Mon étude a porté sur le rôle du récepteur purinergique P2X7 (P2X7R) dans les processus physiopathologiques impliqués dans le développement des maladies auto-immunes de type lupique. Les souris MRL/lpr, déficientes en récepteurs d’apoptose Fas (mutation lpr), développent spontanément ces pathologies suite à l’accumulation lymphocytes T pathogéniques CD4−CD8− (DN) B220+ dans les organes lymphoïdes secondaires. Nous avons observé que ces lymphocytes ont également un déficit d’expression en P2X7R à leur surface. Cela nous a amené à postuler que P2X7R pourrait jouer un rôle clé dans l’homéostasie des lymphocytes T et le développement du lupus. Afin de vérifier notre hypothèse, nous avons produit des souris C57BL/6J (B6) déficientes simultanément pour Fas (lpr) et P2X7R (P2X7KO). Ces souris présentent une accumulation massive de lymphocytes T DN B220+ et des titres très élevés en auto-anticorps et en cytokines proinflammatoires ce qui n’est pas le cas pour les souris B6 simples mutantes lpr ou P2X7KO confirmant pour la première fois l’implication de P2X7R dans l’homéostasie des lymphocytes T, en synergie avec le récepteur Fas. Les lymphocytes T DN pathogéniques responsables de la lymphoaccumulation sont issues majoritairement de la sous populations des lymphocytes T CD8+. L’inflammation chronique présente chez les souris B6/lpr P2X7KO induit l’activation de l’ensemble des populations lymphocytaires T CD4+ et CD8+ naïves conduisant à l’accumulation de lymphocytes T Effecteurs/Mémoires : EM et CM et atteignent parfois le stade exhausted PD1+TIM3+. Ces cellules accumulées CD4+, CD8+ et DN B220+ ont une capacité de réactivation réduite. Ce biais fonctionnel et phénotypique a été confirmé en comparant la réponse immunitaire adaptative anti-adénovirus entre des souris déficientes en Fas et/ou P2X7R. Les réponses cellulaires et humorales sont moins importantes dans les souris B6/lpr P2X7KO que B6, B6-P2X7KO. Ces réponses antivirales sont intermédiaires dans les souris B6/lpr. L’ensemble de ces résultats renforcent notre hypothèse sur le rôle synergique des récepteurs Fas et P2X7R dans l’homéostasie des lymphocytes T. Le taux d’apoptose induit par l’activation des récepteurs Fas ou P2X7R séparément est moins important dans les lymphocytes T CD8+ par rapport au lymphocytes T CD4+. La synergie Fas-P2X7R serait donc nécessaire pour l’homéostasie des lymphocytes T CD8+. Afin de préciser les mécanismes à l’origine de la maladie et d’identifier l’influence de chaque récepteur sur l’expression des loci de susceptibilité, nous avons séquencé les ARNm exprimés dans la rate et les ganglions lymphatiques des souris MRL/lpr avant et après le développement de l’auto-immunité ainsi que chez les souris B6, B6/lpr, B6 P2X7KO et B6/lpr P2X7KO. / My project aims to determine the role of the purinergic receptor P2X7 (P2X7R) in the pathophysiological processes involved in the development of autoimmune lupus-like syndrome. MRL/lpr mice, deficient for the cell death receptor Fas (lpr mutation), spontaneously develop this pathology following the accumulation of pathogenic B220+CD4−CD8− (DN) T lymphocytes in secondary lymphoid organs. We have observed that these lymphocytes are also deficient in P2X7R cell surface expression. This led us to hypothesize that P2X7R could play a key role in T cell homeostasis and lupus development. To test our hypothesis, we produced B6 mice deficient for both Fas (lpr) and P2X7R (P2X7KO). These mice, but not single mutant B6 mice (lpr or P2X7KO), develop a massive accumulation of DN B220+ T lymphocytes and high levels of autoantibodies and proinflammatory cytokines, confirming for the first time the involvement of P2X7R in T-cell homeostasis. I have found that the pathogenic DN T lymphocytes are predominantly derived from the CD8+ T lymphocyte subpopulation. Chronic inflammation in B6/lpr P2X7KO mice induces the activation of the whole CD4+ and CD8+ naïve T lymphocyte subpopulations leading to the accumulation of Effector/Memory and exhausted T lymphocytes. Accumulated T-cells lose the ability to be reactivated. To confirm these results, I compared the adaptive immune response against adenovirus between mice deficient for Fas (lpr mutation), P2X7R-deficient mice or both receptors. The cellular and the humoral responses were lower in the B6/lpr-P2X7KO mouse strain compared to B6, B6-P2X7KO and B6/lpr mouse strains. The antiviral immune response in the B6/lpr mice was lower than in B6 and B6-P2X7KO mice. These results reinforce our hypothesis about the synergistic role of both receptors in the maintaining of T cell homeostasis. Ours results suggest that Fas and P2X7R play their synergistic role in T-cell homeostasis. In collaboration with a team from the University of Taiwan, we sequenced the mRNAs expressed in the spleen and lymph nodes of MRL/lpr mice before and after the onset of the diseases as well as in the B6, B6/lpr, B6 P2X7KO and B6/lpr P2X7KO mouse strains in order to better understand the mechanism triggering the disease and to identify the role of each receptor on the expression of the susceptibility loci.

京都大学 / 0048 / 新制・課程博士 / 博士(医科学) / 甲第20056号 / 医科博第74号 / 新制||医科||5(附属図書館) / 京都大学大学院医学研究科医科学専攻 / (主査)教授 浅野 雅秀, 教授 岩井 一宏, 教授 生田 宏一 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Eimerian parasites infect cattle worldwide. Information on the infection dynamics of these parasites is lacking in the central Appalachian region of the United States. Studies aimed at characterizing the seasonal dynamics of eimerian parasites in this region were carried out in order to assess the impact of these organisms in grazing systems. In these studies the prevalence of Eimeria spp. infection was highest in calves less than one year of age and subsequently decreased to stable levels in older animals. Although E. bovis was the most common species identified in calves, heifers and cows, mixed species infections dominated. Additional studies were carried out to investigate the effect of stress on Eimeria spp. infection in beef calves. Lower stress, two-stage, weaning methods had no effect on Eimeria spp. infection dynamics in beef calves. These findings must be interpreted in light of the fact that calves used in this study were not managed in a way typical of many calves in the U.S.A. The fact that they were only transported short distances, never commingled, or exposed to a livestock market may explain why a rise in post weaning FOC was not observed. A model of stress- induced coccidiosis was developed using dexamethasone and E. bovis challenge. In this model, an oral challenge of at least 500,000 sporulated E. bovis oocysts in addition to dexamethasone injection at 7 days post challenge increased subsequent FOC. Further investigation of the immune response to E. bovis challenge during times of stress indicates that stress-induced suppression of cell mediated immunity and E. bovis challenge are required to increase subsequent oocyst shedding. These findings may represent the mechanism associated with stress-induced outbreaks of coccidiosis reported to occur in beef cattle in the United States. / Ph. D.

Weaning is defined as the physical separation of the cow-calf pair and the end of milk feeding. Natural weaning occurs between 7 and 14 months and is a gradual process. However, domestic weaning occurs between 6 and 8 months and occurs rapidly. Calves that are abruptly separated from their dam respond with increased vocalization and walking, and decreased eating and resting. The psychological stress the calf undergoes during weaning causes elevated glucocorticoid and catecholamine hormone concentrations that may predispose to increased morbidity and/or mortality from infectious diseases such as Bovine Respiratory Disease Complex. As an attempt to counter these changes, alternative weaning methods have been implemented and normally occur in two stages. Two-stage weaning begins with the cessation of milk feeding for approximately one week with the calf maintaining some contact with their dam and then permanent separation occurs. One of these methods uses a single fence to separate the cow-calf pair; this process allows the calf to see, hear and smell their dam, but does not allow the calf to suckle from its dam. Increases in cortisol, a glucocorticoid, have been linked to immunological alterations. Most notably, elevated cortisol concentrations decrease neutrophil function by down regulating the gene expression of CD62L and Fas. Cortisol also alters lymphocyte phenotype by decreasing ?δ T cells and increasing°? T cells in the circulation. Lastly, increases in cortisol can modify T cell cytokine production. The cytokines IL-12 and IFN? are secreted from T helper 1 cells while T helper 2 cells secrete IL-4 and IL-10; these T cells subsets also inhibit one another. During higher cortisol concentrations, these T cells are biased toward T helper 2 cytokine production. All these changes in immune function can lead to increased susceptibility to disease around the time of weaning. Therefore, two trials were conducted to test the hypotheses that abrupt weaning results in elevated concentrations of cortisol and subsequently alters immunological functions, and that fenceline weaning alleviates the increase in cortisol and alterations to immune function associated with weaning. In the fall of 2008, 12 Angus and Angus-X heifers (186°21 kgs; 174°16 days of age) were blocked by age and weight and randomly allotted into two groups, fenceline and abrupt. Blood samples were taken on day -7, 0, 7, 14, 21, and 42; fecal samples were taken on day -7, 0, and 3. All calves were weighed on day -7, 0, 7, 14, and 42. On day -1 all calves were separated from their dam and transported for 2 hours to another facility. On day 0 all calves were vaccinated with Brucella abortus (strain RB51). Serum was analyzed for IFN? and IL-4 as well as IgG1 and IgG2 specific antibodies to RB51. Fecal samples were analyzed for cortisol metabolites. Both IgG1 and IgG2 antibodies to RB51 increased from day 0 to day 14 (P<0.05), however no differences were detected between treatment groups. Fecal cortisol metabolites were higher on day 0 in abruptly weaned calves (P< 0.001) but did not differ between groups on day -7 or day 3. Fenceline calves had higher concentrations of IFN? in the serum on day -7 and day 0 as compared to the abruptly weaned calves (P<0.04). In the fall of 2009, forty-four Angus and Angus-X calves (19 heifers and 25 steers; 181°27 kgs; 148°17 days old) were blocked by age and gender and randomly allotted within block into two treatment groups, fenceline (FL) and abrupt (AB). Approximately half the fenceline calves were separated from their dams by a single fence at day -7 and the rest of the fenceline group at day -6; all calves were removed from their dam at day 0. Calves were vaccinated with Histophilus somni on day 1. Blood samples were taken at day -6, 1, 3, 8, 15, and 22. Fecal samples were taken on day -7, -6, 1 and 3. All calves were weighed on day -7, 0, 8, and 22. Serum samples were analyzed for IgG1 and IgG2 specific-H. somni antibodies, white blood cells were analyzed for lymphocyte phenotypes, and gene expression using 18S as the housekeeper gene. Fecal samples were analyzed for cortisol metabolites. Abruptly weaned calves had higher concentrations of cortisol metabolites in the feces than fenceline calves at day 1 (P<0.0001). No difference in average daily gain or H. somni specific antibodies between treatment groups was detected. There was a treatment*date interaction in lymphocyte and neutrophil populations (P<0.05); neutrophils from fenceline calves dropped from day -6 to day 1, but increased from day 1 to day 3, while abrupt calves decreased from day -6 to day 3. Lymphocytes from fenceline calves increased from day -6 to day 1, but decreased from day 1 to day 3, while lymphocytes from abrupt calves increased from day -6 to day 3. No difference in treatment groups was detected for lymphocyte phenotypes or gene expression; however, a date effect was detected. The CD4 and CD8 cell populations increased over time (P<0.0001) and WC1 and TcR1 decreased over time (P=0.0243 and P=0.0027 respectively) for both treatment groups. A decrease was detected over time for expression of GAPDH and CD62L (P<0.0001). The gene expression for the cytokines IFN?, IL-4 and IL-10 had no change over time. Results from the two studies suggest that fenceline weaning decreases the cortisol response associated with cow-calf separation, but does not have a significant effect on immunological parameters measured in this study. / Master of Science

Les cytokines jouent un rôle fondamental dans la régulation des processus biologiques via la cascade de signalisation JAK-STAT. Les « Suppressors of Cytokine Signalling » (SOCS), protéines intracellulaires, inhibent la voie JAK-STAT. Plusieurs études supportent leur implication dans des maladies immunitaires, mais peu d’informations sont disponibles sur leur expression par les lymphocytes T humains. Nous postulons que les cytokines Interféron-β(IFN-β) et Interleukine-27 (IL-27), dotées d’un potentiel immuno-régulateur, ont des rôles bénéfiques via l’induction des SOCS. L’impact de l’IFN-β et l’IL-27 sur l’expression des SOCS-1 et SOCS-3 par des cellules T CD8 et CD4 humaines a été étudié en utilisant des cellules sanguines de donneurs sains. L’expression de ces régulateurs a été évaluée aux niveaux de l’ARNm par qRT-PCR et protéique par immunocytochimie. Les SOCS-1 et SOCS-3 ont été rapidement induits en ARNm dans les deux types cellulaires en réponse à l’IFN-β ou l’IL-27 et une augmentation de l’expression a été confirmée au niveau protéique. Afin de mimer les thérapies à base d’IFN-β, les cellules T ont été exposées chroniquement à l’IFN-β. Après chaque ajout de cytokine les cellules T ont augmenté l’expression du SOCS-1, sans moduler le SOCS-3. L’IL-27 a induit les SOCS-1 et SOCS-3 préférentiellement dans les cellules T CD8 ; ceci corrèle avec des résultats du laboratoire démontrant une plus petite expression des récepteurs à l’IL-27 par les lymphocytes T CD4 que les CD8. Notre projet a permis d’élucider l’expression des SOCS dans deux populations de cellules T et de clarifier les mécanismes d’actions de l’IFN-β et l’IL-27. / Cytokines regulate fundamental biological processes via the JAK-STAT signaling pathway. Suppressors of Cytokine Signaling proteins (SOCS), intracellular proteins, inhibit the JAK-STAT pathway. Emerging evidence supports the involvement of SOCS in diseases of the immune system but no data is available regarding their expression in human T cells. We postulate that the cytokines Interferon-β (IFN-β) and Interleukin-27 (IL-27), both potential immuno-regulators, have beneficial roles through the induction of SOCS proteins. The impact of IFN-β and IL-27 on the SOCS-1 and SOCS-3 expression by human CD4 and CD8 T cells was assessed using peripheral blood mononuclear cells from healthy donors. We evaluated the expression of SOCS-1 and SOCS-3 at the mRNA level by qRTPCR and at the protein level by immunocytochemistry. A rapid increase of SOCS-1 and SOCS-3 mRNA levels was observed upon cytokine addition, and such upregulation was confirmed at the protein level. To mimic patients under IFN-β treatment, both T cell subsets were chronically exposed to IFN-β. We observed an increase of SOCS-1 after each stimulation but not for SOCS-3. IL-27 stimulation increased SOCS-1 and SOCS-3 mRNA levels in CD8 T cells but only slightly in CD4 T cells; these observations correlate with previous observations in our laboratory showing less IL-27 receptors on CD4 T cells than CD8 counterparts. Our project determined the distinct expression of SOCS proteins in different human T cells subsets. This study could highlight the mechanism of action of cytokines such as IFN-β and IL-27.

Introdução: O Lúpus Eritematoso Sistêmico (LES) é uma doença autoimune multissistêmica de etiologia complexa que envolve fatores ambientais, genéticos e hormonais. É caracterizada pela produção de autoanticorpos e mediadores inflamatórios, ativação e proliferação de células T autorreativas e perda da autotolerância imunológica. Em pacientes com LES, a expressão do receptor primário de ativação CD69 é aumentada e a de células T supressoras/reguladoras (Treg) CD4+CD25+FoxP3+ é reduzida. O CD69 é essencial para ativação de células T CD4 autorreativas enquanto que as células Treg são importantes na manutenção da autotolerância. Desta forma, células T tem um papel central na patogênese do LES, mas os mecanismos implicados na falência da autotolerância ainda não são elucidados, destacando a importância de estudos em modelos experimentais da doença, como o de LES-induzido por pristane. Objetivo: Quantificar células T CD4+CD69+ ativadas e Treg CD4+CD25+FoxP3+ no sangue, baço e LP de camundongos Balb/c LESinduzido por pristane no sentido de avaliar a falência de autotolerância neste modelo. Métodos: Analisamos 84 camundongos Balb/c fêmeas: 52 receberam por via intraperitoneal uma dose única de 0,5 ml de pristane e 32 a mesma dose de salina. Amostras de sangue, baço e LP dos camundongos eutanasiados foram coletadas 90, 120, 180 e 300 (T90, T120, T180 e T300) dias após a inoculação de pristane ou salina. Células mononucleares do sangue periférico (CMSP), do LP (CMLP) e esplenócitos foram obtidos por lise das hemácias seguida de lavagens com RPMI medium 1640 e centrifugação, e posteriormente criopreservadas até a avaliação por citometria de fluxo usando o aparelho Guava EasyCyteTM HT (Millipore). Para esta etapa, as células foram descongeladas, lavadas com RPMI medium 1640 e incubadas com anticorpos monoclonais dirigidos contra CD3, CD4, CD25, CD28, CD69, CTLA-4, FoxP3, CD14 e Ly6C (BD PharmingenTM). Os resultados foram expressos como média ± DP e teste de Mann-Whitney foi utilizado para análises estatísticas, sendo p<0,05 considerado significante. Resultados: Comparados aos animais controles, animais com LES-induzido por pristane apresentaram aumento de células T CD4+CD69+ no sangue nos T90, T120 e T180 (p < 0,022, p=0,008 e p=0,010, respectivamente) e no baço no T120 (p=0,049), enquanto que, no LP, houve redução destas células nos T120, T180 e T300 (p=0,001, p=0,001 e p < 0,001, respectivamente). A porcentagem de células Treg CD4+CD25+FoxP3+ foi menor no sangue nos T90, T120 e T180 (p=0,018, p=0,012, p < 0,046, respectivamente), no baço, nos T120 e T180 (p=0,018 e p=0,013), e no LP nos T90 e T300 (p=0,008 e p=0,005). Conclusão: Aumento da expressão de células T CD4+CD69+ e redução da expressão de Treg CD4+CD25+FoxP3+ sugerem células T CD4 ativadas e perda da autotolerância periférica em camundongos com LES-induzido por pristane. Estas alterações são semelhantes às observadas no lúpus humano, de modo que demonstramos que este modelo também pode ser útil na avaliação de mecanismos de ativação celular, tolerância periférica desequilíbrio imune homeostático envolvidos no LES / Introduction: Systemic Lupus Erythematosus (SLE) is multisystemic autoimmune disease with complex etiology that involves environmental, genetic and hormonal factors. Is characterized by auto-antibodies and inflammatory mediators production, autoreactive T cells activation and proliferation and loss of immunogenic autotolerance. In patients with SLE, expression of CD69 activation primary receptor is increased and the CD4+CD25+FoxP3+ suppressor/regulatory T cell (Treg) is reduced. CD69 is essential for activation of autoreactive CD4 T cells while Treg cells are important in autotolerance maintenance. In this way, T cells have a central role in the pathogenesis of SLE however, the mechanisms implied in the autotolerance failure are still not elucidated, highlighting the importance of studies in this disease\'s experimental models, such as pristane-induced SLE. Objective: Quantify activated CD4+CD69+ T cells and CD4+CD25+FoxP3+ Treg in blood, spleen and peritoneal lavage (PL) of Balb/c mice with pristane-induced SLE in order to evaluate autotolerance failure in this model. Methods: 84 female Balb/c mice were analyzed: 52 received a single intraperitoneal 0,5 ml dose of pristane and 32 the same dose of saline. Euthanized mice samples of blood, spleen and peritoneal lavage were collected 90, 120, 180 and 300 (T90, T120, T180 and T300) days after inoculation of pristane or saline. Mononuclear cells from peripheral blood (PBMC), PL (PLMC) and splenocytes were obtained by lysis of erythrocytes followed by washings with RPMI medium 1640 and centrifugation, subsequently criopreserved until evaluation by flow cytometry using the appliance GuavaEasyCyteTM HT (Millipore). For this step, cells were unfrozen, washed with RPMI medium 1640 and incubated with monoclonal antibodies against CD3, CD4, CD25, CD28, CD69, CTLA-4, FoxP3, CD14 and Ly6C (BD PharmingenTM). The results were expressed as mean ± SD and Mann-Whitney 11 test was used for statistical analysis, being considered significant p < 0,05. Results: Compared to control animals, SLE pristane-induced animals presented increase of CD4+CD69+ T cells in blood on T90, T120 and T180 (p=0.022, p=0.008 and p=0.010, respectively) and in spleen on T120 (p=0.049), while, in PL, there was reduction of these cells on T120, T180 and T300 (p=0.001, p=0.001 and p < 0.001, respectively). The porcentage of Treg CD4+CD25+FoxP3+ was smaller in blood on T90, T120 and T180 (p=0.018, p=0.012 and p < 0.046, respectively), in spleen on T120 and T180 (p=0.018 and p=0.013), and in PL on T90 and T300 (p=0.008 and p=0.005). Conclusion: Increase of CD4+CD69+ T cell and reduction of CD4+CD25+FoxP3+ Treg expression suggests activated T CD4 cells and loss of peripheral autotolerance in pristane-induced SLE mice. These alterations are similar to observed in human lupus, in order we showed that this model can also be useful in evaluating the mechanisms of cellular activation, peripheral tolerance and homeostatic immune imbalance involved in the LES

Introdução: O Lúpus Eritematoso Sistêmico (LES) é uma doença autoimune multissistêmica de etiologia complexa que envolve fatores ambientais, genéticos e hormonais. É caracterizada pela produção de autoanticorpos e mediadores inflamatórios, ativação e proliferação de células T autorreativas e perda da autotolerância imunológica. Em pacientes com LES, a expressão do receptor primário de ativação CD69 é aumentada e a de células T supressoras/reguladoras (Treg) CD4+CD25+FoxP3+ é reduzida. O CD69 é essencial para ativação de células T CD4 autorreativas enquanto que as células Treg são importantes na manutenção da autotolerância. Desta forma, células T tem um papel central na patogênese do LES, mas os mecanismos implicados na falência da autotolerância ainda não são elucidados, destacando a importância de estudos em modelos experimentais da doença, como o de LES-induzido por pristane. Objetivo: Quantificar células T CD4+CD69+ ativadas e Treg CD4+CD25+FoxP3+ no sangue, baço e LP de camundongos Balb/c LESinduzido por pristane no sentido de avaliar a falência de autotolerância neste modelo. Métodos: Analisamos 84 camundongos Balb/c fêmeas: 52 receberam por via intraperitoneal uma dose única de 0,5 ml de pristane e 32 a mesma dose de salina. Amostras de sangue, baço e LP dos camundongos eutanasiados foram coletadas 90, 120, 180 e 300 (T90, T120, T180 e T300) dias após a inoculação de pristane ou salina. Células mononucleares do sangue periférico (CMSP), do LP (CMLP) e esplenócitos foram obtidos por lise das hemácias seguida de lavagens com RPMI medium 1640 e centrifugação, e posteriormente criopreservadas até a avaliação por citometria de fluxo usando o aparelho Guava EasyCyteTM HT (Millipore). Para esta etapa, as células foram descongeladas, lavadas com RPMI medium 1640 e incubadas com anticorpos monoclonais dirigidos contra CD3, CD4, CD25, CD28, CD69, CTLA-4, FoxP3, CD14 e Ly6C (BD PharmingenTM). Os resultados foram expressos como média ± DP e teste de Mann-Whitney foi utilizado para análises estatísticas, sendo p<0,05 considerado significante. Resultados: Comparados aos animais controles, animais com LES-induzido por pristane apresentaram aumento de células T CD4+CD69+ no sangue nos T90, T120 e T180 (p < 0,022, p=0,008 e p=0,010, respectivamente) e no baço no T120 (p=0,049), enquanto que, no LP, houve redução destas células nos T120, T180 e T300 (p=0,001, p=0,001 e p < 0,001, respectivamente). A porcentagem de células Treg CD4+CD25+FoxP3+ foi menor no sangue nos T90, T120 e T180 (p=0,018, p=0,012, p < 0,046, respectivamente), no baço, nos T120 e T180 (p=0,018 e p=0,013), e no LP nos T90 e T300 (p=0,008 e p=0,005). Conclusão: Aumento da expressão de células T CD4+CD69+ e redução da expressão de Treg CD4+CD25+FoxP3+ sugerem células T CD4 ativadas e perda da autotolerância periférica em camundongos com LES-induzido por pristane. Estas alterações são semelhantes às observadas no lúpus humano, de modo que demonstramos que este modelo também pode ser útil na avaliação de mecanismos de ativação celular, tolerância periférica desequilíbrio imune homeostático envolvidos no LES / Introduction: Systemic Lupus Erythematosus (SLE) is multisystemic autoimmune disease with complex etiology that involves environmental, genetic and hormonal factors. Is characterized by auto-antibodies and inflammatory mediators production, autoreactive T cells activation and proliferation and loss of immunogenic autotolerance. In patients with SLE, expression of CD69 activation primary receptor is increased and the CD4+CD25+FoxP3+ suppressor/regulatory T cell (Treg) is reduced. CD69 is essential for activation of autoreactive CD4 T cells while Treg cells are important in autotolerance maintenance. In this way, T cells have a central role in the pathogenesis of SLE however, the mechanisms implied in the autotolerance failure are still not elucidated, highlighting the importance of studies in this disease\'s experimental models, such as pristane-induced SLE. Objective: Quantify activated CD4+CD69+ T cells and CD4+CD25+FoxP3+ Treg in blood, spleen and peritoneal lavage (PL) of Balb/c mice with pristane-induced SLE in order to evaluate autotolerance failure in this model. Methods: 84 female Balb/c mice were analyzed: 52 received a single intraperitoneal 0,5 ml dose of pristane and 32 the same dose of saline. Euthanized mice samples of blood, spleen and peritoneal lavage were collected 90, 120, 180 and 300 (T90, T120, T180 and T300) days after inoculation of pristane or saline. Mononuclear cells from peripheral blood (PBMC), PL (PLMC) and splenocytes were obtained by lysis of erythrocytes followed by washings with RPMI medium 1640 and centrifugation, subsequently criopreserved until evaluation by flow cytometry using the appliance GuavaEasyCyteTM HT (Millipore). For this step, cells were unfrozen, washed with RPMI medium 1640 and incubated with monoclonal antibodies against CD3, CD4, CD25, CD28, CD69, CTLA-4, FoxP3, CD14 and Ly6C (BD PharmingenTM). The results were expressed as mean ± SD and Mann-Whitney 11 test was used for statistical analysis, being considered significant p < 0,05. Results: Compared to control animals, SLE pristane-induced animals presented increase of CD4+CD69+ T cells in blood on T90, T120 and T180 (p=0.022, p=0.008 and p=0.010, respectively) and in spleen on T120 (p=0.049), while, in PL, there was reduction of these cells on T120, T180 and T300 (p=0.001, p=0.001 and p < 0.001, respectively). The porcentage of Treg CD4+CD25+FoxP3+ was smaller in blood on T90, T120 and T180 (p=0.018, p=0.012 and p < 0.046, respectively), in spleen on T120 and T180 (p=0.018 and p=0.013), and in PL on T90 and T300 (p=0.008 and p=0.005). Conclusion: Increase of CD4+CD69+ T cell and reduction of CD4+CD25+FoxP3+ Treg expression suggests activated T CD4 cells and loss of peripheral autotolerance in pristane-induced SLE mice. These alterations are similar to observed in human lupus, in order we showed that this model can also be useful in evaluating the mechanisms of cellular activation, peripheral tolerance and homeostatic immune imbalance involved in the LES