921 resultados para Lymphocytes CD4 and CD8
Resumo:
L���infection par le VIH-1 est caract��ris��e par une d��pl��tion progressive des cellules T CD4+ ainsi que par un dysfonctionnement des cellules T qui, en l���absence de traitements anti-r��troviraux, conduit in��luctablement �� la progression de la maladie vers le stade SIDA. Certains des m��canismes impliqu��s dans ce dysfonctionnement de la r��ponse cellulaire T ont ��t�� ��lucid��s et ont r��v��l�� un r��le important de la mol��cule PD-1 dans l���exhaustion des cellules T en phase chronique de l���infection. En effet, des niveaux ��lev��s de PD-1 ont ��t�� associ��s �� une charge virale ��lev��e ainsi qu����� une diminution de la production de cytokines et de la capacit�� de prolif��rer des cellules T sp��cifiques du virus. De plus, bloquer in vitro l���interaction de PD-1 avec son ligand PD-L1 en utilisant un anticorps bloquant r��tabli la fonction de ces cellules. De fa��on int��ressante, notre groupe ainsi que d���autres ��quipes, ont montr�� que l���expression de PD-1 ��tait non seulement augment��e sur les cellules sp��cifiques de l���antig��ne mais aussi sur les cellules T totales. Cependant, peu de choses sont connues quant �� l���impact de l���expression de PD-1 sur le renouvellement et la diff��renciation des cellules T qui expriment PD-1, et ce au cours de l���infection. L���expression de PD-1 n���a notamment pas ��t�� ��tudi��e en phase aigue de l���infection. Nous montrons clairement que, aussi bien chez les individus en phase aigue qu���en phase chronique de l���infection, l���expression de PD-1 est augment��e sur toutes les sous-populations T, y compris les cellules na��ves. Nous avons ��galement mis en relief une distribution anormale des sous-populations T, ces cellules ayant un ph��notype plus diff��renci��, et ce �� tous les stades de la maladie. Dans cette th��se, nous discutons le r��le possible de PD-1 dans l���hom��ostasie des cellules T chez les individus infect��s par le VIH-1. En ��tudiant la transition de la phase aigue �� la phase chronique de l���infection, nous avons trouv�� que les sous-populations T CD8+ des individus r��cemment infect��s exprimaient moins de PD-1 que celles des individus �� un stade plus avanc�� de la maladie. Ces niveaux plus ��lev��s de PD-1 sur les cellules T CD8+ en phase chronique sont associ��s �� des niveaux r��duits de prolif��ration in vivo ��� comme mesur�� par l���expression de Ki67 ��� sugg��rant que l���expression de PD-1 est partiellement impliqu��e dans cette perte de fonction des cellules T CD8+. De plus, les cellules na��ves s���accumulent en fr��quence lors de la transition de la phase aigue �� la phase chronique de l���infection. Consid��rant que les cellules na��ves expriment d��j�� des hauts niveaux de PD-1, nous avons ��mis l���hypoth��se que l���activation initiale des cellules T chez les individus chroniquement infect��s est affect��e. En r��sum��, nous proposons un mod��le o�� des hauts niveaux d���expression de PD-1 sont associ��s �� (1) un dysfonctionnement de la r��ponse cellulaire T CD8+ et (2) un d��faut d���activation des cellules na��ves ce qui contribue non seulement �� la progression de la maladie mais aussi ce qui va limiter l���efficacit�� de potentiels vaccins dans l���infection par le VIH-1 en emp��chant toute nouvelle r��ponse d�����tre initi��e. Afin de mieux diss��quer la r��ponse immunitaire mise en place lors d���une infection comme celle du VIH-1, nous avons d��velopp�� un outil qui permet de d��tecter les cellules T CD4+ i.e. des t��tram��res de CMH de classe II. Ces r��actifs ont pour but d���augmenter l���avidit�� du CMH de classe II pour son ligand et donc de d��tecter des TCR de faible affinit��. Dans cette th��se, nous d��crivons une m��thode originale et efficace pour produire diverses mol��cules de HLA-DR liant de fa��on covalente le peptide antig��nique. Mieux d��terminer les m��canismes responsables de l���exhaustion des cellules T dans l���infection par le VIH-1 et de la progression de la maladie, ainsi que d��velopper des outils de pointe pour suivre ces r��ponses T, est central �� une meilleure compr��hension de l���interaction entre le virus et le syst��me immunitaire de l���h��te, et permettra ainsi le d��veloppement de strat��gies pertinentes pour lutter contre l���infection par le VIH-1.
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A L-arginina �� reconhecida como um nutriente de fundamental import��ncia na resposta imune, apesar de seus efeitos serem, por vezes, considerados inconstantes. O autoimplante espl��nico tem sido proposto como alternativa �� esplenectomia total isolada, mas existem preocupa����es quanto �� efic��cia do restabelecimento da resposta imune, haja vista que o paciente pode permanecer com risco aumentado de desenvolvimento de infec����o fulminante p��s esplenectomia, mesmo ap��s a regenera����o morfol��gica do ��rg��o. O objetivo deste estudo foi avaliar a participa����o da suplementa����o diet��tica com L-arginina em subpopula����es linfocit��rias no sangue, no ba��o e nos autoimplantes espl��nicos de ratos submetidos a esplenectomia isolada ou combinada com autoimplante espl��nico. Foram utilizados 42 ratos Sprague-Dawley machos, randomicamente distribu��dos em seis grupos: 1 Controle opera����o simulada; 2 esplenectomia total; 3 esplenectomia total combinada com autoimplante espl��nico; 4 Controle opera����o simulada, com suplementa����o de L-arginina; 5 esplenectomia total, com suplementa����o de L-arginina; e 6 esplenectomia total combinada com autoimplante espl��nico, com suplementa����o de L-arginina. Os animais dos grupos 4, 5 e 6 receberam suplementa����o de L-arginina, uma vez ao dia, durante 15 dias anteriores a coleta sang����nea realizada imediatamente antes dos procedimentos operat��rios (semanas 0 e 12). A dose utilizada foi de 1,0 g/kg/dia, administrada por via intrag��strica em bolus. As avalia����es foram realizadas por meio de hemograma e citometria de fluxo. A an��lise estat��stica utilizou testes param��tricos e n��oparam��tricos, sendo p<0,05 considerado para a rejei����o da hip��tese nula. A suplementa����o com L-arginina acarretou eleva����o da contagem relativa e absoluta de neutr��filos perif��ricos, 12 semanas ap��s a realiza����o de esplenectomia total combinada com autoimplante espl��nico. A esplenectomia total ocasionou diminui����o da contagem relativa de linf��citos T totais, T CD4+ e T CD8β no sangue, mas a suplementa����o diet��tica com L-arginina evitou a diminui����o do percentual de c��lulas T totais e T CD8β no sangue dos animais submetidos a autoimplante espl��nico. Tanto a realiza����o de autoimplante espl��nico como a suplementa����o de L-arginina previnem a diminui����o da subpopula����o de linf��citos T CD4+ no sangue perif��rico, fato que usualmente ocorre ap��s realiza����o de esplenectomia total. Houve maior prolifera����o de c��lulas brancas / g de tecido nos autoimplante espl��nico dos animais suplementados, por��m a suplementa����o n��o influenciou a contagem de linf��citos T, T CD4+ e B de zona marginal de ba��o. A suplementa����o do amino��cido L-arginina ap��s a realiza����o de esplenectomia total combinada com autoimplante espl��nico em ratos foi capaz de reverter altera����es observadas em algumas das subpopula����es linfocit��rias, ocasionadas pela esplenectomia.
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Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)
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Une petite population de lymphocytes T exprimant les deux cor��cepteurs CD4 et CD8 et appel��e double positive (DP), a ��t�� d��tect��e dans le sang p��riph��rique de donneurs sains et de patients atteints de diverses pathologies dont la scl��rose en plaques (SEP). Nous avons ��mis l���hypoth��se qu���il s���agissait de lymphocytes T hautement activ��s pouvant contribuer �� l���inflammation chronique pr��sente dans la SEP. Nous avons compar�� les cellules T DP obtenues du sang de donneurs sains et de patients atteints de la SEP et non trait��s. La fr��quence des cellules DP ��tait similaire chez les patients et les donneurs sains. La proportion de lymphocytes T DP qui exprimaient les chaines du r��cepteur de l���interleukine-15 (IL-15) ��tait plus ��lev��e que pour les autres populations lymphocytaires. Des mesures d���induction de la phosphorylation du STAT5 (signal transducer and activator of transcription) ont d��montr�� que les cellules DP ont r��pondu �� des doses plus faibles et pour de plus longues p��riodes �� l���IL-15 comparativement aux autres lymphocytes T. Le pourcentage de lymphocytes T DP ayant la capacit�� de produire l���interf��ron-gamma et des enzymes lytiques ��tait ��lev�� chez les t��moins sains mais ces niveaux ��taient significativement r��duits chez les patients atteints de la SEP. La caract��risation ph��notypique de cellules DP a sugg��r�� que ces cellules ont des propri��t��s similaires aux lymphocytes T activ��s. Bien qu���il ne s���agisse que d���une caract��risation partielle, il semble que les lymphocytes T DP perdent une partie de leurs propri��t��s chez les patients atteints de la SEP.
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Neisseria meningitidis sorogrupo C (MenC) tem sido causador de surtos no Brasil, desde 2005. Vacinas conjugadas contra MenC est��o dispon��veis desde 1999 nos pa��ses desenvolvidos e mais recentemente no Brasil. S��o vacinas eficazes em pacientes imunologicamente normais, mas pouco se conhece sobre o impacto em pacientes HIV+. O objetivo principal deste estudo foi investigar se h�� alguma correla����o entre a resposta de LT CD4+ de mem��ria e a resposta de anticorpos espec��ficos para o MenC, assim como conhecer as popula����es de mem��ria dos LT CD8+, em crian��as e adolescentes infectados pelo HIV respondedores ou n��o �� vacina MenC conjugada. Amostras de sangue de 36 pacientes HIV+ foram coletadas antes e ap��s imuniza����o, para an��lises laboratoriais, soros e c��lulas coletadas foram congelados e enviados ao nosso laborat��rio para a an��lise da resposta imune humoral e celular. Utilizamos o ensaio bactericida para avaliar a resposta humoral e dividir a popula����o de estudo em soroconversor positivo e soroconversor negativo. A citometria de fluxo foi aplicada para identifica����o das seis subpopula����es de LT CD4+ e T CD8+ e avalia����o do perfil de ativa����o. N��o encontramos mudan��as no perfil de distribui����o das subpopula����es antes e ap��s a vacina����o. A subpopula����o LT CD4+ Int correlacionou positivamente com os t��tulos de anticorpos e a ativa����o, de um modo geral, estava elevada nos respondedores, conferindo certa import��ncia para essa c��lula. Semelhan��as foram observadas entre as subpopula����es LT CD4+ e T CD8+. Em suma, este estudo revelou importantes associa����es entre a resposta de anticorpos bactericidas ap��s a vacina����o, o perfil de distribui����o das subpopula����es de LT CD4+ LT CD8+ e seu status de ativa����o.
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B and T lymphocyte attenuator (BTLA) is a negative regulator of T cell activation, but its function in vivo is not well characterized. Here we show that mice deficient in full-length BTLA or its ligand, herpesvirus entry mediator, had increased number of memory CD8(+) T cells. The memory CD8(+) T cell phenotype resulted from a T cell-intrinsic perturbation of the CD8(+) T cell pool. Naive BTLA-deficient CD8(+) T cells were more efficient than wild-type cells at generating memory in a competitive antigen-specific system. This effect was independent of the initial expansion of the responding antigen-specific T cell population. In addition, BTLA negatively regulated antigen-independent homeostatic expansion of CD4(+) and CD8(+) T cells. These results emphasize two central functions of BTLA in limiting T cell activity in vivo.
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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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Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)
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The pathology of relapsing-remitting multiple sclerosis (RR-MS) is largely attributed to activated autoreactive effector T lymphocytes. The influence of microRNAs on the immune response has been shown to occur in different pathways of lymphocyte differentiation and function. Here, the expression of the miRNAs miR-15a/161 in PBMC, CD4(+), and CD8(+) from RR-MS patients has been investigated. BCL2, a known miR-15a/16-1 target, has also been analyzed. The results have shown that miR-15a/16-1 is downregulated in CD4(+) T cells, whereas BCL2 is highly expressed in RR-MS patients only. Our data suggest that miR-15a/16-1 can also modulate the BCL2 gene expression in CD4(+) T cells from RR-MS patients, thereby affecting apoptosis processes.
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T lymphocytes lacking the lymph node-homing receptors L-selectin and CCR7 do not migrate to lymph nodes in the steady state. Instead, we found here that lymph nodes draining sites of mature dendritic cells or adjuvant inoculation recruited L-selectin-negative CCR7- effector and memory CD8+ T cells. This recruitment required CXCR3 expression on T cells and occurred through high endothelial venules in concert with lumenal expression of the CXCR3 ligand CXCL9. In reactive lymph nodes, recruited T cells established stable interactions with and killed antigen-bearing dendritic cells, limiting the ability of these dendritic cells to activate naive CD4+ and CD8+ T cells. The inducible recruitment of blood-borne effector and memory T cells to lymph nodes may represent a mechanism for terminating primary and limiting secondary immune responses.
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Little is currently known about the lymphocyte populations in the normal and diseased canine gut. The aim of this study was thus the phenotypical and functional characterization of canine intestinal intraepithelial lymphocytes (IEL). IEL were isolated from full-thickness biopsies of 15 adult Swiss Beagle dogs (mean age 8.2 +/-2.8 years) and compared to mesenteric lymph node cells. The phenotypical characterization by multi-parameter flow cytometry revealed that canine IEL differ substantially from lymph node T cells, and consist of various unconventional lymphocyte subsets, unique to mucosal surfaces. These include gammasigma T cells, and CD4(-)CD8(-) and CD8alphaalpha(+) T cells. IEL populations in adult dogs were also compared to those isolated from neonatal Beagle dogs. Analysis revealed a high frequency of undifferentiated CD4(-)CD8(-) T cells in newborn dogs whereas mature CD4(+) and CD8(+) T cells predominate in adult dogs, indicating maturation of the intestinal immune system during development. As IEL in other species are thought to exhibit regulatory functions, we investigated the role of IEL on the activation-induced proliferation of lymph node T cells. While IEL alone did not show activation-induced proliferation, they significantly inhibited the proliferation of activated lymph node T cells in a cell number-dependent manner. These findings are the first to demonstrate that canine intestinal IEL have an immunoregulatory phenotype, which may contribute to the maintenance of intestinal immune homeostasis and may, therefore, be lost in canine chronic enteropathies.
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Although Fas ligand (FasL) is well characterized for its capacity to deliver a death signal through its receptor Fas, recent work demonstrates that FasL also can receive signals facilitating antigen (Ag)-specific proliferation of CD8+ T cells. The fact that the gld mutation differentially influences the proliferative capacity of CD8+ and CD4+ T cells presented the intriguing possibility that a single molecule may play opposing roles in these two subpopulations. The present study focuses on how these positive and negative regulatory roles are balanced. We show that naive CD4+ T cells are responsive to FasL-mediated costimulation on encounter with Ag when Fas-mediated death is prevented. Thus, the machinery responsible for transducing the FasL positive reverse signal operates in both CD4+ and CD8+ T cells. Instead, differential control of FasL expression distinguishes the role of FasL in these two T cell subpopulations. FasL costimulation occurs immediately on T cell receptor ligation and correlates with the up-regulation of FasL expression on CD8+ and naive CD4+ T cells, both of which are sensitive to the FasL costimulatory signal. Conversely, FasL-initiated death occurs late in an immune response when high levels of FasL expression are maintained on CD4+ T cells that are sensitive to Fas-mediated death, but not on CD8+ T cells that are relatively insensitive to this signal. This careful orchestration of FasL expression during times of susceptibility to costimulation and conversely, to death, endows FasL with the capacity to both positively and negatively regulate the peripheral T cell compartment.
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Multiple sclerosis (MS) is a common cause of neurological disability in young adults. The disease generally manifests in early to middle adulthood and causes various neurological deficits. Autoreactive T lymphocytes and their associated antigens have long been presumed important features of MS pathogenesis. The Protein tyrosine phosphatase receptor type C gene (PTPRC) encodes the T-cell receptor CD45. Variations within PTPRC have been previously associated with diseases of autoimmune origin such as type 1 diabetes mellitus and Graves' disease. We set out to investigate two variants within the PTPRC gene, C77G and C772T in subjects with MS and matched healthy controls to determine whether significant differences exist in these markers in an Australian population. We employed high resolution melt analysis (HRM) and restriction length polymorphism (RFLP) techniques to determine genotypic and allelic frequencies. Our study found no significant difference between frequencies for PTPRC C77G by either genotype (��2 = 0.65, P = 0.72) or allele (��2 = 0.48, P = 0.49). Similarly, we did not find evidence to suggest an association between PTPRC C772T by genotype (��2 = 1.06, P = 0.59) or allele (��2 = 0.20, P = 0.66). Linkage disequilibrium (LD) analysis showed strong linkage disequilibrium between the two tested markers (D' = 0.9970, SD = 0.0385). This study reveals no evidence to suggest that these markers are associated with MS in the tested Australian Caucasian population. Although the PTPRC gene has a significant role in regulating CD4+ and CD8+ autoreactive T-cells, interferon-beta responsiveness, and potentially other important processes, our study does not support a role for the two tested variants of this gene in MS susceptibility in the Australian population.
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BACKGROUND: A peptide vaccine was produced containing B and T cell epitopes from the V3 and C4 Envelope domains of 4 subtype B HIV-1 isolates (MN, RF, CanO, & Ev91). The peptide mixture was formulated as an emulsion in incomplete Freund's adjuvant (IFA). METHODS: Low-risk, healthy adult subjects were enrolled in a randomized, placebo-controlled dose-escalation study, and selected using criteria specifying that 50% in each study group would be HLA-B7+. Immunizations were scheduled at 0, 1, and 6 months using a total peptide dose of 1 or 4 mg. Adaptive immune responses in16 vaccine recipients and two placebo recipients after the 2nd immunization were evaluated using neutralization assays of sera, as well as ELISpot and ICS assays of cryopreserved PBMCs to assess CD4 and CD8 T-cell responses. In addition, (51)Cr release assays were performed on fresh PBMCs following 14-day stimulation with individual vaccine peptide antigens. RESULTS: 24 subjects were enrolled; 18 completed 2 injections. The study was prematurely terminated because 4 vaccinees developed prolonged pain and sterile abscess formation at the injection site-2 after dose 1, and 2 after dose 2. Two other subjects experienced severe systemic reactions consisting of headache, chills, nausea, and myalgia. Both reactions occurred after the second 4 mg dose. The immunogenicity assessments showed that 6/8 vaccinees at each dose level had detectable MN-specific neutralizing (NT) activity, and 2/7 HLA-B7+ vaccinees had classical CD8 CTL activity detected. However, using both ELISpot and ICS, 8/16 vaccinees (5/7 HLA-B7+) and 0/2 controls had detectable vaccine-specific CD8 T-cell responses. Subjects with moderate or severe systemic or local reactions tended to have more frequent T cell responses and higher antibody responses than those with mild or no reactions. CONCLUSIONS: The severity of local responses related to the formulation of these four peptides in IFA is clinically unacceptable for continued development. Both HIV-specific antibody and T cell responses were induced and the magnitude of response correlated with the severity of local and systemic reactions. If potent adjuvants are necessary for subunit vaccines to induce broad and durable immune responses, careful, incremental clinical evaluation is warranted to minimize the risk of adverse events. TRIAL REGISTRATION: ClinicalTrials.gov NCT00000886.
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T cell activation leads to engagement of cellular metabolic pathways necessary to support cell proliferation and function. However, our understanding of the signal transduction pathways that regulate metabolism and their impact on T cell function remains limited. The liver kinase B1 (LKB1) is a serine/threonine kinase that links cellular metabolism with cell growth and proliferation. In this study, we demonstrate that LKB1 is a critical regulator of T cell development, viability, activation, and metabolism. T cell-specific ablation of the gene that encodes LKB1 resulted in blocked thymocyte development and a reduction in peripheral T cells. LKB1-deficient T cells exhibited defects in cell proliferation and viability and altered glycolytic and lipid metabolism. Interestingly, loss of LKB1 promoted increased T cell activation and inflammatory cytokine production by both CD4(+) and CD8(+) T cells. Activation of the AMP-activated protein kinase (AMPK) was decreased in LKB1-deficient T cells. AMPK was found to mediate a subset of LKB1 functions in T lymphocytes, as mice lacking the ��1 subunit of AMPK displayed similar defects in T cell activation, metabolism, and inflammatory cytokine production, but normal T cell development and peripheral T cell homeostasis. LKB1- and AMPK��1-deficient T cells each displayed elevated mammalian target of rapamycin complex 1 signaling and IFN-�� production that could be reversed by rapamycin treatment. Our data highlight a central role for LKB1 in T cell activation, viability, and metabolism and suggest that LKB1-AMPK signaling negatively regulates T cell effector function through regulation of mammalian target of rapamycin activity.