A healthy immune system's core challenge is to mount appropriate responses to an immense and unknown variety of antigenic stimuli. By unraveling the regulatory networks that drive and control immune-cell behaviors, we can begin to identify the means by which proper balance can be achieved and aberrant behaviors clinically corrected. Traditionally, major advances in our understanding of cellular immunological processes depended critically on both improved perturbation and enhanced observation methods. In my doctoral research, I have pursued both strategies to elucidate the differentiation and effector functions of adaptive immune Th17 cells. These cells exemplify the need for balance: while Th17 cells are needed to induce clearance of fungal infections and extracellular bacteria, irregular responses have been strongly implicated in autoimmunity. / Chemistry and Chemical Biology

The interleukin (IL)-12 family of cytokines plays a key role in the orchestration of cellular immune responses, bridging innate and adaptive immunity. The founding member, IL-12, was discovered in the late 1980s as the first heterodimeric cytokine, composed of a 40 kDa (p40) and 35 kDa (p35) subunit. Years of basic and clinical research on this prototypical T helper type (Th)1 cytokine revealed its importance in immunity to intracellular non-viral infections, as well as in cancer and autoimmune diseases. Since the discovery of IL-23 as another cytokine composed of the p40 subunit of IL-12 in the year 2000, IL-23, rather than IL-12, could be shown to be the key player in rodent models of autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. With accumulating evidence revealing IL-23 as the crucial regulator of a non-classical pathway of cellular immunity which is hallmarked by IL-17 producing T cells it is intriguing to gain understanding of the importance of such findings in immunity to infections. The present work describes a series of in vivo studies investigating the role of endogenous as well as exogenous IL-23 in a murine model of chronic fungal infection, cryptococcosis. To address the role of endogenous IL-23, wild-type (WT), IL-12- (IL-12p35-/-), IL-23- (IL-23p19-/-) deficient, as well as IL-12- and IL-23- double deficient (p40-deficient) mice on a C57BL/6 background were infected with Cryptococcus neoformans (C. neoformans). Following infection, p40-deficient mice demonstrated higher mortality than IL-12p35-/- mice. Reconstitution of p40-deficient mice with recombinant murine IL-23 prolonged their survival to levels similar to IL-12p35-/- mice. IL-23p19-/- mice showed a moderately reduced survival time and delayed fungal clearance in the liver. While interferon (IFN)-γ production was similar in WT and IL-23p19-/- mice, production of IL-17 was strongly impaired in the latter. IL-23p19-/- mice produced fewer hepatic granulomata relative to organ burden and showed defective recruitment of mononuclear cells to the brain. Moreover, activation of microglia cells and expression of IL-1β, IL-6, and MCP-1 in the brain was impaired. SUMMARY - 80 - The second part of the present work explores the mechanisms underlying the IL-23 effects by characterizing the role of exogenous IL-23. C. neoformans-infected C57BL/6 WT mice treated with recombinant murine IL-23 showed significantly prolonged survival time as compared to mock-treated control mice. However, complete survival throughout the observation period (100 days) was only achieved following IL-12 treatment. At day 21 post infection (p.i.) the IL-23-treated mice as well as the IL-12 group had a significantly lower fungal burden in the brain than the control mice. However, while IL-12 treatment was associated with elevated serum levels of the proinflammatory mediators IFN-γ, tumor necrosis factor (TNF)-α and nitric oxide, IL-23-treated animals, although more resistant, developed a Th2 response similar to the control group as measured by serum IgE levels. Further experiments to assess the mechanism of action were based on the finding of reduced fungal burden at the site of infection, the peritoneal cavity, at day 8 p.i. following IL-23 treatment. This microbicidal effect was also seen in p40-deficient as well as in T and B cell deficient (RAG-deficient) mice. Administration of IL-23 led to enhanced recruitment of inflammatory cells, not only of T cells but also cells of the innate immune system such as DCs, natural killer cells and granulocytes to the infected site. Although numbers of macrophages were not altered following IL-23 treatment, co-stimulatory molecules were markedly up-regulated on such cells. The chemokine/cytokine pattern induced by IL-23 treatment was hallmarked by proinflammatory mediators such as MCP-1, IL-1β, IL-6, TNF-α and IL-17, but also the Th2 associated cytokine IL-5. From these results it can be concluded that a non-classical immune pathway induced by IL-23 complements the more dominant role of IL-12 in protection against C. neoformans. This novel immune response is characterized by an enhancement of the inflammatory cell response and the production of a proinflammatory cytokine pattern hallmarked by IL-1β, IL-6, TNF-α and IL-17.

OBJETIVO: Avaliar a expressão dos perfis de citocinas Th1, Th2 e Th17 em pacientes com LES e verificar possíveis associações com os níveis séricos de vitamina D. MÉTODOS: Estudo transversal com inclusão de 172 pacientes acompanhados no ambulatório de reumatologia do Hospital de Clínicas de Porto Alegre. Os níveis de vitamina D foram medidos por quimiluminescência. Níveis séricos <20 ng/ml foram considerados como deficiência de vitamina D e níveis ≥20 ng/ml foram considerados normais. As citocinas foram medidas no soro após o descongelamento das amostras em uma única ocasião, usando Kit CBA (cytometric beads array) Th1/Th2/Th17. RESULTADOS: Cento e sessenta e um (94%) pacientes eram mulheres e 128 (74,4%) foram classificados como euro-descendentes. A idade média foi de 40,5±13,8 anos e a idade média no momento do diagnóstico foi de 31,5±13,4 anos. Na entrada do estudo, os pacientes tiveram mediana (intervalo interquartil) de atividade da doença (SLEDAI- systemic lupus erythematosus disease activity index) de 2 (1-4) e cronicidade (SLICC damage index- systemic lupus international collaborating clinics) de 0 (0-1). O nível médio de vitamina D foi de 25,4±11,04 ng/ml. Cinquenta e nove (34,3%) pacientes apresentavam deficiência de vitamina D e 113 (65,7%) tinham níveis considerados normais. Nenhuma associação e correlação estatisticamente significativa foram encontradas. Os níveis de INF-α e SLEDAI mostraram uma correlação positiva fraca (rs=0,22, p=0,04). Análise de regressão linear foi realizada para controlar possíveis fatores de confusão. CONCLUSÃO: A deficiência de vitamina D é prevalente em pacientes com LES, entretanto, não foram encontradas correlações e associações entre níveis de vitamina D e perfil de citocinas. Confirmamos a correlação existente entre o IFN-α e SLEDAI, conforme a literatura. Efeito in vitro de vitamina D no perfil de citocinas não foi reproduzido no presente estudo. Estudos longitudinais podem ajudar a esclarecer a influência da vitamina D na fisiopatogenia do LES. / OBJECTIVES: To evaluate the expression of Th1, Th2 and Th17 cytokine profiles in SLE patients and verify possible associations with serum vitamin D levels. METHODS: Cross-sectional study with 172 SLE patients, followed at the outpatient clinic of rheumatology at Hospital de Clínicas de Porto Alegre were included. The levels of vitamin D were measured by chemiluminescence. Serum levels <20 ng/ml were considered as vitamin D deficiency. Normal vitamin D levels were defined as ≥20ng/ml. Cytokines were measured in serum after thawing the samples on a single occasion, using Kit CBA (cytometric beads array) Th1/Th2/Th17. RESULTS: One hundred sixty one (94%) patients were women and 128 (74.4%) were classified as European derived. The mean age of patients was 40.5±13.8 years and the mean age at diagnosis was 31.5±13.4 years. At the time of study entry, patients had median (IQR) of active disease (SLEDAI- systemic lupus erythematosus disease activity index) of 2 (1-4) and chronicity (SLICC damage index- systemic lupus international collaborating clinics) of 0 (0-1). Mean vitamin D levels were 25.4±11.04 ng/ml. Fifty-nine (34.3%) patients had vitamin D deficiency and 113 (65.7%) had normal levels. No association and statistically significant correlations was found. The levels of INF-α and SLEDAI showed a weak positive correlation (rs=0.22, p=0.04). Linear regression analysis was performed to control for possible confounding factors. CONCLUSION:Vitamin D deficiency is prevalent in patients with SLE, however, no statistically significant correlations and associations between vitamin D levels and cytokine profile were found. We confirm the correlation between IFN-α and SLEDAI, according to the literature. In vitro effect of vitamin D on the cytokine profile was not reproduced in this study. Longitudinal studies may help clarify the influence of vitamin D in the pathogenesis of SLE.

Les immunoglobulines circulantes jouent un rôle critique dans l’homéostasie immune en modulant les fonctions des cellules du système immunitaire. Au cours de ma thèse, j’ai exploré les effets régulateurs des immunoglobulines G thérapeutiques (IVIG) et des immunoglobulines A monomériques circulantes (mIgA) sur l’autophagie et les réponses Th17 respectivement. Les IVIg sont une préparation thérapeutique d’IgG normales poolées. Elles ont utilisées comme agent anti-inflammatoire dans le traitement de maladies auto-immunes et inflammatoires variées. Cependant, les mécanismes ne sont pas complètement élucidés et plusieurs mécanismes mutuels et non exclusifs ont été proposés. L’autophagie est un important processus biologique impliquant la dégradation lysosomale des composants cellulaires endommagés et des protéines mal repliées. Il y a plusieurs preuves montrant l’implication de l’autophagie dans les maladies auto-immunes et auto-inflammatoires incluant la découverte de polymorphismes dans des gènes liés à l’autophagie. J’ai montré que l’induction de l’autophagie par les IVIG représente un nouveau mécanisme d’action permettant leur effet thérapeutique dans les maladies auto-immunes et inflammatoires. Les Th17 représentent une cible attractive pour traiter plusieurs maladies inflammatoires et auto-immunes. Malgré le fait qu’elles sont le deuxième anticorps le plus abondant dans la circulation, la function immunorégulatrice des IgA n’est relativement pas explorée. J’ai montré que les IgA monomériques (mIgA) inhibent la différentiation et l’amplification des cellules Th17 humaines et la production de leur cytokine effectrice IL-17A. / Circulating immunoglobulins play a critical role in the immune homeostasis by modulating the functions of immune cells. In my thesis, I investigated the regulatory effects of therapeutic immunoglobulin G (IVIG) and circulating monomeric immunoglobulin A (mIgA) on autophagy and human Th17 response respectively. IVIG is a therapeutic preparation of pooled normal IgG. It is used as an anti-inflammatory agent in the treatment of a wide variety of autoimmune and inflammatory diseases. However, the mechanisms are not yet fully elucidated and several mutually non-exclusive mechanisms have been proposed. Autophagy is an important biological process involving lysosomal degradation of damaged cellular components and misfolded proteins. There are several evidences that support the involvement of autophagy in autoimmune and auto- inflammatory disorders including the discovery of polymorphisms in autophagy-related genes. I show that induction of autophagy by IVIG represents a novel mechanism of action in achieving therapeutic effect in autoimmune and inflammatory diseases. Th17 cells represent an attractive target to treat several inflammatory and autoimmune diseases. Despite being second most abundant antibody in the circulation, the immunoregulatory function of IgA is relatively unexplored. I have shown that monomeric IgA (mIgA) inhibits differentiation and amplification of human Th17 cells and the production of their effector cytokine IL-17A.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2012-09-04T18:17:28Z No. of bitstreams: 1 Wendell Vilas Boas Santos Metabolismo da arginina e moléculas....pdf: 3424976 bytes, checksum: 754d4fef738c69d02fff1ba7595f9dfc (MD5) / Made available in DSpace on 2012-09-04T18:17:28Z (GMT). No. of bitstreams: 1 Wendell Vilas Boas Santos Metabolismo da arginina e moléculas....pdf: 3424976 bytes, checksum: 754d4fef738c69d02fff1ba7595f9dfc (MD5) Previous issue date: 2011 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, Bahia, Brasil / A anemia falciforme (AF) é uma doença genética com prevalência mundial elevada, sendo considerada uma doença multisistêmica, uma vez que é caracterizada por manifestações clínicas agudas e crônicas e pelo comprometimento progressivo de órgãos e sistemas. A AF é caracterizada por uma disfunção endotelial acentuada que pode ser decorrente de vários fatores. Os distúrbios no metabolismo da arginina estão relacionados ao estado inflamatório crônico apresentado pelos pacientes com AF e a homocysteína (Hcy) pode também estar relacionada, cujo aumento plasmático está associado a ativação endotelial e o estado inflamatório em diferentes patologias. Estão inclusos nesta tese o conjunto de três manuscritos com o objetivo de investigar moléculas associadas à ativação endotelial em pacientes com AF, com ênfase para as moléculas envolvidas no metabolismo do óxido nítrico (NO), como a arginase; Hcy, citocinas Th17, moléculas de adesão solúveis (sVCAM-1 e sICAM-1) e marcadores hemolíticos. Foram estudados indivíduos com AF em estado estávelNossos resultados mostraram que a arginase plasmática e a citocina IL-17 estão elevada em pacientes com AF. Além disso, a citocina TGF-beta está positivamente associada a arginase nos mesmos pacientes. A Hcy foi associada com a ativação endotelial, uma vez que a Hcy esteve correlacionada positivamente com sVCAM e as citocinas IL-17 e TGF-beta. Os níveis diminuídos da citocina IL-18 foram relacionados a ocorrência de seqüestro esplênico. O papel de novos marcadores de inflamação vascular pode ajudar no entendimento da complexidade da fisiopatologia da AF, principalmente o relacionado ao metabolismo da arginina e NO, moléculas cruciais na manutenção vascular. Nossos dados mostram alvos importantes, como a arginase, Hcy e a IL17, que podem ser explorados como fatores adicionais na inflamação, ativação endotelial e vaso-oclusão na AF. / Sickle-cell disease is one of the most common severe monogenic disorders worldwide. It is consider a multisystem disease, associated with episodes of acute illness and progressive organ damage. Sickle Cell Anemia (SCA) is characterized by a marked endothelial dysfunction, owing to many factors. Dysregulated arginine metabolism can be related to the inflammatory chronic state presented by patients and homocysteine (Hcy) can be also related to inflammatory state, once its increase serum levels can enhance the endothelial activation and inflammation state in several pathologies. It was included in this thesis a set of three manuscripts that aim to investigate molecules implicated in the endothelial activation in SCA patients, emphasizing molecules involved on Nitric Oxide (NO) metabolism, such as arginase, Hcy, Th17, cytokines, soluble adhesion molecules (sVCAM-1 e sICAM-1) and hemolytic markers. We studied sickle cell anemia patients in stead state. Our results showed a rising arginase levels and IL-17 cytokine in the SCA patients. Moreover, the cytokine TGF-beta is associated with higher arginase levels in the same sickle cell patients. The Hcy was related to endothelial activation, since the Hcy was positively associated with sVCAM, IL-17 and TGF-beta. Patients who had a splenic sequestration event had low IL-18 levels. The role of novel inflammation markers can help to understand the complexity of pathofisiology in the SCA, mainly related to arginine and NO metabolism that is essential to vascular maintenance. Our data show important targets, such as arginase, Hcy and IL-17, that can be explored as an additional risk factor to endothelial inflammation and activation and vaso-occlusion in SCD.

OBJETIVO: Avaliar a expressão dos perfis de citocinas Th1, Th2 e Th17 em pacientes com LES e verificar possíveis associações com os níveis séricos de vitamina D. MÉTODOS: Estudo transversal com inclusão de 172 pacientes acompanhados no ambulatório de reumatologia do Hospital de Clínicas de Porto Alegre. Os níveis de vitamina D foram medidos por quimiluminescência. Níveis séricos <20 ng/ml foram considerados como deficiência de vitamina D e níveis ≥20 ng/ml foram considerados normais. As citocinas foram medidas no soro após o descongelamento das amostras em uma única ocasião, usando Kit CBA (cytometric beads array) Th1/Th2/Th17. RESULTADOS: Cento e sessenta e um (94%) pacientes eram mulheres e 128 (74,4%) foram classificados como euro-descendentes. A idade média foi de 40,5±13,8 anos e a idade média no momento do diagnóstico foi de 31,5±13,4 anos. Na entrada do estudo, os pacientes tiveram mediana (intervalo interquartil) de atividade da doença (SLEDAI- systemic lupus erythematosus disease activity index) de 2 (1-4) e cronicidade (SLICC damage index- systemic lupus international collaborating clinics) de 0 (0-1). O nível médio de vitamina D foi de 25,4±11,04 ng/ml. Cinquenta e nove (34,3%) pacientes apresentavam deficiência de vitamina D e 113 (65,7%) tinham níveis considerados normais. Nenhuma associação e correlação estatisticamente significativa foram encontradas. Os níveis de INF-α e SLEDAI mostraram uma correlação positiva fraca (rs=0,22, p=0,04). Análise de regressão linear foi realizada para controlar possíveis fatores de confusão. CONCLUSÃO: A deficiência de vitamina D é prevalente em pacientes com LES, entretanto, não foram encontradas correlações e associações entre níveis de vitamina D e perfil de citocinas. Confirmamos a correlação existente entre o IFN-α e SLEDAI, conforme a literatura. Efeito in vitro de vitamina D no perfil de citocinas não foi reproduzido no presente estudo. Estudos longitudinais podem ajudar a esclarecer a influência da vitamina D na fisiopatogenia do LES. / OBJECTIVES: To evaluate the expression of Th1, Th2 and Th17 cytokine profiles in SLE patients and verify possible associations with serum vitamin D levels. METHODS: Cross-sectional study with 172 SLE patients, followed at the outpatient clinic of rheumatology at Hospital de Clínicas de Porto Alegre were included. The levels of vitamin D were measured by chemiluminescence. Serum levels <20 ng/ml were considered as vitamin D deficiency. Normal vitamin D levels were defined as ≥20ng/ml. Cytokines were measured in serum after thawing the samples on a single occasion, using Kit CBA (cytometric beads array) Th1/Th2/Th17. RESULTS: One hundred sixty one (94%) patients were women and 128 (74.4%) were classified as European derived. The mean age of patients was 40.5±13.8 years and the mean age at diagnosis was 31.5±13.4 years. At the time of study entry, patients had median (IQR) of active disease (SLEDAI- systemic lupus erythematosus disease activity index) of 2 (1-4) and chronicity (SLICC damage index- systemic lupus international collaborating clinics) of 0 (0-1). Mean vitamin D levels were 25.4±11.04 ng/ml. Fifty-nine (34.3%) patients had vitamin D deficiency and 113 (65.7%) had normal levels. No association and statistically significant correlations was found. The levels of INF-α and SLEDAI showed a weak positive correlation (rs=0.22, p=0.04). Linear regression analysis was performed to control for possible confounding factors. CONCLUSION:Vitamin D deficiency is prevalent in patients with SLE, however, no statistically significant correlations and associations between vitamin D levels and cytokine profile were found. We confirm the correlation between IFN-α and SLEDAI, according to the literature. In vitro effect of vitamin D on the cytokine profile was not reproduced in this study. Longitudinal studies may help clarify the influence of vitamin D in the pathogenesis of SLE.

OBJETIVO: Avaliar a expressão dos perfis de citocinas Th1, Th2 e Th17 em pacientes com LES e verificar possíveis associações com os níveis séricos de vitamina D. MÉTODOS: Estudo transversal com inclusão de 172 pacientes acompanhados no ambulatório de reumatologia do Hospital de Clínicas de Porto Alegre. Os níveis de vitamina D foram medidos por quimiluminescência. Níveis séricos <20 ng/ml foram considerados como deficiência de vitamina D e níveis ≥20 ng/ml foram considerados normais. As citocinas foram medidas no soro após o descongelamento das amostras em uma única ocasião, usando Kit CBA (cytometric beads array) Th1/Th2/Th17. RESULTADOS: Cento e sessenta e um (94%) pacientes eram mulheres e 128 (74,4%) foram classificados como euro-descendentes. A idade média foi de 40,5±13,8 anos e a idade média no momento do diagnóstico foi de 31,5±13,4 anos. Na entrada do estudo, os pacientes tiveram mediana (intervalo interquartil) de atividade da doença (SLEDAI- systemic lupus erythematosus disease activity index) de 2 (1-4) e cronicidade (SLICC damage index- systemic lupus international collaborating clinics) de 0 (0-1). O nível médio de vitamina D foi de 25,4±11,04 ng/ml. Cinquenta e nove (34,3%) pacientes apresentavam deficiência de vitamina D e 113 (65,7%) tinham níveis considerados normais. Nenhuma associação e correlação estatisticamente significativa foram encontradas. Os níveis de INF-α e SLEDAI mostraram uma correlação positiva fraca (rs=0,22, p=0,04). Análise de regressão linear foi realizada para controlar possíveis fatores de confusão. CONCLUSÃO: A deficiência de vitamina D é prevalente em pacientes com LES, entretanto, não foram encontradas correlações e associações entre níveis de vitamina D e perfil de citocinas. Confirmamos a correlação existente entre o IFN-α e SLEDAI, conforme a literatura. Efeito in vitro de vitamina D no perfil de citocinas não foi reproduzido no presente estudo. Estudos longitudinais podem ajudar a esclarecer a influência da vitamina D na fisiopatogenia do LES. / OBJECTIVES: To evaluate the expression of Th1, Th2 and Th17 cytokine profiles in SLE patients and verify possible associations with serum vitamin D levels. METHODS: Cross-sectional study with 172 SLE patients, followed at the outpatient clinic of rheumatology at Hospital de Clínicas de Porto Alegre were included. The levels of vitamin D were measured by chemiluminescence. Serum levels <20 ng/ml were considered as vitamin D deficiency. Normal vitamin D levels were defined as ≥20ng/ml. Cytokines were measured in serum after thawing the samples on a single occasion, using Kit CBA (cytometric beads array) Th1/Th2/Th17. RESULTS: One hundred sixty one (94%) patients were women and 128 (74.4%) were classified as European derived. The mean age of patients was 40.5±13.8 years and the mean age at diagnosis was 31.5±13.4 years. At the time of study entry, patients had median (IQR) of active disease (SLEDAI- systemic lupus erythematosus disease activity index) of 2 (1-4) and chronicity (SLICC damage index- systemic lupus international collaborating clinics) of 0 (0-1). Mean vitamin D levels were 25.4±11.04 ng/ml. Fifty-nine (34.3%) patients had vitamin D deficiency and 113 (65.7%) had normal levels. No association and statistically significant correlations was found. The levels of INF-α and SLEDAI showed a weak positive correlation (rs=0.22, p=0.04). Linear regression analysis was performed to control for possible confounding factors. CONCLUSION:Vitamin D deficiency is prevalent in patients with SLE, however, no statistically significant correlations and associations between vitamin D levels and cytokine profile were found. We confirm the correlation between IFN-α and SLEDAI, according to the literature. In vitro effect of vitamin D on the cytokine profile was not reproduced in this study. Longitudinal studies may help clarify the influence of vitamin D in the pathogenesis of SLE.

L'inflammasome est complexe protéique intracellulaire de l'immunité innée permettant la reconnaissance de pathogènes intracellulaires. NLRC4, un Nod-like récepteur permettant l'activation de l'inflammasome est impliqué dans la reconnaissance du flagelle ainsi que du système de sécrétion de type 3 (SST3) de Pseudomonas aeruginosa, une bactérie majoritairement extracellulaire. Nous avons donc déterminer l'impact de la reconnaissance de P. aeruginosa par le NLRC4-inflammasome in vivo dans un modèle murin de pneumonie aiguë. De façon surprenante, l'activation du NLRC4-inflammasome par le SST3 de P. aeruginosa contribue à diminuer la survie de l'hôte en diminuant la clairance bactérienne pulmonaire et en augmentant la lésion pulmonaire induite. En effet, la perte de l'activation de l'inflammasome chez les souris NLRC4/- permet d'une part, une réponse précoce méfiée par l'IL-17A. Cette réponse dépendant de l'IL-17A conduit à une expression majeure de peptides antimicrobiens par l'épithélium pulmonaire et diminue la lésion pulmonaire en diminuant le recrutement des cellules immunitaires inflammatoires. L'administration d'IL-18 recombinante murine ou l'inhibition de cette voie par un anticorps anti-IL-17A inhibe cette réponse IL-17A dépendante. Ces résultats mettent en évidence un nouveau rôle du SST3 de P. aeruginosa, qui en plus de son effet cytotoxique et de la translocation d'exotoxines, permet d'activer l'inflammasome pour échapper à la réponse immunitaire innée de l'hôte en inhibant une voie IL-17 dépendante. / The inflammasome is thought to function as a cytosolic surveillance system against intracellular pathogens. However, we report that Pseudomonas aeruginosa, an extracellular pathogen responsible for acute lung infection, relies upon inflammasome activation to persist and worsen disease. Specifically, we show that loss of either NLRC4 expression or type-3 secretion system (T3SS)-driven activation of NLRC4, surprisingly, resulted in a robust Th-17-like immune response that enhanced bacterial clearance and attenuated virulence independently of exotoxins. This Th-17-like response correlated with marked upregulation of antimicrobial peptides and was suppressed by either neutralization of IL-17A or exogenous IL-18 administration in vivo. Together, these results unveil an adaptation mechanism through which the problem pathogen manages to evade Th17-mediated immunity and invade the lung, providing a potential mechanism for infectious complications of anti-IL17 therapy in inflammatory diseases. The T3SS exploitation of NLRC4-coupled inflammasome response may therefore represent a novel gene-for-gene model of pathogen evolution alongside host immunity.

Background: Age is an important risk factor for rheumatoid arthritis (RA), which often develops in middle age. However, how age-associated changes in immunity impact RA is poorly understood. Gut microbiota are known to be involved in the pathogenesis of RA, but the effects of microbiota in older subjects remain mostly unknown. Methods: We used segmented filamentous bacteria (SFB), a gut commensal species with immunomodulatory effects, and K/BxN mice, a T cell receptor (TCR) transgenic model, to study the effect of age and microbiota on autoimmune arthritis. Comparing young and middle-aged K/BxN T cells of the same TCR specificity allows us to study T cells with an age focus eliminating a key variable: TCR repertoire alteration with age. In addition to joints, we also studied pathological changes in the lung, an important extra-articular RA manifestation. We used flow cytometry to evaluate T follicular helper (Tfh) and T helper 17 (Th17) cells, as they both contribute to autoantibody production, a key disease index in both RA and K/BxN arthritis. Results: Middle-aged K/BxN mice had aggravated arthritis and pathological changes in the lung compared to young mice. Middle-aged mice displayed a strong accumulation of Tfh but not Th17 cells, and had defective Th17 differentiation and low expression of interleukin-23, a critical cytokine for Th17 maintenance. Although a soaring Tfh cell population accompanied by robust germinal center B cell responses were found in middle-aged mice, there was decreased cycling of Tfh cells, and SFB only induced the non-Tfh cells to upregulate Bcl-6, the Tfh master transcription factor, in the young but not the middle-aged group. Finally, the accumulated Tfh cells in middle-aged mice had an effector phenotype (CD62LloCD44hi). Conclusion: Age-dependent Tfh cell accumulation may play a crucial role in the increased autoimmune disease phenotype in middle-age. SFB, a potent stimulus for inducing Tfh differentiation, fails to promote Tfh differentiation in middle-aged K/BxN mice, suggesting that most of the middle-aged Tfh cells with an effector phenotype are Tfh effector memory cells induced at an earlier age. Our results also indicate that exposure to immunomodulatory commensals may allow the young host to develop an overactive immune system reminiscent of that found in the middle-aged host.

In the gut-associated lymphoid tissues, Th17 cells mediate mucosal homeostasis and inflammation. During HIV infection, Th17 cells become depleted and functionally impaired, which is implicated in the pathogenesis of chronic inflammation in patients treated with highly active antiretroviral therapy. IL-7 is a cytokine that mediates homeostatic responses in T lymphocytes, such as proliferation and survival, which are dysregulated during HIV infection. Whether similar dysregulation occurs in Th17 cells has yet to be reported. IL-7 receptor α (CD127) expression and IL-7 responses were therefore measured in blood-derived Th17 cells from uninfected individuals and effectively treated, HIV-infected individuals by flow cytometry. Th17 cells from uninfected individuals expressed CD127 and, in response to IL-7, exhibited phosphorylation of STAT5, upregulation of Bcl-2, and proliferation. During HIV infection, expression of CD127 and pSTAT5 in Th17 cells was comparable to that observed in cells from uninfected individuals. Interestingly, expression of Bcl-2 was upregulated while proliferation was dramatically impaired. These findings may provide further insight into the mechanisms by which Th17 cells fail to become restored during HIV infection.