913 resultados para FoxP3, Galectin-10, autoimmunity, tolerance, CD4 CD25 regulatory T cells
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Nutritional status is an important determinant to the response against Leishmania infection, although few studies have characterized the molecular basis for the association found between malnutrition and the disease. Vitamin A supplementation has long been used in developing countries to prevent mortality by diarrheal and respiratory diseases, but there are no studies on the role of vitamin A in Leishmania infection, although we and others have found vitamin A deficiency in visceral Leishmaniasis (VL). Regulatory T cells are induced in vitro by vitamin A metabolites and are considered important cells implicated T CD4+ cell suppression in human VL. This work aimed to examine the correlation of nutritional status and the effect of vitamin A in the response against Leishmania infantum infection. A total of 179 children were studied: 31 had active VL, 33 VL history, 44 were DTH+ and 71 were DTH- and had negative antibody to Leishmania (DTH-/Ac-). Peripheral blood monuclear cells were isolated in a subgroup of 10 active VL and 16 DTH-/Ac- children and cultivated for 20h under 5 different conditions: 1) Medium, 2) Soluble promastigote L. infantum antigens (SLA), 3) All-trans retinoic acid (ATRA), 4) SLA + ATRA and 5) Concanavalin A. T CD4+CD25highFoxp3+, T CD4+CD25-Foxp3- and CD14+ monocytes were stained and studied by flow cytometry for IL-10, TGF-β and IL-17 production. Nutritional status was compromised in VL children, which presented lower BMI/Age and retinol concentrations when compared to healthy controls. We found a negative correlation between nutritional status (measured by BMI/Age and serum retinol) and anti-Leishmania antibodies and acute phase proteins. There was no correlation between nutritional status and parasite load. ATRA presented a dual effect in Treg cells and monocytes: In healthy children (DTH-/Ac-), it induced a regulatory response, increasing IL-10 and TGF-β production; in VL children it modulated the immune response, preventing increased IL-10 production after SLA stimulation. Furthermore, we found a positive correlation between BMI/Age and IL-17 production and negative correlation between serum retinol and IL-10 and TGF-β production in T CD4+CD25highFoxp3+ cells after SLA stimulus. Our results show a potential dual role of vitamin A in the immune system: improvement of regulatory profile during homeostasis and down modulation of IL-10 in Treg cells and monocytes during symptomatic VL. Therefore, the use of vitamin A concomitant to VL therapy might improve recovery from disease status in Leishmania infantum infection
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La maladie du greffon contre lhte (GVHD) est la principale cause de mortalit et de morbidit suite aux greffes de cellules souches hmatopotiques. Plusieurs patients demeurent rfractaires aux traitements actuels ce qui rend ncessaire le dveloppement de nouvelles stratgies afin de combattre cette maladie. Dans ltude qui suit, nous avons utilis un nouvel agent thrapeutique, le TH9402, une molcule photosensible et dmontr quelle permet, lorsquexpose la lumire visible (514 nm), dliminer slectivement les cellules T actives in vivo tout en prservant les cellules T au repos et les cellules T rgulatrices (Tregs). Les Tregs ainsi prservs peuvent abroger la rponse alloractive par la scrtion dIL-10 ou par contact cellule-cellule via un mcanisme impliquant le CTLA-4. Nous avons dcouvert que la signalisation du CTLA-4 tait associe une hausse de la population Treg in vitro. Cette hausse est due la conversion de cellules T CD4+CD25- en Tregs et non une prolifration slective des Tregs. Dans la deuxime partie de cette tude, nous avons dmontr que la signalisation de CTLA-4 tait associe une augmentation de lexpression de la protine Indoleamine 2,3 dioxygenase (IDO). Ces effets ncessitent la dpltion du tryptophane ainsi que de la protine de phase aigue GCN2. Finalement, nous avons observ que linfusion de cellules traites au TH9402 chez des patients souffrant de GVHD chronique est associe une augmentation de la population Treg chez ces patients sans causer de lymphopnie ni de diminution de la rponse immunitaire dirige contre les antignes viraux. Ces rsultats suggrent que le traitement au TH9402 pourrait reprsenter une approche particulirement intressante pour le traitement de la GVHD chronique rfractaire aux traitements actuels. De plus, laugmentation de lexpression dIDO pourrait tre utilise comme valeur prdictive de la rponse du patient au traitement. Ceci pourrait permettre damliorer la qualit de soins ainsi que de la qualit de vie des patients souffrant de GVHD chronique.
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Foxp3 es un marcador clave para identificacin y funcin clulas T reguladoras, adems su expresin se ha observado en diferentes lneas celulares de cncer. El objetivo de este estudio fue determinar si la expresin de Foxp3 en clulas de melanoma murino acta como un mecanismo de evasin de la respuesta inmune tumoral, modificando citocinas involucradas en la fase de inmunoedicin de cncer y promoviendo la generacin de clulas Treg. En este estudio se determin por primera vez la expresin de Foxp3 en las clulas melanoma murino B16F10 wt, y diseamos RNA de interferencia en contra de Foxp3, adems de analizar la expresin de CD25 y produccin de IL-2, INF-, TGF- e IL-10 para determinar su papel in vitro. Para la evaluacin del efecto de Foxp3 durante el desarrollo tumoral in vivo, se estableci una lnea celular con silenciamiento de Foxp3 la cul identificamos como B16F10.DMH1 y se montaron dos modelos de melanoma murino, uno inducido con clulas B16F10 wt y otro inducido con clulas B16F10.DMH1, y se analiz progresin tumoral, produccin de citocinas, expresin de CD25, Foxp3 y poblaciones celulares CD4+ , CD4+CD25+ y CD4+CD25+ Foxp3+ en TILs y clulas de bazo. Nuestros resultados in vitro demuestran que las clulas B16F10 wt expresan Foxp3 a nivel de RNAm y protena, y su localizacin celular es principalmente perinuclear, adems se encontr que estas clulas expresan CD25, y una produccin de citocinas del tipo INF-, TGF-, IL-10 e IL-2. Se encontr que la expresin de Foxp3 afecta la proliferacin en clulas B16F10, encontrando una correlacin positiva entre la expresin de Foxp3, CD25 e IL-2. In vivo, el silenciamiento de Foxp3 en las clulas B16F10.DMH1 afect el desarrollo del melanoma incrementando el tiempo de aparicin de tumor, sobrevida y disminuyendo el peso de los tumores, encontrando una correlacin positiva entre Foxp3, CD25, IL-2 e IL-10 y negativa con la produccin de IFN-, adems se determin que Foxp3 intratumoral est correlacionado con la expresin y presencia de clulas Treg con fenotipo CD4+CD25+ Foxp3+ en el microambiente tumoral y con una disminucin de clulas T CD4+ a nivel perifrico, sin afectar a linfocitos T activados (CD4+CD25+ ). Estos datos sugieren que Foxp3, participa en el desarrollo de la tumorognesis en melanoma murino in vitro e in vivo, con la capacidad de modular a citocinas, molculas involucradas en el desarrollo tumoral, as como poblaciones celulares con fenotipo regulador en el tumor, pero no en periferia.
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Adjuvants are substances that boost the protective immune response to vaccine antigens. The majority of known adjuvants have been identified through the use of empirical approaches. Our aim was to identify novel adjuvants with well-defined cellular and molecular mechanisms by combining a knowledge of immunoregulatory mechanisms with an in silico approach. CD4 + CD25 + FoxP3 + regulatory T cells (Tregs) inhibit the protective immune responses to vaccines by suppressing the activation of antigen presenting cells such as dendritic cells (DCs). In this chapter, we describe the identification and functional validation of small molecule antagonists to CCR4, a chemokine receptor expressed on Tregs. The CCR4 binds the chemokines CCL22 and CCL17 that are produced in large amounts by activated innate cells including DCs. In silico identified small molecule CCR4 antagonists inhibited the migration of Tregs both in vitro and in vivo and when combined with vaccine antigens, significantly enhanced protective immune responses in experimental models.
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Type 1 diabetes (T1D) is considered to be an autoimmune disease. The cause of T1D is the destruction of insulin-producing -cells in the pancreatic islets. The autoimmune nature of T1D is characterized by the presence of autoreactive T-cells and autoantibodies against -cell molecules. Insulin is the only -cell-specific autoantigen associated with T1D but the insulin autoantibodies (IAAs) are difficult to measure with proper sensitivity. T-cell assays for detection of autoreactive T-cells, such as insulin-specific T-cells, have also proven to be difficult to perform. The genetic risk of T1D is associated with the HLA gene region but the environmental factors also play an important role. The most studied environmental risk factors of T1D are enteroviruses and cow's milk which both affect the immune system through the gut. One hypothesis is that the insulin-specific immune response develops against bovine insulin in cow's milk during early infancy and later spreads to include human insulin. The aims of this study were to determine whether the separation of immunoglobulin (Ig)G from plasma would improve the sensitivity of the IAA assay and how insulin treatment affects the cellular immune response to insulin in newly diagnosed patients. Furthermore, the effect of insulin concentration in mother's breast milk on the development of antibodies to dietary insulin in the child was examined. Small intestinal biopsies were also obtained from children with T1D to characterize any immunological changes associated with T1D in the gut. The isolation of the IgG fraction from the plasma of T1D patients negative for plasma IAA led to detectable IAA levels that exceeded those in the control children. Thus the isolation of IgG may improve the sensitivity of the IAA assay. The effect of insulin treatment on insulin-specific T-cells was studied by culturing peripheral blood mononuclear cells with insulin. The insulin stimulation induced increased expression of regulatory T-cell markers, such as Foxp3, in those patients treated with insulin than in patients examined before initiating insulin treatment. This finding suggests that insulin treatment in patients with T1D stimulates regulatory T-cells in vivo and this may partly explain the difficulties in measuring autoantigen-specific T-cell responses in recently diagnosed patients. The stimulation of regulatory T-cells by insulin treatment may also explain the remission period often seen after initiating insulin treatment. In the third study we showed that insulin concentration in mother's breast milk correlates inversely with the levels of bovine insulin-specific antibodies in those infants who were exposed to cow's milk proteins in their diet, suggesting that human insulin in breast milk induces tolerance to dietary bovine insulin. However, in infants who later developed T1D-associated autoantibodies, the insulin concentration in their mother's breast milk was increased. This finding may indicate that in those children prone to -cell autoimmunity, breast milk insulin does not promote tolerance to insulin. In the small intestinal biopsies the presence of several immunological markers were quantified with the RT-PCR. From these markers the expression of the interleukin (IL)-18 cytokine was significantly increased in the gut in patients with T1D compared with children with celiac disease or control children. The increased IL-18 expression lends further support for the hypothesis that the gut immune system is involved in the pathogenesis of T1D.
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Background: The fecal neutrophil-derived proteins calprotectin and lactoferrin have proven useful surrogate markers of intestinal inflammation. The aim of this study was to compare fecal calprotectin and lactoferrin concentrations to clinically, endoscopically, and histologically assessed Crohns disease (CD) activity, and to explore the suitability of these proteins as surrogate markers of mucosal healing during anti-TNF therapy. Furthermore, we studied changes in the number and expression of effector and regulatory T cells in bowel biopsy specimens during anti-TNF therapy. Patients and methods: Adult CD patients referred for ileocolonoscopy (n=106 for 77 patients) for various reasons were recruited (Study I). Clinical disease activity was assessed with the Crohns disease activity index (CDAI) and endoscopic activity with both the Crohns disease index of severity (CDEIS) and the simple endoscopic score for Crohns disease (SES-CD). Stool samples for measurements of calprotectin and lactoferrin, and blood samples for CRP were collected. For Study II, biopsy specimens were obtained from the ileum and the colon for histologic activity scoring. In prospective Study III, after baseline ileocolonoscopy, 15 patients received induction with anti-TNF blocking agents and endoscopic, histologic, and fecal-marker responses to therapy were evaluated at 12 weeks. For detecting changes in the number and expression of effector and regulatory T cells, biopsy specimens were taken from the most severely diseased lesions in the ileum and the colon (Study IV). Results: Endoscopic scores correlated significantly with fecal calprotectin and lactoferrin (p<0.001). Both fecal markers were significantly lower in patients with endoscopically inactive than with active disease (p<0.001). In detecting endoscopically active disease, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for calprotectin 200 g/g were 70%, 92%, 94%, and 61%; for lactoferrin 10 g/g they were 66%, 92%, 94%, and 59%. Accordingly, the sensitivity, specificity, PPV, and NPV for CRP >5 mg/l were 48%, 91%, 91%, and 48%. Fecal markers were significantly higher in active colonic (both p<0.001) or ileocolonic (calprotectin p=0.028, lactoferrin p=0.004) than in ileal disease. In ileocolonic or colonic disease, colon histology score correlated significantly with fecal calprotectin (r=0.563) and lactoferrin (r=0.543). In patients receiving anti-TNF therapy, median fecal calprotectin decreased from 1173 g/g (range 88-15326) to 130 g/g (13-1419) and lactoferrin from 105.0 g/g (4.2-1258.9) to 2.7 g/g (0.0-228.5), both p=0.001. The relation of ileal IL-17+ cells to CD4+ cells decreased significantly during anti-TNF treatment (p=0.047). The relation of IL-17+ cells to Foxp3+ cells was higher in the patients baseline specimens than in their post-treatment specimens (p=0.038). Conclusions: For evaluation of CD activity, based on endoscopic findings, more sensitive surrogate markers than CDAI and CRP were fecal calprotectin and lactoferrin. Fecal calprotectin and lactoferrin were significantly higher in endoscopically active disease than in endoscopic remission. In both ileocolonic and colonic disease, fecal markers correlated closely with histologic disease activity. In CD, these neutrophil-derived proteins thus seem to be useful surrogate markers of endoscopic activity. During anti-TNF therapy, fecal calprotectin and lactoferrin decreased significantly. The anti-TNF treatment was also reflected in a decreased IL-17/Foxp3 cell ratio, which may indicate improved balance between effector and regulatory T cells with treatment.
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Type 1 diabetes (T1D) is considered to be an autoimmune disease. In T1D insulin producing pancreatic cells are destroyed. The disease process begins years before the clinical diagnosis of T1D. During the pathogenesis of T1D, pancreatic islets are infiltrated by cells of the immune system and T-lymphocytes are considered to be the main mediators of the -cell destruction. In children with an active -cell destruction process, autoantibodies against -cell antigens appear in the blood. Individuals at increased risk of developing T1D can often be identified by detecting serum autoantibodies against -cell antigens. Immunological aberrancies associated with T1D are related to defects in the polarization of T cells and in the function of regulatory mechanisms. T1D has been considered as an organ-specific autoimmune disease mediated by uncontrolled Th1-responses. In human T1D, the evidence for the role of over-expression of cytokines promoting cytotoxicity is controversial. For the past 15 years, regulatory T cells (Tregs) have been recognized as having a key role in the initiation and maintenance of tolerance, limiting harmful autoantigen-specific inflammation processes. It is possible that, if regulatory mechanisms fail to be initiated, the subtle inflammation targeting cells lead to insulitis and eventually to overt T1D in some individuals. In the present thesis, we studied the induction of Tregs during the generation of T-cell responses in T1D. The results suggest that the generation of regulatory mechanisms and effector mechanisms upon T-cell activation is aberrant in children with T1D. In our studies, an in vitro cytotoxic environment inhibited the induction of genes associated with regulatory functions upon T-cell activation. We also found T1D patients to have an impaired cytotoxic response against coxsackievirus B4. Ineffective virus clearance may increase the apoptosis of cells, and thus the risk of -cell specific autoimmunity, due to the increased presentation of -cell-derived peptides by APCs to T cells in pancreatic lymph nodes. Recently, a novel T helper cell subset called Th17 has been discovered. Animal models have associated Th17 cells and especially co-producers of IL-17 and IFN- with the pathogenesis of T1D. We aimed to characterize the role of Th17 immunity in human T1D. We demonstrated IL-17 activation to be a major alteration in T1D patients in comparison to healthy children. Moreover, alterations related to the FOXP3-mediated regulatory mechanisms were associated with the IL-17 up-regulation seen in T1D patients. These findings may have therapeutic implications for the treatment and prevention of T1D.
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Mycobacterium tuberculosis is the etiologic agent of human tuberculosis and is estimated to infect one-third of the world's population. Control of M. tuberculosis requires T cells and macrophages. T-cell function is modulated by the cytokine environment, which in mycobacterial infection is a balance of proinflammatory (interleukin-1 [IL-1], IL-6, IL-8, IL-12, and tumor necrosis factor alpha) and inhibitory (IL-10 and transforming growth factor beta [TGF-beta]) cytokines. IL-10 and TGF-beta are produced by M. tuberculosis-infected macrophages. The effect of IL-10 and TGF-beta on M. tuberculosis-reactive human CD4(+) and gammadelta T cells, the two major human T-cell subsets activated by M. tuberculosis, was investigated. Both IL-10 and TGF-beta inhibited proliferation and gamma interferon production by CD4(+) and gammadelta T cells. IL-10 was a more potent inhibitor than TGF-beta for both T-cell subsets. Combinations of IL-10 and TGF-beta did not result in additive or synergistic inhibition. IL-10 inhibited gammadelta and CD4(+) T cells directly and inhibited monocyte antigen-presenting cell (APC) function for CD4(+) T cells and, to a lesser extent, for gammadelta T cells. TGF-beta inhibited both CD4(+) and gammadelta T cells directly and had little effect on APC function for gammadelta and CD4(+) T cells. IL-10 down-regulated major histocompatibility complex (MHC) class I, MHC class II, CD40, B7-1, and B7-2 expression on M. tuberculosis-infected monocytes to a greater extent than TGF-beta. Neither cytokine affected the uptake of M. tuberculosis by monocytes. Thus, IL-10 and TGF-beta both inhibited CD4(+) and gammadelta T cells but differed in the mechanism used to inhibit T-cell responses to M. tuberculosis.
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Activation of CD4+ T cells results in rapid proliferation and differentiation into effector and regulatory subsets. CD4+ effector T cell (Teff) (Th1 and Th17) and Treg subsets are metabolically distinct, yet the specific metabolic differences that modify T cell populations are uncertain. Here, we evaluated CD4+ T cell populations in murine models and determined that inflammatory Teffs maintain high expression of glycolytic genes and rely on high glycolytic rates, while Tregs are oxidative and require mitochondrial electron transport to proliferate, differentiate, and survive. Metabolic profiling revealed that pyruvate dehydrogenase (PDH) is a key bifurcation point between T cell glycolytic and oxidative metabolism. PDH function is inhibited by PDH kinases (PDHKs). PDHK1 was expressed in Th17 cells, but not Th1 cells, and at low levels in Tregs, and inhibition or knockdown of PDHK1 selectively suppressed Th17 cells and increased Tregs. This alteration in the CD4+ T cell populations was mediated in part through ROS, as N-acetyl cysteine (NAC) treatment restored Th17 cell generation. Moreover, inhibition of PDHK1 modulated immunity and protected animals against experimental autoimmune encephalomyelitis, decreasing Th17 cells and increasing Tregs. Together, these data show that CD4+ subsets utilize and require distinct metabolic programs that can be targeted to control specific T cell populations in autoimmune and inflammatory diseases.
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Infant CD4+ T-cell responses to bacterial infections or vaccines have been extensively studied, whereas studies on CD8 + T-cell responses focused mainly on viral and intracellular parasite infections. Here we investigated CD8 + T-cell responses upon Bordetella pertussis infection in infants, children, and adults and pertussis vaccination in infants. Filamentous hemagglutinin-specific IFN- secretion by circulating lymphocytes was blocked by anti-MHC-I or -MHC-II antibodies, suggesting that CD4 + and CD8 + T lymphocytes are involved in IFN- production. Flow cytometry analyses confirmed that both cell types synthesized antigen-specific IFN-, although CD4 + lymphocytes were the major source of this cytokine. IFN- synthesis by CD8 + cells was CD4 + T cell dependent, as evidenced by selective depletion experiments. Furthermore, IFN- synthesis by CD4 + cells was sometimes inhibited by CD8 + lymphocytes, suggesting the presence of CD8 + regulatory T cells. The role of this dual IFN- secretion by CD4 + and CD8 + T lymphocytes in pertussis remains to be investigated. 2012 Violette Dirix et al.
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SUMMARY : Detailed knowledge of the different components of the immune system is required for the development of new immunotherapeutic strategies. CD4 T lymphocytes represent a highly heterogeneous group of cells characterized by various profiles of cytokine production and effector vs. regulatory functions. They are central players in orchestrating adaptive immune responses: unbalances between the different subtypes can lead either to aggressive autoimmune disorders or can favour the uncontrolled growth of malignancies. In this study we focused on the characterization of human CD4 T cells in advanced stage melanoma patients as well as in patients affected by various forms of autoimmune inflammatory spondyloarthropathies. In melanoma patients we report that a population of FOXP3 CD4 T cells, known as regulatory T cells, is overrepresented in peripheral blood, and even more in tumor-infitrated lymph nodes as well as at tumor sites, as compared to healthy donors. In tumor-infiltrated lymph nodes, but not in normal lymph nodes or in peripheral blood, FOXP3 CD4 T cells feature a highly differentiated phenotype (CD45RA-CCR7+/-), which suggests for a recent encounter with their cognate antigen. FOXP3 CD4 T cells have been described to be an important component of the several known immune escape mechanisms. We demonstrated that FOXP3 CD4 T cells isolated from melanoma patients exert an in vitro suppressive action on autologous CD4 T cells, thus possibly inhibiting an efficient anti-tumor response. Next, we aimed to analyse CD4 T cells at antigen-specific level. In advanced stage melanoma patients, we identified for the first time, using pMHCII multimers, circulating CD4 T cells specific for the melanoma antigen Melan-A, presented by HLA-DQB1 *0602. Interestingly, in a cohort of melanoma patients enrolled in an immunotherapy trails consisting of injection of a Melan-A derived peptide, we did not observe signif cant variations in the ex vivo frequencies of Melan-A specific CD4 T cells, but important differences in the quality of the specific CD4 T cells. In fact, up to 50% of the ex vivo Melan-A/DQ6 specific CD4 T cells displayed a regulatory phenotype and were hypoproliferative before vaccination, while more effector, cytokine-secreting Melan-A/DQ6 specific CD4 T cells were observed after immunization. These observations suggest that peptide vaccination may favourably modify the balance between regulatory and effector tumor-specific CD4 T cells. Finally, we identified another subset of CD4 T cells as possible mediator of pathology in a group of human autoimmune spondyloarthropathies, namely Th17 cells. These cells were recently described to play a critical role in the pathogenesis of some marine models of autommunity. We document an elevated presence of circulating Th17 cells in two members of seronegative spondyloarthropathies, e.g. psoriatic arthritis and ankylosing spondylitis, while we do not observe increased frequencies of Th17 cells in peripheral blood of rheumatoid arthritic patients. In addition, Th17 cells with a more advanced differentiation state (CD45RA-CCR7-CD27-) and polyfunctionality (concomitant secretion of IL-17, IL-2 and TNF) were observed exclusively in patients with seronegative spondylarthropathies. Together, our observations emphasize the importance of CD4 T cells in various diseases and suggest that immunotherapeutic approaches considering CD4 T cells as targets should be evaluated in the future.
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Limportance respective des lymphocytes T rgulateurs naturels gnrs dans le thymus ou induits en priphrie dans la rgulation immunitaire et la rsolution de linflammation est dsormais bien tablie. Nous avons contribu mettre en vidence une nouvelle voie dinduction de lymphocytes T rgulateurs priphriques partir de cellules T humaines CD4+CD25- naves et mmoires. Nous avons montr que lengagement de la molcule ubiquitaire transmembranaire CD47 sur la cellule T par un anticorps monoclonal ou par le peptide 4N1K (peptide driv du domaine carboxy-terminal de la thrombospondine-1 et spcifique du site de liaison CD47) induisait des lymphocytes T CD4+ rgulateurs exerant une fonction suppressive sur les lymphocytes T effecteurs. Les proprits suppressives induites par la thrombospondine-1 confortent les fonctions anti-inflammatoires de cette protine de la matrice extracellulaire. Linhibition exerce par les lymphocytes T rgulateurs induits dpend du contact intercellulaire entre les cellules T rgulatrices et leurs cibles, et est indpendante du TGF-. Nos rsultats dmontrent galement le rle de CD47 sur le lymphocyte T CD4+ dans la rponse immunitaire spcifique de lantigne in vivo. En effet, les souris BALB/c dficientes pour CD47 prsentent un biais de la scrtion danticorps et de cytokines de type Th1, alors que les souris BALB/c sont dcrites comme exprimant un profil de production de cytokines de type Th2. Nos travaux mettent en vidence le rle de CD47 dans linhibition du dveloppement dune rponse cellulaire et humorale de type Th1 in vivo, confirmant de prcdentes tudes in vitro ralises avec des cellules T CD4+ humaines. Nous prsentons galement le rle inhibiteur de lengagement de CD28 in vitro sur la diffrenciation en cellules Th17 des lymphocytes T CD4+ nafs isols de souris BALB/c. Le mcanisme propos est dpendant de la production de lIL-2 et de lIFN- et indpendant de la prsence de lymphocytes T rgulateurs. Notre tude du rle de deux molcules transmembranaires CD47 et CD28 exprimes sur la cellule T CD4+, contribue une meilleure connaissance des mcanismes impliqus dans la tolrance immunologique, la rsolution de linflammation et la diffrenciation des cellules T "helper" CD4+.
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Limmunosuppression optimale aprs greffe dorgane solide est une balance dlicate et propre chaque individu entre le risque de rejet et les risques lis une surexposition au traitement immunosuppresseur. Lvaluation de la fonction rsiduelle des lymphocytes T aprs stimulation par un mitogne (pharmacodynamie effective) devrait permettre de mesurer leffet direct des mdicaments immunosuppresseurs sur leur cible. Nous avons tudi diffrents paramtres de pharmacodynamie effective chez 34 receveurs pdiatriques de greffe dorganes solides traits par tacrolimus et mycophnolate. Les tests proposs dans ce travail sont adapts au milieu pdiatrique et une ralisation en temps rel. La quantification du CD25 parmi les CD4 activs par lOKT3 permet de distinguer deux groupes de patients selon leur degr dimmunosuppression. Lge mdian est plus bas et la concentration plasmatique mdiane en MPA plus leve dans le groupe de patients plus fortement immunosupprims. Ltude des paramtres immunologiques pouvant influencer la rponse (scrtion des interleukines, proportion des sous-populations lymphocytaires CD4, CD8, T nafs et Trg) ainsi que ltude du pouvoir de restauration de la fonction lymphocytaire par lIl-2, la guanosine ou la xanthosine, ne permettent pas de mieux comprendre les variabilits interindividuelles observes. Ces rsultats devront tre confirms sur une cohorte plus grande de patients afin de juger de leur intrt en pratique clinique.
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Lhpatite auto-immune (HAI) est une maladie chronique caractrise par une destruction progressive du parenchyme hpatique par le systme immunitaire. La majorit des patients atteints dHAI sont des femmes (75% 90% des cas). Lamlioration des traitements au cours des dernires annes a permis un grand nombre de ces femmes de devenir enceintes. Pendant la grossesse, une rmission spontane de la maladie a pu tre observe chez les femmes atteintes dHAI. Cette rmission est temporaire et elle est gnralement suivie dune rechute suite laccouchement (post-partum). Les causes exactes de cette rmission associe la grossesse et de la rechute post-partum ne sont pas connues ce jour. Nous avons donc tent de reproduire ces phnomnes dans un modle murin dHAI dvelopp dans notre laboratoire, afin de dterminer les mcanismes possiblement impliqus. Notre modle dHAI consiste en une xno-immunisation de souris C57BL/6 avec les auto-antignes impliqus dans lHAI de type 2 chez lhumain. Nous avons ainsi accouples des souris pralablement xno-immunises, puis nous les avons sacrifies au dbut de la 3e semaine de gestation ou 2 3 semaines post-partum, afin dvaluer les dommages hpatiques et afin dtudier la rponse immunitaire. Comme chez les femmes atteintes dHAI, les souris prsentent une rmission de la maladie pendant la grossesse. Nous en sommes venus cette conclusion par lobservation dune diminution de linflammation hpatique, des niveaux de transaminases sriques et des titres dauto-anticorps circulants. linverse des humains, les souris xno-immunises ne prsentent pas de rechute post-partum. Une analyse des cellules rgulatrices (cellules T rgulatrices et cellules B productrices d'IL-10) suggre une implication des Tregs hpatiques dans la rmission, car ceux-ci sont augments pendant la gestation. Ces Tregs hpatiques sont majoritairement dorigine thymique et ne semblent pas particulirement attirs au foie en rponse linflammation. La polarisation TH2 est un phnomne connu pendant la grossesse, par contre elle ne semble pas influencer la rponse auto-immune dans nos souris. Une meilleure comprhension des mcanismes dimmunosuppression observs lors de la grossesse pourrait mener au dveloppement dune thrapie mieux cible.
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Sialostatin L (SialoL) is a secreted cysteine protease inhibitor identified in the salivary glands of the Lyme disease vector Ixodes scapularis. In this study, we reveal the mechanisms of SialoL immunomodulatory actions on the vertebrate host. LPS-induced maturation of dendritic cells from C57BL/6 mice was significantly reduced in the presence of SialoL. Although OVA degradation was not affected by the presence of SialoL in dendritic cell cultures, cathepsin S activity was partially inhibited, leading to an accumulation of a 10-kDa invariant chain intermediate in these cells. As a consequence, in vitro Ag-specific CD4(+) T cell proliferation was inhibited in a time-dependent manner by SialoL, and further studies engaging cathepsin S(-/-) or cathepsin L(-/-) dendritic cells confirmed that the immunomodulatory actions of SialoL are mediated by inhibition of cathepsin S. Moreover, mice treated with SialoL displayed decreased early T cell expansion and recall response upon antigenic stimulation. Finally, SialoL administration during the immunization phase of experimental autoimmune encephalomyelitis in mice significantly prevented disease symptoms, which was associated with impaired IFN-gamma and IL-17 production and specific T cell proliferation. These results illuminate the dual mechanism by which a human disease vector protein modulates vertebrate host immunity and reveals its potential in prevention of an autoimmune disease. The Journal of Immunology, 2009, 182: 7422-7429.
