Hepatitis C Virus (HCV) is one of the most important causes of chronic liver disease, affecting more than 170 million people worldwide. The mechanisms of hepatitis C pathogenesis are unknown. Viral cytotoxicity and immune mediated mechanisms might play an important role in its pathogenesis. HCV infection and alcohol abuse frequently coexist and together lead to more rapid progression of liver disease, increasing the incidence and prevalence of cirrhosis and hepatocellular carcinoma. The cytopathic effect of HCV proteins, especially the core, E1 and E2 structural proteins, which induce liver steatosis, oxidative stress and cell transformation may be amplified by alcohol abuse. The purpose of this study was to characterize the liver damage mechanisms induced by HCV structural proteins and alcohol and to determine the potential molecular mechanism(s) that may promote chronic, progressive liver damage. A transgenic mouse model expressing HCV core, E1 and E2 was used to investigate whether alcohol increased HCV RNA expression. Real-time RT-PCR analysis of genes involved in lipid metabolism and transport confirmed their abnormal expression in the alcohol-fed transgenic mice. In addition, light and electron microscopy analysis were performed on liver tissues of transgenic mice on an alcoholic diet versus those on a normal diet, in order to identify histological changes. The severe hepatopathy in HCV transgenic mice was exacerbated by alcohol. Mitochondria and endoplasmic reticulum had severe abnormalities in the electron microscopy analysis. The second part of this study focused on adaptive immune responses, which may also play an important role in HCV pathogenesis. I focused my analysis on dendritic cells (DC), which have been the main suspects to explain immune impairment in HCV infection. Their powerful antigen-presenting function allows them to stimulate the antiviral response of CD4+ and CD8+ T cells, the effector cells of the immune system. This unique function of the DC makes them possible targets for immune evasion by the Hepatitis C virus. In this study, DCs were generated from mouse bone marrow cells. I investigated their maturation capacity in the presence of structural proteins of HCV. The impact of HCV core/E1/E2 polyprotein on DCs cytokine expression and ability to activate T-cell lymphocytes was also analyzed. A dysfunctional CD4 T cell response was observed after exposure of DCs to core/E1/E2 polyprotein, indicating inefficient CD4 priming, which might lead to chronic HCV infection in humans. The presence of the core/E1/E2 polyprotein reduced the DC maturation capacity and the expression of certain cytokines (IL-12, IFNg, IL-6, MCP-1) important for stimulation and chemotaxis of T cells and other immune cells. My studies contribute to the understanding of HCV pathogenesis and may have implications to the development of better therapies for HCV infection.

Embryonic stem cells (ESC) possess immune privileged properties and have the capacity to modulate immune activation. ESCs can persist across allogeneic immunological barriers, prevent lymphocyte proliferation in mixed lymphocyte reaction (MLR) assays and can promote graft acceptance. However, clinical application of live ESC to treat immunological disorders is not feasible as live ESC can form teratoma in-vivo. In order to harness these properties of ESCs without adverse risk to patients, we hypothesized that ESC derived extracts may retain immune modulatory properties of whole cells and therefore could be used to abrogate allo-immune responses. We found addition of ESC-extracts from human lines H1 and H9, significantly prevented T cell proliferation in allogeneic MLRs. These results were confirmed using murine J1 ESC line. In-vitro studies showed human ESC EXT were able to modulate maturation of human monocyte derived dendritic cells (DC) by suppressing up-regulation of important co-stimulatory and maturation markers CD80, HLA-DR and CD83. In addition, DCs educated in the presence of human ESC extracts significantly lost their ability to stimulate purified allogeneic T cells compared to control extract treated DCs. We also determined that ESC extracts have an independent effect on T cells. ESC extracts prevented T cell proliferation in response to anti CD3/CD28 stimulation. In MLRs, ESC derived factors significantly down-regulated IL-2 and IFN-γ expression, while up-regulating TGF-β and Foxp3 expression. Furthermore, lymphocytes and purified T cells activated with anti-CD3/CD28, ConA and PMA proliferated poorly in the presence of ESC derived factors, while proliferation in response to ionomycin was not affected. Western blot analysis indicated that ESC derived factors prevented PKC-θ phosphorylation without influencing total PKC-θ levels. Moreover, IκB-α degradation was abrogated, confirming absence of PKC-θ activity. Therefore, ESC extracts have potent immune suppressive properties and may have clinical applications in ameliorating transplant rejection and autoimmune conditions.

Salmonella enterica serovar Typhimurium (ST) is an intracellular bacterium that resides within the phagosome of infected cells. ST is the causative agent of gastroenteritis in humans and typhoid like disease in mice. ST infects epithelial cells and phagocytic cells such as dendritic cells (DCs), which are immune sentinels that have been regarded as the most critical antigen-presenting cell (APC). I evaluated the role of CD8α DCs, a subset of DCs capable of antigen presentation of phagosomal pathogens to activate CD8+ T cells. Furthermore, I assessed the role of key cytokines such as the group of classical anti-viral cytokines known as Interferon-I (IFN-I), on licensing CD8+ T cells. Interestingly, IFN-I signalling was necessary for production of inflammatory cytokines and induction of cell death, which activated CD8+ T cells and clearance of ST. Lastly, I examined the role of key cell death pathways in innate immune protection against ST. In particular, I addressed how signalling pathways in necroptosis and pyroptosis are critical for the production of IL-1beta and IL-18 which mediate immune protection against ST. Determining the mechanisms of which DCs engage innate and adaptive immune responses against phagosomal bacteria is the central question of my study and is addressed by examining critical roles of DC function, inflammation and cell death.

Les cellules dendritiques, puissantes cellules présentatrices d'antigène, jouent un rôle-clé dans l'initiation et la régulation des réponses immunitaires et inflammatoires (Lipscomb et al., 2002). Elles sont présentes à l'état de cellules immatures dans la plupart des muqueuses, disséminées dans le tissu interstitiel et les épithéliums. Elles sont chargées de capter les antigènes exogènes, de les apprêter et de migrer vers les organes lymphoïdes pour les présenter aux lymphocytes T spécifiques. Au cours de cette migration, elles acquièrent les caractéristiques des cellules dendritiques matures présentes dans les organes lymphoïdes (expression forte des molécules HLA de classe II et des molécules de costimulation CD40, CD80, CD83, CD86). Les cellules dendritiques sont présentes dans le poumon normal (Vermaelen et al., 2005). Elles sont impliquées dans la physiopathologie de différentes maladies pulmonaires et jouent un rôle pathogénique essentiel dans certaines d'entre elles comme l'histiocytose langerhansienne ou l'asthme (Tazi et al ., 2000; Lambrecht et Hammad, 2003). Leur rôle au cours des processus fibrosants n'a cependant jamais été évalué. En effet, contrairement à d'autres cellules présentatrices d'antigènes que sont les macrophages, dont le rôle dans la réaction fibrosante est clairement établi (Agostini et al ., 1997), le rôle des cellules dendritiques au cours des processus de réparation alvéolaire n'a pas été étudié. Notre travail visait à étudier in vivo le rôle des cellules dendritiques au cours de la fibrose pulmonaire sur un modèle animal par induction d’une fibrose à la bléomycine chez la souris. Les premières étapes du projet ont consisté à caratériser par cytométrie en flux la présence de cellules dendritiques dans le poumon des animaux 3, 7 et 14 jours après instillation intratrachéale de bléomycine. L'étude s'est poursuivie par une caractérisation du phénotype de surface des cellules dendritiques en cherchant à préciser leur état d’activation et de maturation. L'étape suivante a consisté à rechercher par RT-QPCR les principales chimiokines responsables du recrutement des cellules dendritiques. Les résultats montrent une augmentation du nombre des cellules dendritiques CD11c+ / CMH II+ infiltrant le poumon dès J7, avec une sous-population de cellules activées exprimant fortement les molécules CMH II. Ces résultats sont corroborés par une augmentation de la population cellulaire totale du broyat de poumon dès J3, ainsi que par une augmentation de la cellularité totale et du nombre de cellules inflammatoires dans les lavages bronchoalvéolaires (LBA) à J7 et J14. L'étude a été complétée par une caractérisation plus approfondie du phénotype de surface des cellules dendritiques en cherchant à préciser leur état d’activation/maturation. [...] / Dendritic cells (DCs), potent antigen-presenting cells, play a key role in the initiation and regulation of immune and inflammatory responses (Lipscomb et al., 2002). Immature DCs are present in the most of mucous membranes, disseminated in the interstitial tissue and the epithelia. They are able to deal with exogenous antigens, to process them and to migrate to lymphoid organs and to present them to T lymphocytes. During their migration, they have the characteristics of mature DCs in lymphoid organs (higher expression of MHC class-II molecules and costimulation-molecules (CD40, CD80, CD83, CD86). Dendritic cells are present in the normal lung (Vermarlen et al., 2005). They are implicated in the pathophysiology of different pulmonary diseases and play a crucial pathogenic role in some of them like Langerhan’s cell Histiocytosis or asthma (Tazi et al., 2000; Lambrecht et Hammad, 2003). However, their role in the fibrosing process has never been studied. In fact, the role of macrophages (other antigen presenting cells (APCs)) in fibrosing reaction has been clearly established (Agostini et al., 1997), but DCs function during the alveolar healing process has not been studied. The purpose of this thesis is to study the in vivo role of DCs in bleomycin-induced pulmonary fibrosis in mice. The first step of this project is to demonstrate by flow cytometry the presence of DCs in the lung of these animals 3, 7 and 14 days after intratracheal bleomycin instillation. We continued our research with the surface phenotypic characterization of DCs identifying their activation state and maturation. The next step consists to search the main chemokines which are responsive for dendritic cells recruitment by RT-qPCR. Our results show an increase of CD11c+ / MHC class II+ DCs number infiltrating the lung after D7, with an activated cell subpopulation which strongly express MHC class II molecules. The results are corroborated by an increase of the total cell population in the lung homogenate after D3 and by an increase of the total cellularity and inflammatory cells number in broncho-alveolar lavages (BAL) at D7 and at D14. This study was completed by the surface phenotypic characterization of DCs identifying their activation state and maturation. [...]

As the principal antigen-presenting cells to T cells, dendritic cells (DCs) have a key role in the balance of immunity and autoimmunity. They are essential in two major, converse roles - eliciting T cell immune responses to pathogenic material, and maintaining peripheral tolerance to self-tissue by inhibiting self-reactive T cells. These functions involve the processing of pathogenic or self antigens and subsequent presentation of antigenic peptides on MHC to antigen-specific T cells. DC recognition of conserved pathogenic markers induces a mature phenotype that governs immunogenic presentation to T cells and, consequently, the adaptive immune response. In contrast, DC recognition of self tissue suppresses maturation, instead inducing a tolerogenic phenotype that induces self antigen-specific T cell to die, become anergised, or converted to T regulatory cells. Apoptotic cells are the major source of self-antigen for the maintenance of peripheral tolerance, and their defective clearance by DCs is implicated in autoimmunity. Apoptotic cells are thought to actively suppress maturation of DCs and inhibit the possible immune responses promoted by proinflammatory mediators released from necrotic cells. However, the immune function of apoptotic cells and their relative influence over necrotic cells are highly contested, partially due to the complex nature of immunogenicity arising from the sourcing and generation of apoptotic cells. In this investigation, various methods of inducing apoptosis and necrosis are evaluated. Definitive methods of inducing well-characterised cell death are then employed to compare the effects of apoptotic and necrotic cells on dendritic cells and in vitro and in vivo immune responses. Reported here are in vitro findings that support previous reports of the anti-inflammatory response of DCs to apoptotic cells, and the inflammatory response of DCs to necrotic cells. The previously-reported inhibitory effect of apoptotic cells on LPS-induced secretion of Th1 cytokines is supported here, but the inhibitory effect of apoptotic cells on LPS-induced upregulation of co-stimulatory molecules is contested. Novel findings describe the upregulation of DC expression of co-inhibitory molecules induced by both apoptotic cells and necrotic cells. Apoptotic cells, but not necrotic cells, had a suppressive effect on CpG-induced upregulation of co-stimulatory molecules and pro-inflammatory cytokines. Apoptotic cells suppressed the capacity of untreated and CpG-treated, but not LPS-treated, DCs to elicit IFNγ production by T cells. Apoptotic cells, but not necrotic cells, induced regulatory T cells and partially restored their CpG-suppressed induction. Finally, apoptotic cell-modulation of DCs inhibited the induction of autoimmunity in a novel modification of an in vivo model of diabetes. Interestingly, novel evidence for the possibility of necrotic cell-induced tolerance by means of direct T cell killing is addressed.

Trichuris trichiura (T. Trichiura) is a large-intestinal dwelling nematode that affects over 1 billion people world-wide and thus has large global significance. Much of our understanding of T. trichiura infection comes from the study of the mouse model Trichuris muris (T. muris). However, how the immune system is initiated in response to helminth threat and how inflammation and pathology are resolved in T. muris infection still remain to be addressed. Here, I have attempted to provide insight into these questions. Previous work has shown resistance to T. muris infection is associated with the rapid recruitment of dendritic cells (DCs) to the colonic epithelium via epithelial production of CCL5 and CCL20. However, the epithelial-parasite interaction that drives chemokine production is not known. Pattern recognition receptor (PRRS) are critical mediators of pathogen recognition but there is no known (PRR) specific for T. muris. Here, we address the role of the cytosolic pattern recognition receptor Nod2, the location of which within the crypts correlates with the T. muris niche. In WT mice, in response to infection, there was a rapid influx of CD103+CD11c+ DCs into the colonic epithelium, whereas, this recruitment was impaired in Nod2 /- animals. In vitro and in vivo experiments confirmed the impairment in DC recruitment in Nod2-/- mice was attributable to the epithelial compartment. Subsequent work revealed decreased production of epithelial chemokines in the absence of functional Nod2. Thus, we have shown a novel role for Nod2 in the initiation the immune response to T. muris. We next addressed how pathology is regulated during T. muris infection. Firstly we investigated the role of arginase and Arg1-expressing macrophages in regulating pathology. My data showed that, unlike other gastrointestinal helminths, arginase and Arg1-expressing macrophages are not essential for resistance to T. muris or effective resolution of helminth-induced inflammation. I also addressed the role of DCs in the resolution of infection. DCs can regulate immune responses via the anti-inflammatory cytokine IL-10 and induction of regulatory T cells (Treg). I used an IL 10flox/floxCD11cCre transgenic model in which mice have DCs that cannot make IL-10. I found no role for CD11c+ cell mediated IL-10 production in the regulation of pathogen induced pathology in chronic T. muris infection. In summary I have been able to identify factors in the initiation of immunity to T. muris namely epithelial expression of Nod2. However, as arginase, Arg1-expressing macrophages and DC derived IL-10 appeared to play a redundant role in T. muris infection, the question as to how infection induced inflammation is resolved remains elusive.

Orientadores: Maria Marluce dos Santos Vilela, Taís Nitsch Mazzola / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-26T10:36:44Z (GMT). No. of bitstreams: 1 Bernachi_JessicaSantana_M.pdf: 2518686 bytes, checksum: 58cf0214c9aa6fb37c051da8088bd63a (MD5) Previous issue date: 2014 / Resumo: A vacinação terapêutica com células dendríticas derivadas de monócitos (MDDC) têm sido associada com o controle da carga viral em adultos infectados pelo HIV, mas os seus efeitos em crianças não foram explanados. Nesse sentido, o objetivo deste trabalho foi avaliar a função das MDDC isoladas de crianças e adolescentes verticalmente infectados pelo HIV sob terapia antiretroviral combinada. Os pacientes foram recrutados no Ambulatório de Imunodeficiência Secundária Pediátrica do Hospital de Clínicas da Universidade Estadual de Campinas, sendo 25 com carga viral indetectável e 14 com carga viral ?1000 cópias de RNA/mL. Além disso, 20 crianças e adolescentes saudáveis participaram como controles. Monócitos obtidos do sangue periférico foram cultivados durante seis dias com GM-CSF e IL-4 para a obtenção das MDDC, as quais foram avaliadas por citometria de fluxo quanto à expressão de CD40, CD80, CD83, CD86, DC-SIGN e HLA-DR. As MDDC foram pulsadas com HIV-1 inativado por aldritiol-2 e cocultivadas com linfócitos autólogos para avaliação da expressão gênica e proteica de citocinas e da linfoproliferação HIV específica. Foram avaliados também hemogramas, subpopulações de células dendríticas mielóides e plasmocitóides e de linfócitos CD3, CD4 e CD8. As MDDC dos pacientes infectados pelo HIV apresentaram um fenótipo semelhante aos controles saudáveis e foram capazes de induzir a produção de citocinas do tipo Th1; no entanto, crianças com carga viral ?1000 cópias de RNA/mL apresentaram menor linfoproliferação HIV-específica. Em geral, as MDDC de crianças verticalmente infectadas pelo HIV geradas in vitro foram capazes de induzir resposta imune celular HIV específica, mostrando-se potenciais candidatos para imunização terapêutica usando MDDC / Abstract: Therapeutic vaccination with monocyte-derived dendritic cells (MDDC) has been associated with viral load control in immunized HIV-infected adults, but its effects in children were not explored yet. We aimed to evaluate the function of MDDC isolated from vertically HIV-infected children and adolescents under combined antiretroviral therapy. Patients were recruited at the Out-Patients Unit at the University of Campinas, which 25 patients had undetectable viral load and 14 patients had viral load ?1000 RNA copies/mL. In addition, 20 healthy children and adolescents served as controls. Monocytes obtained from peripheral blood were cultured for six days with GM-CSF and IL-4 to get the MDDC, which were assessed by flow cytometry for CD40, CD80, CD83, CD86, DC-SIGN and HLA-DR expression. T cell proliferation and cytokine expression and production were evaluated in cocultures of MDDC pulsed with aldrithiol-2-inactivated HIV-1 and autologous lymphocytes. Hemogram, myeloid and plasmacytoid dendritic cells and CD3, CD4 and CD8 lymphocytes were evaluated in the peripheral blood. MDDC from HIV-infected children exhibited a similar phenotype to those in healthy individuals and were able to induce a Th1-type cytokine production; however, T lymphoproliferation was impaired in children with viral load ?1,000 RNA copies/mL. MDDC generated in vitro boosted HIV-specific cellular immune responses in vertically HIV-infected children and could be potential candidates for MDDC therapeutic immunization / Mestrado / Saude da Criança e do Adolescente / Mestra em Ciências

Les adjuvants vaccinaux permettent d’augmenter la réponse immunitaire dirigée contre un antigène donné. Certains de ces adjuvants miment des signaux de danger, tels que des agonistes des récepteurs de l’immunité, les récepteurs Toll-like (TLR) ou les récepteurs NOD-like (NLR), et permettent une activation des cellules dendritiques (DC). Les DC sont essentielles dans la mise en place d’une réponse adaptative contre un antigène : elles acquièrent un phénotype mature, contrôlé par les voies des MAPK et NF-κB, permettant la présentation de l’antigène aux lymphocyte T et l’initiation d’une réponse spécifique. La voie Nrf2/Keap1, impliquée principalement dans la détoxication des xénobiotiques et le contrôle du stress oxydant, peut être activée en réponse à des agonistes des TLR tels que le LPS (agoniste TLR 4). Nous avons mis en évidence qu’un traitement par le R848 (agoniste TLR7/8) ou le MDP (agoniste NOD2) induit la transcription des gènes cibles de Nrf2 dans les DC murines. Nrf2 participe également à la production de cytokines inflammatoires en réponse au LPS et au R848 et jouet un rôle dans la prolifération lymphocytaire induite par les DC pré-traitées avec le MDP. Par ailleurs, Nrf2 contrôle la réponse anticorps spécifiques de l’antigène chez la souris. L’injection d’anatoxine tétanique induit une production d’anticorps plus élevé chez la souris déficiente nrf2 par rapport aux souris sauvages. Cette augmentation de la production d’anticorps est corrélée avec une augmentation du nombre de lymphocyte B dans la moelle osseuse et la rate. / Vaccine adjuvants are able to boost immune response toward antigens when there are simultaneously injected. Some of these adjuvant mimic danger signals, such as Toll like receptors (TLR) agonists or NOD-like receptors agonists, required for dendritic cell (DC) activation. DC are essentiales for adaptative immune response against antigens : they acquire mature phenotype, controlled by MAPK and NF-kB signaling pathway, leading to antigen presentation and specific immune response. The Nrf2/keap1 signaling pathway, mainly involves in xenobiotics detoxication and oxidative stress control, can be activate by TLR agonists, such as LPS (TLR 4 agonist).We showed that R848 (TLR 7/8 agonist) and MDP (NOD2 agonist) could induce Nrf2’s target genes transcription in murines dendritic cells (BMDC). Nrf2 seems also to be part of inflammatory cytokines production in response to LPS or R848 and modulated T lymphocyte proliferation induced by MDP pre-treated BMDC. Moreover, Nrf2 appears to play a role in specific antibodies response against an antigen in mice. . In fact, Tetanus toxoid (TT) injection induces higher titer of antibodies anti-TT in nrf2-/- mice compared to nrf2+/+ mice. This increase is also correlated with more specific B lymphocytes in bone marrow and spleen after TT immunisation.

No description available.

TSSP (Protéase à Sérine Spécifique du Thymus) est une protéase exprimée de manière prépondérante dans le thymus par les cellules épithéliales thymiques corticales (cTEC) et par les cellules dendritiques thymiques (tDC). En revanche, TSSP n'est pas exprimée par les cellules dendritiques (DC) en périphérie même après activation par des agonistes de TLR (Toll-like Receptor). L'équipe a précédemment montré que les souris NOD déficientes pour TSSP (NOD TSSP°) sont totalement résistantes au développement du diabète de type 1 (T1D) contrairement aux souris NOD WT qui développent de manière spontanée la pathologie. L'absence de T1D est due à une augmentation de la sélection négative de cellules T CD4 spécifiques de certains antigènes des ilots de Langerhans par les tDC. Ainsi, la déficience en TSSP conduit à l'épuration du répertoire des cellules T CD4 auto-réactifs par des évènements de sélection négative dans le thymus limitant ainsi le développement du T1D. Bien que la fonction précise de TSSP reste inconnue, ces données et des données complémentaires montrent que TSSP dans les tDC limite la présentation de certains antigènes des ilots de Langerhans dans la voie classe II. Nous avons, dans un premier temps, déterminé si le rôle de TSSP peut être généralisé à une autre maladie auto-immune médiée également par les cellules T CD4, l'encéphalomyélite auto-immune expérimentale (EAE), un modèle murin de sclérose en plaque. Nous avons montré que la sévérité de l’EAE induite par immunisation avec le peptide MOG35-55 (Glycoprotéine de l'Oligodendrocyte de la Myéline) est réduite chez les souris NOD TSSP°. La réduction de sévérité chez les souris NOD TSSP° est associée à une augmentation de la délétion des cellules T CD4 spécifiques du peptide MOG35-55. TSSP limiterait la délétion thymique des cellules T CD4 spécifiques de MOG35-55. Ainsi TSSP, en réduisant le répertoire peptidique présenté par les molécules I-Ag7, conduirait à un défaut de tolérance centrale favorisant le développement de maladies auto-immunes. Dans un second temps, l’objectif de mes travaux de thèse a été d'apporter de nouvelles connaissances quant à la fonction de TSSP dans les tDC. L’ensemble des données suggèrent que TSSP limiterait la présentation d’antigènes dans la voie classe II, nous avons donc analysé les capacités d’internalisation et de dégradation des tDC par imagerie en flux. Nous avons montré que TSSP limite spécifiquement l'internalisation de la protéine ovalbumine dans les cellules dendritiques conventionnelles 2 (cDC2) et dans une lignée de DC mais n'affecte pas leurs capacités dégradatives. De plus, la réduction de l’internalisation des antigènes dans les tDC de souris NOD WT est indépendant de l’endocytose médiée par récepteur. Ces données suggèrent que TSSP en réduisant l'internalisation des antigènes pourrait limiter la formation de complexes peptide/CMH II et la présentation antigénique dans la voie classe II. Par ce mécanisme, TSSP induirait un défaut de tolérance centrale et favoriserait le développement de maladies auto-immunes. / TSSP (Thymus Specific Serine Protease) is a protease expressed predominantly in the thymus by thymic epithelial cortical cells (cTEC) and thymic dendritic cells (tDC). In contrast, TSSP is not expressed by dendritic cells (DC) in the periphery even after activation by TLR agonists (Toll-like Receptor). Previous studies showed that TSSP-deficient NOD mice are completely resistant to the development of type 1 diabetes (TD1) whereas NOD WT mice spontaneously develop pathology. The absence of T1D is due to an increase in the negative selection, by tDC, of CD4 T cells specific for certain antigens of the islets of Langerhans. Thus, TSSP deficiency leads to the crippling of the autoreactive CD4 T cells repertoire by negative selection in the thymus limiting the development of T1D. Although the precise function of TSSP remains unknown, these data and complementary data show that TSSP in tDC limits the presentation of certain islet antigens in the class II pathway. At first, the aim of my PhD work was to determine if the role of TSSP can be generalized to another autoimmune disease also mediated by CD4 T cells, experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. We have shown that the severity of EAE induced by immunization with MOG35-55 (Myelin Oligodendrocyte Glycoprotein) peptide is reduced in NOD TSSP° mice. Reduced disease severity is linked to increased deletion of MOG35-55 specific CD4 T cells in TSSP-deficient NOD mice. TSSP would limit the thymic deletion of MOG35-55 specific CD4 T cells. Thus, by reducing the peptide repertoire presented by the IAg7 molecules, TSSP would limit central tolerance and favor the development of autoimmune diseases. In continuation, the second objective of my thesis work was to clarify the function of TSSP in tDC. Given the suspected role of TSSP in the class II pathway we analyzed the internalization and degradation capabilities of tDCs by flow imaging. We have shown that TSSP specifically limits the internalization of ovalbumin protein in conventional dendritic cells 2 (cDC2) and in a DC line but does not affect the degradation of endocytosed OVA. The reduction of antigens internalization in the tDC of NOD WT mice is independent of receptor-mediated endocytosis. These data suggest that, by reducing internalization of antigens, TSSP could limit the formation of peptide/MHC II complexes and antigenic presentation in the class II pathway. By this mechanism, TSSP induces a defect of central tolerance and promotes the development of autoimmune diseases