A asma acomete cerca de trezentos milhões de pessoas em todo o mundo. A doença é caracterizada por falta de ar, chiado e compressão no peito, tosse como consequência da hiperresponsividade brônquica e limitação de fluxo aéreo, causadas pela inflamação pulmonar Th2 e eosinofílica. Porém, existem evidências de que a IL-22 e a IL-17 participam da patogênese da asma alérgica. Com intuito de compreender melhor o papel da IL-22 na asma alérgica, utilizamos camundongos deficientes em IL-22 (IL-22KO) comparando-os aos animais Wild Type (WT) expostos ao alérgeno. Animais WT e IL-22KO foram sensibilizados e desafiados com ovalbumina (OVA) e avaliados quanto à inflamação eosinofílica, produção de citocinas, produção de muco, e populações celulares no pulmão. Nossos resultados mostram que a ausência de IL-22 resultou em diminuição da eosinofilia, IL-5 e IL-13 no lavado broncoalveolar, de células CD4+IL-4+ nos linfonodos e diminuição na produção de muco nas vias aéreas. Além disso, os camundongos IL-22KO alérgicos apresentam diminuição na porcentagem e número de células dendríticas CD11c+CD11b+CD103- nos pulmões quando comparados aos respectivo grupo WT. A transferência de células Th17 geradas a partir de animais IL-22KO causou diminuição na eosinofilia em camundongos expostos ao alérgeno quando os mesmos foram comparados aos animais que receberam células Th17 geradas a partir de animais WT. Esse resultado atribui mais à IL-22 do que à IL- 17 papel patogênico na asma alérgica. Outro indício da participação patogênica da IL-22 na asma alérgica é o fato de que o tratamento alérgeno específico, combinado ou não com a terapia livre de alérgeno, induziu redução da eosinofilia, do infiltrado de células dendríticas e diminuição de IL-22 no lavado broncoalveolar. A provável ação da IL-22 é a manutenção da viabilidade e sobrevivência de eosinófilos nos pulmões, fazendo que estes leucócitos continuem auxiliando no recrutamento de células dendríticas responsáveis pela captura e apresentação do alérgeno nos linfonodos, onde haverá a diferenciação de linfócitos de padrão Th2. Essas células podem migrar para os pulmões, gerando aumento na inflamação no local. Em síntese, nosso estudo corrobora o papel proinflamatório da IL-22 na asma alérgica e mostra, de forma inédita, que a transferência de células Th17 produtoras de ambas as citocinas, IL-22 e IL-17, mas não a transferência de células produtoras apenas de IL-17, causa exacerbação da inflamação pulmonar, possivelmente relacionada com o papel da IL-22 em prevenir indiretamente a indução de apoptose nos eosinófilos. / Asthma affects approximately three hundred million people worldwide. The disease is characterized by shortness of breath, wheezing and chest compression, coughing as a result of bronchial hyperresponsiveness and airflow limitation caused by Th2 lung inflammation and eosinophilia. However, there is evidence that IL-22 and IL-17 participate in the pathogenesis of allergic asthma. With the intention to better understand the role of IL-22 in allergic asthma, we used IL-22 deficient mice (IL-22KO) comparing them to wild type animals (WT) exposed to the allergen. Animals WT and IL-22KO were sensitized and challenged with ovalbumin (OVA), and assessed for eosinophilic airway inflammation, cytokine production, mucus production, and cell populations in the lungs. Our results show that the absence of IL-22 resulted in decreased eosinophilia, IL-5 and IL-13 in the bronchoalveolar lavage, CD4 + IL-4 + cells in the lymph nodes and decrease in mucus production in the airways. In addition, allergic IL-22KO mice have decreased percentage and number of dendritic cells CD11c + CD11b + CD103- in lungs when compared to their corresponding WT group. The transfer of Th17 cells generated from IL-22KO animals caused a reduction in eosinophilia in mice exposed to the allergen when they were compared to animals that received Th17 cells generated from WT mice. This result assigns more IL-22 than IL-17 pathogenic role in allergic asthma. Another indication of the pathogenic involvement of IL-22 in allergic asthma is the fact that the specific allergen treatment, combined or not with allergen-free therapy induced a reduction of eosinophilia, the dendritic cell infiltration and decreased IL-22 in bronchoalveolar lavage. The possible action of IL-22 is maintaining the viability and survival of eosinophils in the lungs, making these leukocytes remain helping in the recruitment of dendritic cells responsible for capture and allergen presentation in lymph nodes, causing differentiation in lymphocytes Th2. These cells can migrate to the lungs, resulting in increased inflammation at the site. In summary, our study confirms the proinflammatory role of IL-22 in allergic asthma and shows, in an unprecedented manner, the transfer of producing Th17 cells of both cytokines IL-22 and IL-17, but not the transfer of cells producing only IL-17, cause exacerbation of pulmonary inflammation, possibly related to the role of IL-22 on indirectly prevent induction of apoptosis in eosinophils.

A asma acomete cerca de trezentos milhões de pessoas em todo o mundo. A doença é caracterizada por falta de ar, chiado e compressão no peito, tosse como consequência da hiperresponsividade brônquica e limitação de fluxo aéreo, causadas pela inflamação pulmonar Th2 e eosinofílica. Porém, existem evidências de que a IL-22 e a IL-17 participam da patogênese da asma alérgica. Com intuito de compreender melhor o papel da IL-22 na asma alérgica, utilizamos camundongos deficientes em IL-22 (IL-22KO) comparando-os aos animais Wild Type (WT) expostos ao alérgeno. Animais WT e IL-22KO foram sensibilizados e desafiados com ovalbumina (OVA) e avaliados quanto à inflamação eosinofílica, produção de citocinas, produção de muco, e populações celulares no pulmão. Nossos resultados mostram que a ausência de IL-22 resultou em diminuição da eosinofilia, IL-5 e IL-13 no lavado broncoalveolar, de células CD4+IL-4+ nos linfonodos e diminuição na produção de muco nas vias aéreas. Além disso, os camundongos IL-22KO alérgicos apresentam diminuição na porcentagem e número de células dendríticas CD11c+CD11b+CD103- nos pulmões quando comparados aos respectivo grupo WT. A transferência de células Th17 geradas a partir de animais IL-22KO causou diminuição na eosinofilia em camundongos expostos ao alérgeno quando os mesmos foram comparados aos animais que receberam células Th17 geradas a partir de animais WT. Esse resultado atribui mais à IL-22 do que à IL- 17 papel patogênico na asma alérgica. Outro indício da participação patogênica da IL-22 na asma alérgica é o fato de que o tratamento alérgeno específico, combinado ou não com a terapia livre de alérgeno, induziu redução da eosinofilia, do infiltrado de células dendríticas e diminuição de IL-22 no lavado broncoalveolar. A provável ação da IL-22 é a manutenção da viabilidade e sobrevivência de eosinófilos nos pulmões, fazendo que estes leucócitos continuem auxiliando no recrutamento de células dendríticas responsáveis pela captura e apresentação do alérgeno nos linfonodos, onde haverá a diferenciação de linfócitos de padrão Th2. Essas células podem migrar para os pulmões, gerando aumento na inflamação no local. Em síntese, nosso estudo corrobora o papel proinflamatório da IL-22 na asma alérgica e mostra, de forma inédita, que a transferência de células Th17 produtoras de ambas as citocinas, IL-22 e IL-17, mas não a transferência de células produtoras apenas de IL-17, causa exacerbação da inflamação pulmonar, possivelmente relacionada com o papel da IL-22 em prevenir indiretamente a indução de apoptose nos eosinófilos. / Asthma affects approximately three hundred million people worldwide. The disease is characterized by shortness of breath, wheezing and chest compression, coughing as a result of bronchial hyperresponsiveness and airflow limitation caused by Th2 lung inflammation and eosinophilia. However, there is evidence that IL-22 and IL-17 participate in the pathogenesis of allergic asthma. With the intention to better understand the role of IL-22 in allergic asthma, we used IL-22 deficient mice (IL-22KO) comparing them to wild type animals (WT) exposed to the allergen. Animals WT and IL-22KO were sensitized and challenged with ovalbumin (OVA), and assessed for eosinophilic airway inflammation, cytokine production, mucus production, and cell populations in the lungs. Our results show that the absence of IL-22 resulted in decreased eosinophilia, IL-5 and IL-13 in the bronchoalveolar lavage, CD4 + IL-4 + cells in the lymph nodes and decrease in mucus production in the airways. In addition, allergic IL-22KO mice have decreased percentage and number of dendritic cells CD11c + CD11b + CD103- in lungs when compared to their corresponding WT group. The transfer of Th17 cells generated from IL-22KO animals caused a reduction in eosinophilia in mice exposed to the allergen when they were compared to animals that received Th17 cells generated from WT mice. This result assigns more IL-22 than IL-17 pathogenic role in allergic asthma. Another indication of the pathogenic involvement of IL-22 in allergic asthma is the fact that the specific allergen treatment, combined or not with allergen-free therapy induced a reduction of eosinophilia, the dendritic cell infiltration and decreased IL-22 in bronchoalveolar lavage. The possible action of IL-22 is maintaining the viability and survival of eosinophils in the lungs, making these leukocytes remain helping in the recruitment of dendritic cells responsible for capture and allergen presentation in lymph nodes, causing differentiation in lymphocytes Th2. These cells can migrate to the lungs, resulting in increased inflammation at the site. In summary, our study confirms the proinflammatory role of IL-22 in allergic asthma and shows, in an unprecedented manner, the transfer of producing Th17 cells of both cytokines IL-22 and IL-17, but not the transfer of cells producing only IL-17, cause exacerbation of pulmonary inflammation, possibly related to the role of IL-22 on indirectly prevent induction of apoptosis in eosinophils.

BACKGROUND: Recently, it is found that T-helper (Th) 22 cells are involved in different types of autoimmune and tumor diseases. But, till now, no study has been carried out to understand the involvement of these cells in cervical cancer (CC). METHODS: Flow cytometry was used to determine the expression of interferon gamma (IFN-gamma), Interleukin-22 (IL-22), IL-17 in the peripheral blood of healthy controls (HC), CIN and cervical cancer patients. From peripheral blood mononuclear cells (PBMCs), mRNA expression levels of Aryl hydrocarbon receptor (AHR), RAR-related orphan receptor C (RORC), TNF-alpha and IL-6 were respectively determined. Using the method of ELISA, plasma concentrations of IL-22, IL-17 and TNF-alpha were examined. RESULTS: Th22 and Th17 cells were elevated in CC and CIN patients. Th1 cells and the plasma concentrations of IL-22 in CC patients were significantly increased compared with HC. In CC patients, an increased prevalence of Th22 cells was associated with lymph node metastases. There was a positive correlation between Th22 and Th17 cells, but an approximately negative correlation between Th22 and Th1 cells in CC patients. The mRNA expression of RORC, TNF-alpha and IL-6 was significantly high in CC patients. CONCLUSIONS: Our results indicate that there is a higher circulatory frequency of Th22, Th17 and Th1 cells in CC which may conjointly participate in the pathogenesis and growth of CC.

Inflammation can be initiated by an innate immune sensor, followed by activation of a signal mediator, resulting in control of immune response by a signal regulator. Mammalian nucleotide-binding oligomerization domain protein 1 (Nod1) and Nod2 initiate host innate immune response by recognition of specific bacterial molecules, resulting in the production of pro-inflammatory cytokines, chemokines, and anti-microbial peptides. A candidate sequence of chicken Nod1 (ChNod1) was identified with no current evidence of ChNod2. Stimulation of transiently overexpressed ChNod1 and its mutants with mammalian Nod-specific ligands was not conclusive of the function of ChNod1 most likely due to self-activation of ChNod1. In vitro studies showed no significant difference in expression of Nod1, its signaling molecules and pro-inflammatory cytokines in stimulated chicken mononuclear cells with synthetic ligands for mammalian Nod1 or Nod2. A signal mediator, macrophage migration inhibitory factor (MIF) inhibits the random migration of macrophages. Chemotaxis assay using recombinant ChMIF (rChMIF) revealed a substantial decrease in migration of macrophages. qRT-PCR analysis revealed that the presence of rChMIF enhanced levels of IL-1β and iNOS during monocytes stimulation with LPS. Additionally, Con A-stimulated lymphocytes exhibited enhanced IFN-γ and IL-2 transcripts in the presence of rChMIF. IL-22, which may act as a signal regulator, is an important effector of activated Th1 and Th17 as well as natural killer cells during inflammation. Recombinant ChIL-22 alone did not have an impact on chicken embryo kidney epithelial cells (CKECs); however, co-stimulation of CKECs with LPS and rChIL-22 enhanced the production of pro-inflammatory cytokines and anti-microbial peptides. Furthermore, rChIL-22 alone stimulated acute phase reactants in chicken embryo liver cells. These effects of rChIL-22 were abolished by addition of rChIL22 binding protein. Taken together, these results indicate an important role of ChIL-22 on epithelial cells and hepatocytes during inflammation. In this project, we identified and characterized the avian inflammatory mediators ChNod1, ChMIF, and ChIL-22. Studying each of their biological function in avian inflammation, especially under pathogenic challenges in epithelial tissues will provide a foundation for understanding the role of these inflammatory mediators in mucosal immunity. / Ph. D.

Les bilharzioses hépatospléniques sont des maladies parasitaires provoquées essentiellement par Schistosoma japonicum et Schistosoma mansoni. Ces infections provoquent une fibrose hépatique sévère chez 5 à 20% des sujets infectées vivant en zone endémique. Plusieurs études ont démontré que le développement de cette fibrose était régulé par des cytokines et chemokines et que la susceptibilité génétique à cette maladie dépendait chez l'homme d'un locus majeur sur le chromosome humain 6 en position q23. L'IL-22 est une cytokine produite essentiellement par les lymphocytes T auxiliaires et les cellules NK et qui a été impliqué dans la protection du foie et de l'intestin chez la souris. Le gène IL22RA2 codant pour le récepteur inhibiteur soluble de l'IL-22 (IL-22BP) est localisé dans la région de susceptibilité à la FH (6q23). Nous avons donc étudié l'implication de l'IL-22 dans la pathologie bilharzienne par une approche immunogénétique. Notre étude démontre que la production d'IL-22 est augmentée en réponse aux œufs de S. japonicum et aux antigènes d'œufs de S. mansoni dans des cultures de cellules mononuclées du sang périphérique d'individus chinois et brésiliens vivant dans des zones endémiques. Le traitement par le Praziquantel, qui favorise l'élimination des parasites et la réversion de la fibrose, est associé à une augmentation des taux d'IL-22 en culture. Nous avons observé que dans le sang des patients chinois, l'IL-22 est produit majoritairement par les lymphocytes T CD4+ et des cellules CD3-CD4- ne produisant pas d'IL-17A. Les taux d'IL-22 en culture et la proportion des cellules CD3-CD4-IL22+ sont inversement corrélés à la FH. / Hepatosplenic schistosomiasis is a parasitic disease caused primarily by Schistosoma japonicum and Schistosoma mansoni. These infections cause severe hepatic fibrosis (HF) in 5-20% of infected subjects living in endemic areas. Several studies have shown that the development of this fibrosis was regulated by cytokines and chemokines. Our laboratory has shown that genetic susceptibility to HF map to a major locus on human chromosome 6 at position q23. IL-22 is a cytokine produced primarily by T cells and NK cells and has been involved in protecting the liver and intestine in mice. The gene IL22RA2, encoding the soluble inhibitor receptor of IL-22 (IL-22BP), is located in the region of susceptibility to HF (6q23). We therefore examined the involvement of IL-22 in schistosomiasis pathology by an immunogenetic approach. Our study shows that the production of IL-22 is increased in response to eggs of S. japonicum and egg antigens of S. mansoni in cultures of peripheral blood mononuclear cells from Chinese and Brazilian subjects living in endemic areas. Treatment with praziquantel, which helps eliminate parasites and reversion of HF, is associated with increased levels of IL-22 in culture. We observed that in the blood of Chinese patients, IL-22 is produced mainly by CD4+ T cells and CD3-CD4-cells that do not produce IL-17A. The levels of IL-22 in culture and the proportion of CD3+CD4-IL22+ are inversely correlated with HF. These observations suggest that IL-22 may play a protective role in HF. To confirm this implication, we performed association studies between SNPs located in IL22 and IL22RA2 genes and HF.

O espalhamento de raios X a baixo ângulo tem se mostrado uma poderosa ferramenta na ánalise estrutural de proteínas em solução. Estudos em condições próximas ao estado nativo podem ser realizados, permitindo a visualização tridimensional de proteínas ou complexos formados. A tese apresentada aborda a teoria envolvida para utilização desta ferramenta. Uma nova metodologia foi proposta para a determinação da massa molecular de proteínas em solução, utilizando apenas uma curva de SAXS em unidades arbitrárias, visto que até o momento, este procedimento era realizado em comparação com outra proteína padrão de peso molecular conhecido. Com relação à instrumentação científica, um equipamento de SAXS foi desenvolvido no Instituto de Física de São Carlos, permitindo agora que medidas de SAXS em proteínas em solução sejam realizadas no instituto. Clonagem, expressão e purificação foram realizadas para o domínio de ligação ao DNA da isoforma do receptor tireoideano humano, a caracterização experimental desta proteína foi realizada por anisotropia de fluorescência, crosslink e SAXS. Após formação do complexo DNA-proteína, F2-DBD hTR, o mesmo foi submetido a cristalização, os cristais obtidos para o complexo não apresentaram padrão de difração e modelos de baixa resolução foram gerados utilizando SAXS. Além disso, estudos de baixo ângulo foram realizados linha de SAXS do LNLS para a enzima ferredoxina redutase de leptospira interrogans e para o complexo formado por interleucina-22 e pelo receptor interleucina-22, sendo seus modelos tridimensionais resolvidos. / Small angle X-ray scattering has been proven to be a powerful tool in the structural analysis of proteins in solution. This technique permits the three-dimensional visualization of native proteins envelop at the level of nanometers. In this study we discuss the small angle X-ray scattering theory and we proposed a new methodology to determine the molecular weight of proteins in solution, using only SAXS curve in arbitrary units. Prior the development of this method, the proteins molecular weighs were calculated by comparison with another of known size, usually bovine serum albumin. We also assembled SAXS equipment at the Physics Institute of São Carlos, which will permits in house measurements; as well as the cloning, expression and purification of DBD hTR, followed by the characterization of this protein by fluorescence anisotropy, crosslink and SAXS. The DNA-protein complex, F2-DBD hTR, was subjected to crystallization assays. Although, the crystals obtained for the complex showed no pattern of diffraction we were able to generate low-resolution models for the F2-DBD hTR using SAXS analysis. Moreover, the studies of the protein LepFNR and the complex IL-22/IL-22R1 by small angle X-ray scattering were performed in the line of SAXS of the LNLS, and their threedimensional models were resolved

O espalhamento de raios X a baixo ângulo tem se mostrado uma poderosa ferramenta na ánalise estrutural de proteínas em solução. Estudos em condições próximas ao estado nativo podem ser realizados, permitindo a visualização tridimensional de proteínas ou complexos formados. A tese apresentada aborda a teoria envolvida para utilização desta ferramenta. Uma nova metodologia foi proposta para a determinação da massa molecular de proteínas em solução, utilizando apenas uma curva de SAXS em unidades arbitrárias, visto que até o momento, este procedimento era realizado em comparação com outra proteína padrão de peso molecular conhecido. Com relação à instrumentação científica, um equipamento de SAXS foi desenvolvido no Instituto de Física de São Carlos, permitindo agora que medidas de SAXS em proteínas em solução sejam realizadas no instituto. Clonagem, expressão e purificação foram realizadas para o domínio de ligação ao DNA da isoforma do receptor tireoideano humano, a caracterização experimental desta proteína foi realizada por anisotropia de fluorescência, crosslink e SAXS. Após formação do complexo DNA-proteína, F2-DBD hTR, o mesmo foi submetido a cristalização, os cristais obtidos para o complexo não apresentaram padrão de difração e modelos de baixa resolução foram gerados utilizando SAXS. Além disso, estudos de baixo ângulo foram realizados linha de SAXS do LNLS para a enzima ferredoxina redutase de leptospira interrogans e para o complexo formado por interleucina-22 e pelo receptor interleucina-22, sendo seus modelos tridimensionais resolvidos. / Small angle X-ray scattering has been proven to be a powerful tool in the structural analysis of proteins in solution. This technique permits the three-dimensional visualization of native proteins envelop at the level of nanometers. In this study we discuss the small angle X-ray scattering theory and we proposed a new methodology to determine the molecular weight of proteins in solution, using only SAXS curve in arbitrary units. Prior the development of this method, the proteins molecular weighs were calculated by comparison with another of known size, usually bovine serum albumin. We also assembled SAXS equipment at the Physics Institute of São Carlos, which will permits in house measurements; as well as the cloning, expression and purification of DBD hTR, followed by the characterization of this protein by fluorescence anisotropy, crosslink and SAXS. The DNA-protein complex, F2-DBD hTR, was subjected to crystallization assays. Although, the crystals obtained for the complex showed no pattern of diffraction we were able to generate low-resolution models for the F2-DBD hTR using SAXS analysis. Moreover, the studies of the protein LepFNR and the complex IL-22/IL-22R1 by small angle X-ray scattering were performed in the line of SAXS of the LNLS, and their threedimensional models were resolved

Crohn’s disease (CD) is an inflammatory disease of the gastrointestinal tract attributed to an aberrant immune response to environmental and microbial triggers. Individuals with CD exhibit an enrichment of pro-inflammatory strains of Adherent-Invasive E. coli (AIEC) and often report a relapse of symptoms following a period of acute psychological stress. Despite a known immunosuppressive role, the mechanism by which stress contributes toward the development and progression of intestinal inflammation remains unknown. Here, we use a well characterized model of restraint stress to investigate the influence of psychological stress on host protection against a CD-associated strain of AIEC. We found that stress results in profound intestinal dysbiosis, allowing for a complete dominance of Enterobacteriaceae. Interestingly, while stress alone drives a state of low-grade inflammation and loss of barrier integrity in the gut, in the presence of a pathobiont strain of AIEC, stress drives a substantially heightened inflammatory response which exacerbated the resultant loss of barrier integrity. Moreover, we have found stress induces an augmented nutritional immune response, providing AIEC a competitive niche against commensal bacteria lacking alternative methods of iron uptake. Further, we see that stress-induced glucocorticoids mediate broad apoptosis of the CD45+CD90+ lymphocytic population in the gut. The loss of this population prevents an appropriate IL-22 mediated response to dysbiosis. Accordingly, blocking glucocorticoid signalling or exogenous administration of IL-22 prevents the stress-induced expansion of AIEC. This work underscores the complex nature of psychological stress such that the combination of iron limitation and glucocorticoid mediated immune attrition are simultaneously required for the stress-induced expansion of AIEC. These findings present novel insight into the mechanistic consequences of glucocorticoid signalling on impaired immune function and the provision of an inflammatory environment, resulting in a distinct impact on CD susceptibility. As such, deeper insight regarding the complex underpinnings of CD will assist in efforts to design representative models and will strengthen the discovery of targeted therapeutics. / Thesis / Master of Science (MSc) / Crohn’s disease (CD) is an inflammatory disease of the gastrointestinal tract resulting from an exaggerated immune response. CD patients often report a relapse of symptoms following a period of psychological stress and are at an increased likelihood of having pro-inflammatory strains of E. coli within their gut. Here, we use a model of restraint stress to investigate how psychological stress modulates the abundance of bacterial species associated with CD. We found stress results in the limitation of essential nutrients, allowing for an outgrowth of E. coli. Further, stress hormones lead to the loss of a protective immune response in which E. coli expansion can be prevented by blocking these hormones or restoring immune signalling. Together, we conclude that stress leads to immune cell death and creates an iron limited environment that favours E. coli expansion. Such work begins to uncover the functional consequence of stress and its’ role in disease progression.

L’intestin des mammifères est colonisé par une dense communauté microbienne avec lequel il a établi, au cours d’une longue co-évolution, des relations mutualistes. Ces relations, bien qu’essentiellement basées sur des avantages métaboliques permettent également la maturation complète du système immunitaire, dont le développement est initié in utero par un programme génétique. Chez la souris, seule la SFB a été décrite comme présentant un fort pouvoir immunostimulant permettant la coordination d’un large panel de réponses immunes, notamment IgA et Th17 dont le site d’induction préférentiel serait les plaques de Peyer. La première partie de ma thèse a contribué à la finalisation de travaux consacrés à l’étude des caractéristiques des réponses IgA et Th17 induites par SFB. Nous avons ainsi mis en évidence la capacité de la SFB à stimuler la maturation post-natale de follicules lymphoïdes isolés et de tissus lymphoïdes tertiaires qui se substitueraient aux plaques de Peyer en tant que sites inducteurs des réponses IgA et Th17 stimulées par SFB. Cependant, ce microbiote constitue aussi une source antigénique importante pouvant représenter une menace pour l’intégrité de l’hôte. Notamment, la SFB peut provoquer une inflammation chronique délétère en périphérie de l’intestin, chez des souris prédisposées génétiquement. Cela suggère l’existence de mécanismes capables de réguler la colonisation par la SFB, afin d’éviter tout phénomènes compromettant l’intégrité physiologique de l’hôte. À l’aide de souris immunodéficientes axéniques ou seulement colonisées par SFB, nous avons pu mettre en évidence un rôle de la voie de signalisation des TLR dans le contrôle de la colonisation par SFB. Cependant, ni les peptides anti-microbiens, ni les IgA ne semblent impliqué dans le contrôle de la colonisation par SFB. / The mammalian intestine is heavily colonized by a huge microbial community. During a long coevolution process, the host has evolved mutualistic relationships with its microbiota. Thes relationships, mainly based on metabolstic advantages, also allow the full maturation of the host immune system, which development is initiated in utero by a genetic program. In mice, only SFB has been yet described to display strong immunostimulant properties allowing the coordination of a large panel of immune responses, more specifically IgA and Th17 responses, which preferential induction sites might be the Peyer's patches. The first part of my thesis contributed to complete a work dedicated to the characterization of the IgA et Th17 responses induced by SFB. We have underscored SFB capacity to stimulate the post-natal maturation of isolated lymphoid follicles and also tertiary lymphoid tissues that would substitute to Peyer's patches as inductors sites of both IgA and Th17 responses induced by SFB. However, this microbiote also constitutes a potential antigenic threat for the host integrity. Notably, the SFB could provoke chronic deleterious inflammation in peripheric compartment in genetically predisposed individuals. It suggests the establishment of highly regulated mechanisms regulating SFB colonization, to avoid compromising events for the host homeostasis. In a second part of my thesis, with the help of immunodeficient axenic mice, we have shown a role of TLR signaling pathways in the control of SFB colonization. However, antimicrobial peptides, IgA, IL-17 or IL-22 seem to be involved int eh control of SFB colonization.

La tuberculose est encore aujourd’hui un problème de santé majeur et l’augmentation des cas de tuberculoses résistantes au niveau mondial, associé au dépistage et diagnostic insuffisants, suggère une éradication totale encore lointaine. La compréhension des relations hôte-pathogène est essentielle pour permettre d’établir de nouvelles stratégies thérapeutiques. Ces travaux de thèse ont mis en exergue la contribution limitée de la voie de signalisation IL-36, cytokine de la famille de l’IL-1, au cours de l’infection mycobactérienne. Ces données permettent d’envisager sérieusement l’IL-36 en tant que cible thérapeutique pour le psoriasis sans risquer la réactivation de tuberculose latente chez les patients. De plus, nous avons également démontré le rôle différentiel de la voie de signalisation TNF au sein de populations cellulaires spécifiques lors de l’infection par M. tuberculosis, et nos résultats apportent des connaissances solides pour envisager des stratégies immuno-modulatoires qui pourraient constituer l’avenir des traitements antituberculeux. D’autre part, nous avons caractérisé un modèle murin humanisé pour une étude facilitée des anticorps anti-TNF humains actuels. L’utilisation de ce modèle pourrait permettre, à termes, d’identifier et de valider de nouveaux candidats d’anticorps anti-TNF de deuxième génération. Enfin, nous avons montré que des anticorps neutralisants l’IL-17 ne perturbent pas la réponse immunitaire à la tuberculose, contrairement aux anticorps anti-TNF, et que l’absence de l’IL-17 n’est pas compensée par l’IL-22 puisque des animaux déficients pour ces deux voies de signalisation sont capables de contrôler l’infection. / Tuberculosis remains a major health problem in the world nowadays. The increasing incidence of resistant tuberculosis is associated with a poor diagnosis, reflecting important difficulties for total eradication. Understand host-pathogen interactions is crucial to establish new therapeutic strategies. This work first shows the limited contribution of IL-36 pathway during mycobacterial infection. These results suggest that IL-36 could be targeted for the treatment of psoriasis without a high risk of tuberculosis reactivation. We then demonstrate the differential role of TNF pathway among myeloid or lymphoid cells during M. tuberculosis infection, and our data support the development of immunomodulatory strategies to boost host immune response, thus helping to clear the infection. Moreover, we characterize a humanized murine model allowing the study of new anti-TNF candidates in the context of M. tuberculosis infection. Finally, we show that antibodies targeting IL-17 does not dampen host control of M. tuberculosis infection, unlike anti-TNF, and that IL-22 does not compensate absence of IL-17 for this control.