933 resultados para Lymphocytes T CD4
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Although they are considered as antigen presenting cells (APC), the role of antigen-unspecific B-lymphocytes in antigen presentation and T lymphocyte stimulation remains controversial. In this paper, we tested the capacity of normal human peripheral activated B cells to stimulate T cells using melanoma antigens or melanoma cell lysates. B lymphocytes activated through CD40 ligation and then pulsed with tumor antigens efficiently processed and presented MHC class II restricted peptides to specific CD4+ T cell clones. This suggests that CD40-activated B cells have the functional and molecular competence to present MHC class II epitopes when pulsed with exogenous antigens, thereby making them a relevant source of APC to generate T cells. To test this hypothesis, CD40-activated B cells were pulsed with a lysate prepared from melanoma cells and used to stimulate peripheral autologous T cells. Interestingly, T cells specific to melanoma antigens were generated. Further analysis of these T cell clones revealed that they recognized MHC class II restricted epitopes from tyrosinase, a known melanoma tumor antigen. The efficient antigen presentation by antigen-unspecific activated B cells was correlated with a down-regulation in the expression of HLA-DO, a B cell specific protein known to interfere with HLA-DM function. Because HLA-DM is important in MHC class II peptide loading, the observed decrease in HLA-DO may partially explain the enhanced antigen presentation following B-cell activation. Results globally suggest that when they are properly activated, antigen-unspecific B-lymphocytes can present exogenous antigens by MHC class II molecules and stimulate peripheral antigen-specific T cells. Antigen presentation by activated B cells could be exploited for immunotherapy by allowing the in vitro generation of T cells specific against antigens expressed by tumors or viruses.
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Affiliation: Dpartement de microbiologie et immunologie, Facult de mdecine, Universit de Montral & Institut de Recherches Cliniques de Montral
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Les voies de signalisation des MAP kinases (MAPK) conventionnelles jouent des rles essentiels pendant le dveloppement des lymphocytes T (LT) ainsi que lors de leur activation suite la reconnaissance antignique. En raison de ses diffrences structurelles ainsi que de son mode de rgulation, ERK3 fait partie des MAPK dites non-conventionnelles. Encore aujourdhui, les vnements menant lactivation de ERK3, ses substrats ou partenaires ainsi que sa fonction physiologique demeurent peu caractriss. Nous avons entrepris dans cette thse dtudier le rle de ERK3 lors du dveloppement et de lactivation des LT en utilisant un modle de souris dficient pour lexpression de ERK3. Nous avons premirement tabli que ERK3 est exprime chez les thymocytes. Ensuite, nous avons valu le dveloppement thymique chez la souris ERK3-dficiente et nous avons observ une diminution significative de la cellularit aux tapes DN1, DP et SP CD4+ du dveloppement des LT. La cration de chimres hmatopotiques ERK3-dficientes nous a permis de dmontrer que la diminution du nombre de cellules observe aux tapes DN1 et DP est autonome aux thymocytes alors que le phnotype observ ltape SP CD4+ est dpendant de labolition simultane de ERK3 dans lpithlium thymique et dans les thymocytes. Une tude plus approfondie de ltape DP nous a permis de dmontrer quen absence de ERK3, les cellules DP meurent plus abondamment et accumulent des cassures doubles brins (DSB) dans leur ADN. De plus, nous avons dmontr que ces cassures dans lADN sont ralises par les enzymes RAG et quen absence de ces dernires, la cellularit thymique est presque rtablie chez la souris ERK3-dficiente. Ces rsultats suggrent que ERK3 est implique dans un mcanisme essentiel la rgulation des DSB pendant le rarrangement V(D)J de la chane du rcepteur des cellules T (RCT). Dans le deuxime article prsent dans cette thse, nous avons montr que ERK3 est exprim chez les LT priphriques, mais seulement suite leur activation via le RCT. Une fois activs in vitro les LT ERK3-dficients prsentent une diminution marque de leur prolifration et dans la production de cytokines. De plus, les LT ERK3-dficients survivent de faon quivalente aux LT normaux, mais tonnamment, ils expriment des niveaux plus faibles de la molcule anti-apoptotique Bcl-2. Ces rsultats suggrent que la prolifration rduite des LT ERK3-dficients est la consquence dune altration majeure de leur activation. Ainsi, nos rsultats tablissent que ERK3 est une MAPK qui joue des rles essentiels et uniques dans le dveloppement thymique et dans lactivation des lymphocytes T priphriques. Grce ces travaux, nous attribuons pour la toute premire fois une fonction in vivo pour ERK3 au cours de deux diffrentes tapes de la vie dun LT.
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Suite la rencontre dun antigne (Ag) prsent la surface des cellules prsentatrice de lAg (CPA), les lymphocytes T nafs, ayant un rcepteur des cellules T (RCT) spcifique de lAg, vont prolifrer et se diffrencier en LT effecteurs (1). Suite llimination de lAg la majorit des LTe vont mourir par apoptose alors que les restants vont se diffrencier en LT mmoire (LTm) protgeant lorganisme long terme. Les mcanismes qui permettent la diffrenciation des LTe en LTm sont encore inconnus. Pour comprendre comment les LTm CD8+ sont gnrs partir des LTe, nous avons mis lhypothse que la densit de lAg prsent par les CPA peut avoir un impact sur la slection des LT CD8+ rpondant lAg se diffrencier en LTm. De manire intressante, nos rsultats montrent quune immunisation avec des cellules dendritiques (DCs) exprimant un haut niveau de complexe CMH/peptide sa surface permet le dveloppement de LTm. linverse, le dveloppement des LTm est fortement rduit (10-20X) lorsque les souris sont immunises avec des DCs exprimant un niveau faible de complexes CMH/peptide leur surface. De plus, la quantit dAg na aucune influence ni sur lexpansion des LT CD8+ ni sur lacquisition de leurs fonctions effectrices, mais affecte de manire critique la gnration des LTm. Nos rsultats suggrent que le nombre de RCT engag lors de la reconnaissance de lAg est important pour la formation des LTm. Pour cela nous avons observ par vido-microscopie le temps dinteraction entre des LTn et des DCs. Nos rsultats montrent que le temps et la qualit de linteraction sont dpendants de la densit dAg prsent par les DCs. Effectivement, nous observons une diminution dans le pourcentage de LT faisant une interaction prolonge avec les DCs quand le niveau dAg est faible. De plus, nous observons des variations de lexpression des facteurs de transcription clefs impliqus dans la diffrenciation des LTm tels quEomes, Bcl-6 et Blimp-1. Par ailleurs, la densit dAg fait varier lexpression du Neuron-derived orphan nuclear receptor 1 (Nor-1). Nor-1 est impliqu dans la conversion de Bcl-2 en molcule pro-apoptotique et contribue la mort par apoptose des LTe pendant la phase de contraction. Notre modle propose que la densit de lpitope contrle la gnration des CD8+ LTm. Une meilleure comprhension des mcanismes impliqus dans la gnration des LTm permettra le dveloppement de meilleures stratgies pour la gnration de vaccin. Dans un second temps, nous avons valu le rle du signal RCT dans lhomostasie des LTm. Pour ce faire, nous avons utilis un modle de souris transgnique pour le RCT dont son expression peut tre module par un traitement la ttracycline. Ce systme nous a permis dabolir lexpression du RCT la surface des LTm. De manire intressante, en absence de RCT exprim, les LTm CD8+ peuvent survivre long terme dans lorganisme et rester fonctionnels. De plus, une sous population des LTm CD4+ a la capacit de survivre sans RCT exprim dans un hte lymphopnique alors que lautre sous population ncessite lexpression du RCT.
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Les chimiokines et leurs rcepteurs respectifs jouent un rle important dans limmunit inne et adaptative. Les rcepteurs de chimiokines identifient des cellules T CD4+ avec potentiel de migration dans des tissus spcifiques et fonctionnalit distincte du point de vue de la spcificit antignique et de la production de cytokines. Lidentit de la population des cellules T CD4+ susceptibles versus rsistantes linfection par le virus de limmunodficience humaine (VIH) reste mal dfinie. Le recrutement dans les muqueuses intestinales dun excs de cellules T effectrices (CD8+) compar aux cellules cibles (CD4+) reprsente un bon pronostic de linfection par le virus de limmunodficience simienne (VIS), tandis que la dpltion des cellules Th17 dans les tissus lymphodes associs au tractus gastro-intestinal (GALT) est un marqueur de la progression de linfection VIH. Leffet rgulateur des chimiokines sur lactivation de la rplication virale dans diffrentes sous-populations cellulaires T CD4+ reste peu tudi. Ce projet de matrise est divis en 3 parties: (1) lidentification des rcepteurs de chimiokines CCR4, CXCR3 et CCR6 comme marqueurs de surfaces des sous populations T CD4+ avec susceptibilit distincte linfection par le VIH; (2) la caractrisation phnotypique et fonctionnelle des cellules T CD4+ et T CD8+ spcifiques au VIH de sujets progression lente vers le stade sida (LTNP); et (3) les effets des chimiokines ligands de CCR4, CXCR3 et CCR6 sur lactivation cellulaire et la rplication virale in vitro. Nos rsultats dmontrent que les cellules T CD4+ CCR4+CCR6+ (profile cytokinique Th17) et CXCR3+CCR6+ (profile cytokinique Th1/Th17) sont hautement permissives linfection par le VIH. Nous proposons galement de nouveaux corrlats de protection immunitaire contre le VIH chez les sujets LTNP: (i) le potentiel de co-localisation dans les muqueuses intestinales des cellules T CD4+ et CD8+ spcifiques au VIH via lintgrine 7, (ii) le ratio lev entre les cellules T effectrices (CD8+) versus les cellules cibles (CD4+) spcifiques au VIH, (iii) le profil cytokinique Th17 et (iv) la capacit des cellules T CD4+ et CD8+ spcifiques au VIH produire des ligands de CCR5 bloquant lentre virale. Finalement, nos rsultats sur leffet co-stimulateur des chimiokines sur les cellules T et leurs effets opposs sur la rplication virale dmontrent limplication du rseau des chimiokines dans la rgulation de la pathogense de linfection VIH.
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Lymphocyte subsets, activation markers and apoptosis were assessed in 20 HIV-exposed noninfected (ENI) children born to HIV-infected women who were or not exposed to antiretroviral (ARV) drugs during pregnancy and early infancy. ENI children and adolescents were aged 6-18 years and they were compared to 25 age-matched healthy non-HIV-exposed children and adolescents (Control). ENI individuals presented lower CD4(+) T cells/mm(3) than Control group (control: 1120.3 vs. ENI: 876.3; t-test, p=0.030). ENI individuals had higher B-cell apoptosis than Control group (Control: 36.6%, ARV exposed: 82.3%, ARV nonexposed: 68.5%; Kruskal-Wallis, p < 0.05), but no statistical difference was noticed between those exposed and not exposed to ARV. Immune activation in CD4(+) T, CD8(+) T and in B cells was comparable in ENI and in Control children and adolescents. Subtle long-term immune alterations might persist among ENI individuals, but the clinical consequences if any are unknown, and these children require continued monitoring.
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Although regulation of CXCR3 and CCR4 is related to Th1 and Th2 differentiation, respectively, many CXCR3(+) and CCR4(+) cells do not express IFN-gamma and/or IL-4, suggesting that the chemokine receptor genes might be inducible by mechanisms that are lineage-independent. We investigated the regulation of CXCR3 versus IFNG, and CCR4 versus IL4 in human CD4(+) T cells by analyzing modifications of histone H3. In naive cord-blood cells, under nonpolarizing conditions not inducing IL4, CCR4 was induced to high levels without many of the activation-associated changes in promoter histone H3 found for both IL4 and CCR4 in Th2 cells. Importantly, CCR4 expression was stable in Th2 cells, but fell in nonpolarized cells after the cells were rested; this decline could be reversed by increasing histone acetylation using sodium butyrate. Patterns of histone H3 modifications in CXCR3(+) CCR4(-) and CXCR3(-) CCR4(+) CD4(+) T-cell subsets from adult blood matched those in cells cultured under polarizing conditions in vitro. Our data show that high-level lineage-independent induction of CCR4 can occur following T-cell activation without accessibility-associated changes in histone H3, but that without such changes expression is transient rather than persistent.
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Over the past 20 y, the hormone melatonin was found to be produced in extrapineal sites, including cells of the immune system. Despite the increasing data regarding the biological effects of melatonin on the regulation of the immune system, the effect of this molecule on T cell survival remains largely unknown. Activation-induced cell death plays a critical role in the maintenance of the homeostasis of the immune system by eliminating self-reactive or chronically stimulated T cells. Because activated T cells not only synthesize melatonin but also respond to it, we investigated whether melatonin could modulate activation-induced cell death. We found that melatonin protects human and murine CD4(+) T cells from apoptosis by inhibiting CD95 ligand mRNA and protein upregulation in response to TCR/CD3 stimulation. This inhibition is a result of the interference with calmodulin/calcineurin activation of NFAT that prevents the translocation of NFAT to the nucleus. Accordingly, melatonin has no effect on T cells transfected with a constitutively active form of NFAT capable of migrating to the nucleus and transactivating target genes in the absence of calcineurin activity. Our results revealed a novel biochemical pathway that regulates the expression of CD95 ligand and potentially other downstream targets of NFAT activation. The Journal of Immunology, 2010, 184: 3487-3494.
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Although CD8+ T cells do not contribute to protection against the blood stage of Plasmodium infection, there is mounting evidence that they are principal mediators of murine experimental cerebral malaria (ECM). At present, there is no direct evidence that the CD8+ T cells mediating ECM are parasite-specific or, for that matter, whether parasite-specific CD8+ T cells are generated in response to blood-stage infection. To resolve this and to define the cellular requirements for such priming, we generated transgenic P. berghei parasites expressing model T cell epitopes. This approach was necessary as MHC class I-restricted antigens to blood-stage infection have not been defined. Here, we show that blood-stage infection leads to parasite-specific CD8+ and CD4+ T cell responses. Furthermore, we show that P. berghei-expressed antigens are cross-presented by the CD8α+ subset of dendritic cells (DC), and that this induces pathogen-specific cytotoxic T lymphocytes (CTL) capable of lysing cells presenting antigens expressed by blood-stage parasites. Finally, using three different experimental approaches, we provide evidence that CTL specific for parasite-expressed antigens contribute to ECM. <br />
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Eradication of HIV-1 with highly active antiretroviral therapy (HAART) is not possible due to the persistence of long-lived, latently infected resting memory CD4+ T cells. We now show that HIV-1 latency can be established in resting CD4+ T cells infected with HIV-1 after exposure to ligands for CCR7 (CCL19), CXCR3 (CXCL9 and CXCL10), and CCR6 (CCL20) but not in unactivated CD4+ T cells. The mechanism did not involve cell activation or significant changes in gene expression, but was associated with rapid dephosphorylation of cofilin and changes in filamentous actin. Incubation with chemokine before infection led to efficient HIV-1 nuclear localization and integration and this was inhibited by the actin stabilizer jasplakinolide. We propose a unique pathway for establishment of latency by direct HIV-1 infection of resting CD4+ T cells during normal chemokine-directed recirculation of CD4+ T cells between blood and tissue. <br />
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The oral manifestations due to HIV infection are, a lot of times, the first clinical signs of the disease. These injuries may also function as beepers and sentries of the curse and progression of the HIV infection and AIDS. The objective of this work was to evaluate the prevalence of the oral injuries in HIV positive patients, relating them with the CD4+ cells counting and the viral load in patients from the Hospital of Infected contagious Gizelda Trigueiro in Natal-RN. One hundred and one patients were evaluated, where after the clinical exam of the oral cavity, these ones were conducted to the peripheral blood collection for the counting of CD4+ lymphocytes. We observed a prevalence of 25,6%, that is, 31 cases. The Oral Candidiasis was the most commum injure, followed by Oral Hairy Leukoplakia, linear gingival erytema, lips herpes, gingivitis and periodontitis - HIV. The average counting of cells CD4+ of the injury carrying patients was of 250 cells/mm3. We did not observe relation between the presence of injuries and the viral load of the individuals
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The expression of immune response in the form of leukocytic infiltrate by CD3+, CD4+, and CD8+ cells in the epithelium and in the intestinal lamina propria of chicks was studied in the present work by means of immunohistochemical reaction. The chicks were treated with Lactobacillus spp. or cecal microflora (CM) and experimentally challenged or not with Salmonella enterica serovar Enteritidis. The 320 birds utilized were divided into 4 groups containing 80 chicks each and submitted to treatments with Lactobacillus reuteri, Lactobacillus salivarius, Lactobacillus acidophilus, and CM. Each group was subdivided into 4 subgroups of 20 birds each and classified into a subgroup that did not receive treatment (negative control), subgroup treated, subgroup treated and challenged with Salmonella Enteritidis, and subgroup only challenged with Salmonella Enteritidis (positive control). The results obtained show that the treatment with L. reuteri, L. salivarius, L. acidophilus, or CM and challenged or not with Salmonella Enteritidis determine immune response in the form of leukocytic infiltrate by CD3+ and CD8+ lymphocytes followed by CD4+ in the epithelium and in the lamina propria of the duodenum, jejunum, and cecum of chicks up to 12 d of age. The quantity of CD3+ lymphocytes was significantly higher (P < 0.05) in the intestine of chicks treated with L. acidophilus or CM and challenged or not with Salmonella Enteritidis; however, the higher quantity of CD8+ lymphocytes was in the intestine of chicks treated with CM and challenged with Salmonella Enteritidis. The duodenum was the segment in which the immune response by T cells (CD3+, CD4+, and CD8+) was stimulated with the greatest intensity, followed by, respectively, the jejunum and cecum. The quantity of CD3+ lymphocytes present in the duodenum, jejunum, and cecum increases with the age of chicks, independent of the stimulus determined by treatments or challenge.
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Ps-graduao em Cincia Animal - FMVA
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Ps-graduao em Biocincias e Biotecnologia Aplicadas Farmcia - FCFAR
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Fundao de Amparo Pesquisa do Estado de So Paulo (FAPESP)
