggered by a variety of allergens. The mechanisms of induction and the antigen-presenting cells involved in the activation of T(H)2 responses remain poorly defined, and the innate immune sensing pathways activated by parasites and allergens are largely unknown. Basophils are required for the in vivo induction of T(H)2 responses by protease allergens. Here we show that basophils also function as antigen-presenting cells. We show that although dendritic cells were dispensable for allergen-induced activation of T(H)2 responses in vitro and in vivo, antigen presentation by basophils was necessary and sufficient for this. Thus, basophils function as antigen-presenting cells for T(H)2 differentiation in response to protease allergens.
TL;DR: A new mouse model of memory B cell labeling dependent on the cytidine deaminase AID is used, which shows that after immunization with a particulate antigen, B cell memory appeared in several subsets, comprising clusters of immunoglobulin M–positive and IgG1+ B cells in germinal center–like structures that persisted up to 8 months after immunized.
Abstract: Memory B cells are at the center of longstanding controversies regarding the presence of antigen for their survival and their re-engagement in germinal centers after secondary challenge. Using a new mouse model of memory B cell labeling dependent on the cytidine deaminase AID, we show that after immunization with a particulate antigen, B cell memory appeared in several subsets, comprising clusters of immunoglobulin M-positive (IgM(+)) and IgG1(+) B cells in germinal center-like structures that persisted up to 8 months after immunization, as well as IgM(+) and IgG1(+) B cells with a memory phenotype outside of B cell follicles. After challenge, the IgG subset differentiated into plasmocytes, whereas the IgM subset reinitiated a germinal center reaction. This model, in which B cell memory appears in several layers with different functions, reconciles previous conflicting propositions.
TL;DR: The cytokine profiles of peripheral γδ T cells are predetermined mainly by a mechanism involving CD27, and these phenotypes were established during thymic development.
Abstract: The production of cytokines such as interferon-gamma and interleukin 17 by alphabeta and gammadelta T cells influences the outcome of immune responses. Here we show that most gammadelta T lymphocytes expressed the tumor necrosis factor receptor family member CD27 and secreted interferon-gamma, whereas interleukin 17 production was restricted to CD27(-) gammadelta T cells. In contrast to the apparent plasticity of alphabeta T cells, the cytokine profiles of these distinct gammadelta T cell subsets were essentially stable, even during infection. These phenotypes were established during thymic development, when CD27 functions as a regulator of the differentiation of gammadelta T cells at least in part by inducing expression of the lymphotoxin-beta receptor and genes associated with trans-conditioning and interferon-gamma production. Thus, the cytokine profiles of peripheral gammadelta T cells are predetermined mainly by a mechanism involving CD27.
TL;DR: The data show that lymphoid tissue–inducer cells and natural killer cells shared unanticipated similarities and emphasize the heterogeneity of NKp46+CD3− cells in innate immunity, lymphoid organization and local tissue repair.
Abstract: NKp46+CD3- natural killer lymphocytes isolated from blood, lymphoid organs, lung, liver and uterus can produce granule-dependent cytotoxicity and interferon-gamma. Here we identify in dermis, gut lamina propria and cryptopatches distinct populations of NKp46+CD3- cells with a diminished capacity to degranulate and produce interferon-gamma. In the gut, expression of the transcription factor RORgammat, which is involved in the development of lymphoid tissue-inducer cells, defined a previously unknown subset of NKp46+CD3- lymphocytes. Unlike RORgammat- lamina propria and dermis natural killer cells, gut RORgammat+NKp46+ cells produced interleukin 22. Our data show that lymphoid tissue-inducer cells and natural killer cells shared unanticipated similarities and emphasize the heterogeneity of NKp46+CD3- cells in innate immunity, lymphoid organization and local tissue repair.
TL;DR: It is suggested that major histocompatibility complex class II–dependent interactions between basophils and CD4+ T cells promote T helper type 2 cytokine responses and immunity to helminth infection.
Abstract: Dendritic cells can prime naive CD4+ T cells; however, here we demonstrate that dendritic cell-mediated priming was insufficient for the development of T helper type 2 cell-dependent immunity. We identify basophils as a dominant cell population that coexpressed major histocompatibility complex class II and interleukin 4 message after helminth infection. Basophilia was promoted by thymic stromal lymphopoietin, and depletion of basophils impaired immunity to helminth infection. Basophils promoted antigen-specific CD4+ T cell proliferation and interleukin 4 production in vitro, and transfer of basophils augmented the population expansion of helminth-responsive CD4+ T cells in vivo. Collectively, our studies suggest that major histocompatibility complex class II-dependent interactions between basophils and CD4+ T cells promote T helper type 2 cytokine responses and immunity to helminth infection.