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T cells classically express either αβ or γδ T cell receptors. We have identified T cells that express both pairs of receptors. These hybrid αβ-γδ T cells exhibit a hyperinflammatory and migratory phenotype and act as first responders in infection and CNS autoimmunity., T cells are classically recognized as distinct subsets that express αβ or γδ TCRs. We identify a novel population of T cells that coexpress αβ and γδ TCRs in mice and humans. These hybrid αβ-γδ T cells arose in the murine fetal thymus by day 16 of ontogeny, underwent αβ TCR–mediated positive selection into CD4+ or CD8+ thymocytes, and constituted up to 10% of TCRδ+ cells in lymphoid organs. They expressed high levels of IL-1R1 and IL-23R and secreted IFN-γ, IL-17, and GM-CSF in response to canonically restricted peptide antigens or stimulation with IL-1β and IL-23. Hybrid αβ-γδ T cells were transcriptomically distinct from conventional γδ T cells and displayed a hyperinflammatory phenotype enriched for chemokine receptors and homing molecules that facilitate migration to sites of inflammation. These proinflammatory T cells promoted bacterial clearance after infection with Staphylococcus aureus and, by licensing encephalitogenic Th17 cells, played a key role in the development of autoimmune disease in the central nervous system., Graphical Abstract

The transcription factor BMAL1 is a core component of the molecular clock, regulating biological pathways that drive 24 h (circadian) rhythms in behaviour and physiology. The molecular clock has a profound influence on innate immune function, and circadian disruption is linked with increased incidence of multiple sclerosis (MS). However, the mechanisms underlying this association are unknown. Here we show that BMAL1 and time-of-day regulate the accumulation and activation of various immune cells in a CNS autoimmune disease model, experimental autoimmune encephalomyelitis (EAE). In myeloid cells, BMAL1 maintains anti-inflammatory responses and reduces T cell polarization. Loss of myeloid BMAL1 or midday immunizations to induce EAE create an inflammatory environment in the CNS through expansion and infiltration of IL-1β-secreting CD11b+Ly6Chi monocytes, resulting in increased pathogenic IL-17+/IFN-γ+ T cells. These findings demonstrate the importance of the molecular clock in modulating innate and adaptive immune crosstalk under autoimmune conditions., Circadian controls of immune responses by the molecular clock have been reported, but the underlying mechanisms are unclear. Here the authors show that the master circadian gene, Bmal1, is essential for modulating the homeostasis of myeloid cells to control pro-inflammatory IL-17+/IFN-γ+ T cells in autoimmunity.

Interleukin-17A (IL-17A) is a major mediator of tissue inflammation in many autoimmune diseases. Anti-IL-17A is an effective treatment for psoriasis and is showing promise in clinical trials in multiple sclerosis. In this study, we find that IL-17A-defective mice or mice treated with anti-IL-17A at induction of experimental autoimmune encephalomyelitis (EAE) are resistant to disease and have defective priming of IL-17-secreting γδ T (γδT17) cells and Th17 cells. However, T cells from Il17a-/- mice induce EAE in wild-type mice following in vitro culture with autoantigen, IL-1β, and IL-23. Furthermore, treatment with IL-1β or IL-17A at induction of EAE restores disease in Il17a-/- mice. Importantly, mobilization of IL-1β-producing neutrophils and inflammatory monocytes and activation of γδT17 cells is reduced in Il17a-/- mice. Our findings demonstrate that a key function of IL-17A in central nervous system (CNS) autoimmunity is to recruit IL-1β-secreting myeloid cells that prime pathogenic γδT17 and Th17 cells.

Retinoic acid attenuates colitis and is associated with increased IL-22 production from γδ T cells and innate lymphoid cells and enhanced antimicrobial peptide expression., Retinoic acid (RA), a vitamin A metabolite, modulates mucosal T helper cell responses. Here we examined the role of RA in regulating IL-22 production by γδ T cells and innate lymphoid cells in intestinal inflammation. RA significantly enhanced IL-22 production by γδ T cells stimulated in vitro with IL-1β or IL-18 and IL-23. In vivo RA attenuated colon inflammation induced by dextran sodium sulfate treatment or Citrobacter rodentium infection. This was associated with a significant increase in IL-22 secretion by γδ T cells and innate lymphoid cells. In addition, RA treatment enhanced production of the IL-22–responsive antimicrobial peptides Reg3β and Reg3γ in the colon. The attenuating effects of RA on colitis were reversed by treatment with an anti–IL-22 neutralizing antibody, demonstrating that RA mediates protection by enhancing IL-22 production. To define the molecular events involved, we used chromatin immunoprecipitation assays and found that RA promoted binding of RA receptor to the IL-22 promoter in γδ T cells. Our findings provide novel insights into the molecular events controlling IL-22 transcription and suggest that one key outcome of RA signaling may be to shape early intestinal immune responses by promoting IL-22 synthesis by γδ T cells and innate lymphoid cells.

The inflammatory cytokine IL-17 plays a critical role in immunity to infection and is involved in the inflammatory pathology associated with certain autoimmune diseases, such as psoriasis and rheumatoid arthritis. While CD4(+) and CD8(+) T cells are important sources of this cytokine, recent evidence has suggested that γδ T cells and a number of families of innate lymphoid cells (ILCs) can secrete IL-17 and related cytokines. The production of IL-17 by γδ T cells appears to be largely independent of T-cell receptor activation and is promoted through cytokine signalling, in particular by IL-23 in combination with IL-1β or IL-18. Therefore IL-17-secreting γδ T cells can be categorised as a family of cells similar to innate-like lymphoid cells. IL-17-secreting γδ T cells function as a part of mucosal defence against infection, with most studies to date focusing on their response to bacterial pathogens. γδ T cells also play a pathological role in certain autoimmune diseases, where they provide an early source of IL-17 and IL-21, which initiate responses mediated by conventional IL-17-secreting CD4(+) T cells (Th17 cells). ILCs lack an antigen receptor or other lineage markers, and ILC subsets that express the transcriptional factor RORγt have been found to secrete IL-17. Evidence is emerging that these newly recognised sources of IL-17 play both pathological and protective roles in inflammatory diseases as discussed in this article.

IL-1β plays a critical role in promoting IL-17 production by γδ and CD4 T cells. However, IL-1–targeted drugs, although effective against autoinflammatory diseases, are less effective against autoimmune diseases. Conversely, gain-of-function mutations in the NLRP3 inflammasome complex are associated with enhanced IL-1β and IL-18 production and Th17 responses. In this study, we examined the role of caspase-1–processed cytokines in IL-17 production and in induction of experimental autoimmune encephalomyelitis (EAE). Killed Mycobacterium tuberculosis, the immunostimulatory component in CFA used for inducing EAE, stimulated IL-1β and IL-18 production by dendritic cells through activation of the inflammasome complex and caspase-1. Dendritic cells stimulated with M. tuberculosis and myelin oligodendrocyte glycoprotein promoted IL-17 production by T cells and induced EAE following transfer to naive mice, and this was suppressed by a caspase-1 inhibitor and reversed by administration of IL-1β or IL-18. Direct injection of the caspase-1 inhibitor suppressed IL-17 production by CD4 T cells and γδ T cells in vivo and attenuated the clinical signs of EAE. γδ T cells expressed high levels of IL-18R and the combination of IL-18 and IL-23, as with IL-1β and IL-23, stimulated IL-17 production by γδ T cells, but also from CD4 T cells, in the absence of TCR engagement. Our findings demonstrate that caspase-1–processed cytokines IL-1β and IL-18 not only promote autoimmunity by stimulating innate IL-17 production by T cells but also reveal redundancy in the functions of IL-1β and IL-18, suggesting that caspase-1 or the inflammasome may be an important drug target for autoimmune diseases.

Inflammasome-mediated IL-1β production is central to the innate immune defects that give rise to certain autoinflammatory diseases and may also be associated with the generation of IL-17–producing CD4+ T (Th17) cells that mediate autoimmunity. However, the role of the inflammasome in driving adaptive immunity to infection has not been addressed. In this article, we demonstrate that inflammasome-mediated IL-1β plays a critical role in promoting Ag-specific Th17 cells and in generating protective immunity against Bordetella pertussis infection. Using a murine respiratory challenge model, we demonstrated that the course of B. pertussis infection was significantly exacerbated in IL-1R type I-defective (IL-1RI−/−) mice. We found that adenylate cyclase toxin (CyaA), a key virulence factor secreted by B. pertussis, induced robust IL-1β production by dendritic cells through activation of caspase-1 and the NALP3-containing inflammasome complex. Using mutant toxins, we demonstrate that CyaA-mediated activation of caspase-1 was not dependent on adenylate cyclase enzyme activity but was dependent on the pore-forming capacity of CyaA. In addition, CyaA promoted the induction of Ag-specific Th17 cells in wild-type but not IL-1RI−/− mice. Furthermore, the bacterial load was enhanced in IL-17–defective mice. Our findings demonstrate that CyaA, a virulence factor from B. pertussis, promotes innate IL-1β production via activation of the NALP3 inflammasome and, thereby, polarizes T cell responses toward the Th17 subtype. In addition to its known role in subverting host immunity, our findings suggest that CyaA can promote IL-1β–mediated Th17 cells, which promote clearance of the bacteria from the respiratory tract.

PUBLISHED, PMID: 19570828, IL-17 producing CD4+ T (Th17) cells are pathogenic in many autoimmune diseases. The induction and expansion of Th17 cells is directed by cytokines, including IL-23 and IL-1?, produced by innate immune cells through activation of pathogen recognition receptors (PRRs). The NF?B and interferon regulatory factor (IRF) families of transcriptional factors mediate IL-12 production; however, distinct signalling pathways appear to be required for IL- 23 production. Here we show that inhibition of ERK MAP kinase suppressed IL-23 and IL-1? production by dendritic cells (DC) stimulated with TLR or dectin-1 agonists, but did not affect IL-12p70 production. Furthermore, an ERK inhibitor suppressed the ability of antigen-pulsed TLR-activated DC to induce antigen-specific Th17 cells in vivo, but interestingly also inhibited the induction of Th1 cells. Treatment with an ERK inhibitor attenuated experimental autoimmune encephalomyelitis (EAE), when administered either at the induction phase of acute EAE or during remission in the relapsing-remitting EAE model. This was associated with significant suppression of autoantigen-specific Th17 and Th1 responses. The suppressive effect of the ERK inhibitor on attenuation of EAE was reversed by administration of IL-1? and IL-23. Our findings suggest that ERK MAP kinase plays a critical and hitherto undescribed role in activating innate production of IL-23 and IL-1?, which promote pathogenic T cell responses, and therefore represents an important target for therapeutic intervention against autoimmune diseases., This work was supported by Science Foundation Ireland.

Th17 cells, CD4(+) T cells that secrete interleukin-17 (IL-17), are pathogenic in autoimmune diseases and their development and expansion is driven by the cytokines IL-6, TGF-beta, IL-21, IL-1, and IL-23. However, there are also innate sources of IL-17. Here, we show that gammadelta T cells express IL-23R and the transcription factor RORgammat and produce IL-17, IL-21, and IL-22 in response to IL-1beta and IL-23, without T cell receptor engagement. IL-17-producing gammadelta T cells were found at high frequency in the brain of mice with experimental autoimmune encephalomyelitis (EAE). gammadelta T cells activated by IL-1beta and IL-23 promoted IL-17 production by CD4(+) T cells and increased susceptibility to EAE, suggesting that gammadelta T cells act in an amplification loop for IL-17 production by Th17 cells. Our findings demonstrate that gammadelta T cells activated by IL-1beta and IL-23 are an important source of innate IL-17 and IL-21 and provide an alternative mechanism whereby IL-1 and IL-23 may mediate autoimmune inflammation.

Prophylactic immunization of mice with autologous tumor-derived heat shock proteins (Hsp) generates effective anti-tumor immunity. However, this approach is ineffective when used therapeutically, partly due to the immunosuppressive effects of the growing tumor. Here we sought to overcome this problem by therapeutic vaccination with dendritic cells (DC) pulsed with Hsp70 and a COX-2 inhibitor. We found that Hsp70 induces IL-6 and IL-10 production and suppressed expression of CD40 on DC. Incubation of DC with tumor-conditioned medium attenuated Hsp70-induced expression of CD80 and induced expression of COX-2. Inhibition of COX-2 partially reversed the stimulatory effect of Hsp70 on DC IL-6 and IL-10 production and enhanced expression of CD80 and MHC classes I and II. Therapeutic administration of DC pulsed in vitro with Hsp70 in the presence of a COX-2 inhibitor significantly reduced progression of B16 tumors in mice and significantly enhanced survival. This was associated with a reduction in the frequency of IL-10-producing CD4 + T cells and enhancement of IFN-γ-producing CD8 + T cells. Our findings provide a novel immunotherapeutic approach against cancer based on attenuation of COX-2-mediated immunosuppression using in vitro modulated DC.

PUBLISHED, It was recently demonstrated that interleukin (IL)-23?driven IL-17?producing (ThIL-17) T cells mediate inflammatory pathology in certain autoimmune diseases. We show that the induction of antigen-specific ThIL-17 cells, but not T helper (Th)1 or Th2 cells, by immunization with antigens and adjuvants is abrogated in IL-1 receptor type I?deficient (IL-1RI?/?) mice. Furthermore, the incidence of experimental autoimmune encephalomyelitis (EAE) was significantly lower in IL-1RI?/? compared with wild-type mice, and this correlated with a failure to induce autoantigen-specific ThIL-17 cells, whereas induction of Th1 and Th2 responses was not substantially different. However, EAE was induced in IL-1RI?/? mice by adoptive transfer of autoantigen-specific cells from wild-type mice with EAE. IL-23 alone did not induce IL-17 production by T cells from IL-1RI?/? mice, and IL-23?induced IL-17 production was substantially enhanced by IL-1? or IL-1?, even in the absence of T cell receptor stimulation. We demonstrate essential roles for phosphatidylinositol 3-kinase, nuclear factor ?B, and novel protein kinase C isoforms in IL-1? and IL-23?mediated IL-17 production. Tumor necrosis factor ? also synergized with IL-23 to enhance IL-17 production, and this was IL-1 dependent. Our findings demonstrate that IL-1 functions upstream of IL-17 to promote pathogenic ThIL-17 cells in EAE., This work was supported by a Science Foundation Ireland Principal Investigator Award (no. 00/PI.I/B045 to K.H.G. Mills)

The NOD-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome is a component of the inflammatory process, and its aberrant activation is pathogenic in inherited disorders such as cryopyrin-associated periodic syndrome (CAPS) and complex diseases such as multiple sclerosis, type 2 diabetes, Alzheimer's disease and atherosclerosis. We describe the development of MCC950, a potent, selective, small-molecule inhibitor of NLRP3. MCC950 blocked canonical and noncanonical NLRP3 activation at nanomolar concentrations. MCC950 specifically inhibited activation of NLRP3 but not the AIM2, NLRC4 or NLRP1 inflammasomes. MCC950 reduced interleukin-1β (IL-1β) production in vivo and attenuated the severity of experimental autoimmune encephalomyelitis (EAE), a disease model of multiple sclerosis. Furthermore, MCC950 treatment rescued neonatal lethality in a mouse model of CAPS and was active in ex vivo samples from individuals with Muckle-Wells syndrome. MCC950 is thus a potential therapeutic for NLRP3-associated syndromes, including autoinflammatory and autoimmune diseases, and a tool for further study of the NLRP3 inflammasome in human health and disease.

Bordetella pertussis causes whooping cough, a severe and often lethal respiratory infection in infants. A recent resurgence of pertussis has been linked with waning or suboptimal immunity induced with acellular pertussis vaccines (Pa) that were introduced to most developed countries in the 1990s because of safety concerns around the use of whole-cell pertussis vaccines (Pw). Pa are composed of individual B. pertussis antigens absorbed to alum and promote strong antibody, T helper type 2 (Th2) and Th17 responses, but are less effective at inducing cellular immunity mediated by Th1 cells. In contrast, Pw, which include endogenous Toll-like receptor (TLR) agonists, induce Th1 as well as Th17 responses. Here we report the identification and characterization of novel TLR2-activating lipoproteins from B. pertussis. These proteins contain a characteristic N-terminal signal peptide that is unique to Gram-negative bacteria and we demonstrate that one of these lipoproteins, BP1569, activates murine dendritic cells and macrophages and human mononuclear cells via TLR2. Furthermore, we demonstrated that a corresponding synthetic lipopeptide LP1569 has potent immunostimulatory and adjuvant properties, capable of enhancing Th1, Th17, and IgG2a antibody responses induced in mice with an experimental Pa that conferred superior protection against B. pertussis infection than an equivalent vaccine formulated with alum.

Interleukin 17A-secreting T-helper 17 (Th17) cells are pathogenic in inflammatory kidney diseases, but their intrarenal regulation is poorly understood. In order to better define Th17 cell dynamics during interstitial inflammation, we utilized the mouse unilateral ureteral obstruction model to analyze inflammatory cell subtypes by multicolor flow cytometry and cell sorting and by effects on in vitro-generated Th17 cells. Interleukin 17A expression localized to CCR6(+)CCR4(+/-)CD4(+) T-cells and progressively increased in obstructed kidneys. The number of CCR6(+)CD4(+) T-cells increased over 10-fold by 72h, were enriched for interleukin 17A production, and were highly proliferative based on in vivo bromodeoxyuridine incorporation. Secreted products of leukocytes isolated from obstructed kidneys enhanced the interleukin 17A production of in vitro-generated Th17 cells. This Th17-enhancing activity was identified as interleukin-1 produced by renal dendritic cells and monocytes. The in vivo validity of these findings was confirmed in mice lacking the interleulin-1 receptor and in mice treated with a recombinant interleukin-1 receptor antagonist, each of which exhibited reduced intrarenal Th17 activity compared with control mice. Thus, the inflamed kidney accumulates CCR6(+) Th17 cells that undergo activation and proliferation. Production of interleukin 1 family cytokines by resident dendritic cells and infiltrating monocytes enhances intrarenal Th17 activation in acute kidney injury. Kidney International (2012) 81, 379-390; doi:10.1038/ki.2011.348; published online 5 October 2011

CD4+ T cells that secrete IL-17 (TH17 cells) play a key role in the pathogenesis of many auto-immune diseases and function with TH1 cells to mediate protective immunity to pathogens. The differentiation and expansion of TH17 cells from naive T cells appears to involve signals from IL-6, IL-1 IL-21, and IL-23. The role of TGF-β is more controversial with evidence that it can promote differentiation but also inhibit activation of TH17 cells. Although much of the focus has been on CD4+ T cells, and more recently CD8+ T cells, there is increasing evidence that innate cells, especially γδ T cells, but also NKT cells, are important sources of IL-17 and other TH17 associated cytokines. We have found that IL-1α or IL-1β can synergize with IL-23 to promote IL-17 secretion from memory T cells, and that IL-1β and IL-23, produced by dendritic cells in response to Toll-like receptor and NOD-like receptor activation, can also promote IL-17 production by γδ T cells without T cell receptor engagement. IL-17-producing γδ T cells are found at high frequency in the brain and spinal cord of mice with experimental auto-immune encephalomyelitis, where they function with TH17 cells to mediate auto-immune inflammation and pathology. γδ T cells appear to act as an important source of innate IL-17 and IL-21, which act in an amplification loop early in the immune response to promote further IL-17 production by TH17 cells. This chapter discusses the role of IL-1 and IL-23 in promoting IL-17 production by antigen-specific TH17 cells and innate IL-17 from γδ T cells and the role of IL-17-producing γδ T cells in auto-immunity and infection.

V γ 4+ T cells have been identified as the main IL-17-producing γ δ T cell in the CNS of mice with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. The findings of this study demonstrate that V γ 4+ T cells are present in T cell receptor (TCR) δ - / - mice, and furthermore these V γ 4+ T cells co-express TCR β . The data reveals that V γ 4 β T cells respond to IL-1 β and IL-23 stimulation in the absence of TCR engagement to produce IL-17A and IL-17F and express the master transcription factor, ROR γ t and the integrin, MCAM. Furthermore, V γ 4 β + T cells, together with conventional V γ 4 δ + T cells were found in the brains of mice with EAE. V γ 4 β + T cells were also found in the brains TCR δ - / - mice with EAE. Although, the course of EAE is somewhat reduced in TCR δ - / - compared with wild type (WT) mice, depletion of V γ 4+ T cells from TCR δ - / - as well as WT mice significantly attenuated clinical disease and weight loss in mice with EAE. Anti-V γ 4 treated mice with EAE had a significantly reduced frequency of infiltrating IL-17+, IFN- γ + and IFN- γ + IL-17+ CD4+ T cells into CNS. Furthermore, in the adoptive transfer model of EAE, depletion of V γ 4+ cells from lymph node and spleen cells from TCR δ - / - mice significantly impair their ability to induce EAE, with a reduction in inflammatory T cells infiltrating the CNS. Our study has identified a novel γ β T cell subset, V γ 4 β T cells, which together with conventional V γ 4 δ T cells, play a critical role in the pathogenesis of EAE through innate IL-17 production, necessary to enhance Th17 and Th1 activation and migration into the CNS to mediate inflammation and autoimmunity.

Reports describing the effect of interferon-gamma (IFNgamma) on interleukin-1beta (IL-1beta) production are conflicting. We resolve this controversy by showing that IFNgamma potentiates IL-1beta release from human cells, but transiently inhibits the production of IL-1beta from mouse cells. Release from this inhibition is dependent on suppressor of cytokine signalling 1. IL-1beta and Th17 cells are pathogenic in mouse models for autoimmune disease, which use Mycobacterium tuberculosis (MTB), in which IFNgamma and IFNbeta are anti-inflammatory. We observed that these cytokines suppress IL-1beta production in response to MTB, resulting in a reduced number of IL-17-producing cells. In human cells, IFNgamma increased IL-1beta production, and this might explain why IFNgamma is detrimental for multiple sclerosis. In mice, IFNgamma decreased IL-1beta and subsequently IL-17, indicating that the adaptive immune response can provide a systemic, but transient, signal to limit inflammation.

CD4+T cells that secrete IL-17 (Th17 cells) play a pathogenic role in many autoimmune diseases, but also function with Th1 cells to mediate protective immunity to infection by promoting recruitment and activation of neutrophils and macrophages respectively. Stimulation of dendritic cells by pathogen-derived molecules promotes maturation and the production of T-cell differentiating cytokines. We have shown that TLR and NLR agonists induce innate IL-1 and IL-18 which synergize with IL-23 to activate memory Th17 cells, but also IL-17 production by γδ T cells without TCR engagement. TLR signalling also leads to IL-12 production, which promotes induction of Th1 cells. Consequently TLR agonists are effective adjuvants for vaccines against infectious disease. We have demonstrated that TLR2 or TLR9 agonists are potent adjuvants for an acellular pertussis vaccine (aP) and considerably enhance its efficacy over the currently licensed aP which is administered with alum as the adjuvant. Whooping cough is a re-emerging infectious disease and the current aP induces Th2 and Th17 responses, but weak Th1 responses. Interestingly, Th2 responses were redundant and protection with alum-adjuvanted aP is mediated by Th17 cells, driven by alum-activated IL-1β. In contrast, immunization with an aP formulation containing a novel TLR2 lipopeptide from Bordetella pertussis or a TLR9 agonist induced strong Th1 and IgG2a responses and a high level of protection against respiratory infection with Bordetella pertussis. In the field of autoimmunity, much of the focus in drug discovery has been on IL-17A production by CD4+ Th17 cells and its induction by IL-23. However CD8+ T cells, gd T cells, NKT cells and other innate lymphoid cells are all capable of secreting IL-17A. There is also evidence that other cytokines, including IL-17F, GM-CSF, IL-21 and IL-22, are produced by Th17 and IL-17A-secreting innate immune cells. Furthermore, the role of IFN-γ, secreted by Th1, NK and type 1 innate lymphoid cells (ILC1) cells, is still unclear, with some evidence that IFN-γ is protective in autoimmunity by inhibiting Th17 cells. However, we have demonstrated in experimental autoimmune encephalomyelitis, a mouse model for multiple sclerosis, that early NK cell-derived IFN-γ plays a pathogenic role through activation of M1 macrophages and VLA4 expression on T cells, required for their migration into the CNS. The induction and function of Th1 and Th17 cells is regulated by cytokines secreted by the other major subtypes of T cells, especially IL-10 and TGF-β production by Treg cells but also by regulatory cells of the innate immune system. The induction of adaptive Treg cells is stimulated by retinoic acid, TGF-β and IL-10 in response to certain virulence factors from pathogens, such as helminth parasites that have evolved sophisticated mechanisms to subvert host protective immunity. Pathogens and pathogen-derived molecules can also promote activation of alternatively activated M2 macrophages, ILC2 and tolerogenic dendritic cells that can suppress Th1 or Th17 cells, either directly or through the induction of Treg cells. We have identified approaches for activation of anti-inflammatory cytokines, regulatory innate immune cells and Treg cells, without Th1 or Th17 cells. These approaches have been effective in attenuating inflammatory disease in pre-clinical models of autoimmunity.

NLRP3 is a critical component of the inflammatory process and its aberrant activation is pathogenic in inherited disorders such as the cryopyrin associated periodic syndromes and complex diseases such as multiple sclerosis, type II diabetes and atherosclerosis. There is a compelling rationale to develop a potent, selective inhibitor of NLRP3. We demonstrate that a small molecule, MCC950, specifically blocks NLRP3 activation at nanomolar potency in response to numerous stimuli. MCC950 potently inhibits ASC oligomerisation, caspase-1 activation, IL-1 β secretion and cell death in response to NLRP3 but not AIM2, NLRC4 or NLRP1 inflammasome activation. MCC950 can block IL-1b in vivo and attenuates the course of the NLRP3 dependent, IL-1b driven disease model of multiple sclerosis, experimental autoimmune encephalomyelitis. Furthermore, MCC950 treatment rescues neonatal lethality in a murine model of cryopyrin associated periodic syndromes and is active in ex vivo samples from patients with Muckle–Wells syndrome. MCC950 is thus a novel potential therapeutic for NLRP3 associated syndromes and a useful tool for the further study of NLRP3 in human health and disease.

Whooping cough caused by Bordetella pertussis is a re-emerging infectious disease despite the introduction of safer acellular pertussis vaccines (Pa). One explanation for this is that Pa are less protective than the more reactogenic whole cell pertussis vaccines (Pw) that they replaced. Although Pa induce potent antibody responses, and protection has been found to be associated with high concentrations of circulating IgG against vaccine antigens, it has not been firmly established that host protection induced with this vaccine is mediated solely by humoral immunity. The aim of this study was to examine the relative contribution of Th1 and Th17 cells in host immunity to infection with B. pertussis and in immunity induced by immunization with Pw and Pa and to use this information to help rationally design a more effective Pa. Our findings demonstrate that Th1 and Th17 both function in protective immunity induced by infection with B. pertussis or immunization with Pw. In contrast, a current licensed Pa, administered with alum as the adjuvant, induced Th2 and Th17 cells, but weak Th1 responses. We found that IL-1 signalling played a central role in protective immunity induced with alum-adsorbed Pa and this was associated with the induction of Th17 cells. Pa generated strong antibody and Th2 responses, but was fully protective in IL-4-defective mice, suggesting that Th2 cells were dispensable. In contrast, Pa failed to confer protective immunity in IL-17A-defective mice. Bacterial clearance mediated by Pa-induced Th17 cells was associated with cell recruitment to the lungs after challenge. Finally, protective immunity induced by an experimental Pa could be enhanced by substituting alum with a TLR agonist that induces Th1 cells. Our findings demonstrate that alum promotes protective immunity through IL-1β-induced IL-17A production, but also reveal that optimum protection against B. pertussis requires induction of Th1, but not Th2 cells., Author Summary The bacterium Bordetella pertussis causes whooping cough, a severe and often lethal respiratory infection in humans. The disease was largely controlled through vaccination with whole cell pertussis vaccines (Pw). However, Pw had side effects and were replaced in developed countries in the 1990s with safer acellular pertussis vaccines (Pa). Unfortunately this has now been linked with a recent resurgence of whooping cough. We have used a mouse model to examine the mechanism of host immunity against B. pertussis. We examined the type of immune responses induced with Pa compared with Pw in an attempt to identify its shortcomings and to design a more effective vaccine. Traditionally it had been considered that antibodies mediate protection induced with pertussis vaccines. However, we found that blood lymphocytes, in particular a subpopulation of T cells called Th17 cells that secrete a cytokine called IL-17, play a critical role in host immunity induced by Pa. In contrast, Pw induce Th17 cells but also another T cell subtype called Th1 cells, which are also required for optimum immunity. Finally, we rationally designed a new vaccine using a formulation that induces Th1 cells and found that this was highly effective in conferring protective immunity.

We are pleased to read that our paper (Sutton et al., 2009), as well as that of Martin et al. (2009), has stimulated a debate on the importance of γδ T cells in interleukin-17 (IL-17) production and the signals that may drive this production. We acknowledge the contribution that O'Brien and colleagues have made to our understanding of the role of IL-17 production by γδ T cells in autoimmunity in our manuscript. However, we do not agree with their assertion that we “claim priority” or that we did not acknowledge previous contributions to the discovery that “γδ T cells can produce IL-17 without deliberate stimulation via the T cell receptor.” Indeed we cited the contribution by Shibata et al.