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CTLA-4 Expression (ctla-4 + expression)
Selected AbstractsHIV-1 impairs in vitro priming of naïve T cells and gives rise to contact-dependent suppressor T cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2010Karlhans F. Che Abstract Priming of T cells in lymphoid tissues of HIV-infected individuals occurs in the presence of HIV-1. DC in this milieu activate T cells and disseminate HIV-1 to newly activated T cells, the outcome of which may have serious implications in the development of optimal antiviral responses. We investigated the effects of HIV-1 on DC,naïve T-cell interactions using an allogeneic in vitro system. Our data demonstrate a dramatic decrease in the primary expansion of naïve T cells when cultured with HIV-1-exposed DC. CD4+ and CD8+ T cells showed enhanced expression of PD-1 and TRAIL, whereas CTLA-4 expression was observed on CD4+ T cells. It is worth noting that T cells primed in the presence of HIV-1 suppressed priming of other naïve T cells in a contact-dependent manner. We identified PD-1, CTLA-4, and TRAIL pathways as responsible for this suppresion, as blocking these negative molecules restored T-cell proliferation to a higher degree. In conclusion, the presence of HIV-1 during DC priming produced cells with inhibitory effects on T-cell activation and proliferation, i.e. suppressor T cells, a mechanism that could contribute to the enhancement of HIV-1 pathogenesis. [source] Abnormal CTLA-4 function in T cells from patients with systemic lupus erythematosusEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 2 2010Elizabeth C. Jury Abstract CTLA-4 is a critical gatekeeper of T-cell activation and immunological tolerance and has been implicated in patients with a variety of autoimmune diseases through genetic association. Since T cells from patients with the autoimmune disease systemic lupus erythematosus (SLE) display a characteristic hyperactive phenotype, we investigated the function of CTLA-4 in SLE. Our results reveal increased CTLA-4 expression in FOXP3, responder T cells from patients with SLE compared with other autoimmune rheumatic diseases and healthy controls. However, CTLA-4 was unable to regulate T-cell proliferation, lipid microdomain formation and phosphorylation of TCR-, following CD3/CD28 co-stimulation, in contrast to healthy T cells. Although lupus T cells responded in vitro to CD3/CD28 co-stimulation, there was no parallel increase in CTLA-4 expression, which would normally provide a break on T-cell proliferation. These defects were associated with exclusion of CTLA-4 from lipid microdomains providing an anatomical basis for its loss of function. Collectively our data identify CTLA-4 dysfunction as a potential cause for abnormal T-cell activation in patients with SLE, which could be targeted for therapy. [source] Suppressive properties of human CD4+CD25+ regulatory T,cells are dependent on CTLA-4 expressionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2004Brigitte Birebent Abstract It has been demonstrated that T,cells with regulatory properties are present within the peripheral blood CD4+CD25+ T,cell compartment. Here, we describe an original method to purify human CD4+CD25+CD152+ T,lymphocytes as living cells by forcing the exportation of CTLA-4 molecules stored in intracellular vesicules at the cell surface. By doing so, we demonstrate that CD4+CD25+ T,cells contain a smaller and more homogeneous population enriched in cells with in vitro regulatory activity. Moreover, we show that this enrichment in regulatory T,cells is associated with an increased expression of Foxp3 and that CD4+CD25+CD152+ T,lymphocytes display a much stronger suppressive activity in controlling in vitro proliferation of alloantigen-specific T,cells than CD4+CD25+CD152, T,lymphocytes purified in parallel. Lastly, by purifying such cells expressing CTLA-4, we demonstrate that indeed CTLA-4 is involved in CD4+CD25+CD152+ T,cell regulatory activity, while suppressive cytokines are not. [source] CTLA-4 gene promoter and exon 1 polymorphisms in Iranian patients with gastric and colorectal cancersJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 12 2007Abolghasem Hadinia Abstract Background and Aim:, Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a potent immunoregulatory molecule that suppresses antitumor response by down-regulating T-cell activation. Effects of several polymorphisms in CTLA-4 on CTLA-4 expression and function have been previously documented. The aim of this study was to investigate the putative effect of CTLA-4 polymorphisms on susceptibility to gastric and colorectal cancers in an Iranian population. Methods:, A total of 155 patients (109 with colorectal cancer and 46 with gastric cancer) and 190 age- and sex-matched healthy controls were evaluated. Genotyping of ,1722T/C, ,1661A/G, and +49A/G were performed by PCR restriction fragment length polymorphism methods and of ,318C/T by a PCR amplification refractory mutation system technique. Results:, No statistically significant differences were found in the genotype distribution and allele frequencies among patients and controls. Haplotype analysis demonstrated that the TACG haplotype (,1722T, ,1661A, ,318C, +49G) frequency was significant increased in patients with colorectal cancer (P = 0.009) and gastric cancer (P = 0.006) in comparison to the control group. In contrast, the TACA haplotype frequency was significantly decreased in patients with colorectal cancer (P = 0.02) and not significantly decreased in patients with gastric cancer (P = 0.13) compared to the control group. Conclusion:, A positive association between CTLA-4 TACG haplotype and gastric and colorectal cancers was found in an Iranian population. A protective role for TACA haplotype is postulated. [source] CTLA-4 expression in T cells of patients with atopic dermatitisPEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 5 2005Sung Yon Choi Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4; CD152) is a surface molecule of activated T cells with sequence homologous to CD28, and may act as a negative regulator of T-cell activation. In murine animal models, cross-linkage of CTLA-4 molecules on the cell surface results in decreased T-cell proliferation, accompanied by increased interleukin (IL)-2 production and apotosis. To clarify the activation of peripheral blood T cells, we studied the CTLA-4 expression in 32 patients with atopic dermatitis who visited our institution, and 19 normal children who visited for pre-operative laboratory examination were used as normal controls. Whole blood was obtained from all subjects and stained with anti-CD3, anti-CD4, anti-CD8 monoclonal antibodies (mAb). After erythrocyte lysis with lysing solution, the cells were stained with anti-CTLA-4 mAb, and stained cells were analysed by fluorescence-activated cell sorter (FACScan) flow cytometer. Intracellular expression of CTLA-4 was significantly upregulated in peripheral blood CD3+ T cells (36.8%), CD4+ T cells (21.7%) and CD8+ T cells (18.7%) of patients with atopic dermatitis, compared with normal control (18.3%, 9.7%, 9.8%; respectively). Furthermore, CTLA-4-positive CD3+ T cells in patients with severe atopic dermatitis were significantly higher compared with milder group (42.8% vs. 32.2%). However, no significant difference was obtained in CD4+ and CD8+ T cells. Mean percentage of T cells expressing CTLA-4 in patients with atopic dermatitis was higher than the control group. These observations suggest the possibility that the disease activity can be correlated with the CTLA-4 level. [source] Everolimus and Basiliximab Permit Suppression by Human CD4+CD25+ Cells in vitroAMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2005David S. Game Immunosuppressive drugs are essential for the prevention of acute transplant rejection but some may not promote long-term tolerance. Tolerance is dependent on the presence and regulatory function of CD4+CD25+ T cells in a number of animal models. The direct effects of immunosuppressive drugs on CD4+CD25+ cells, particularly those that interfere with IL-2 signaling are uncertain. We studied the effects of the rapamycin derivative everolimus and the anti-CD25 monoclonal antibody basiliximab on the regulatory capacity of human CD4+CD25+ cells in vitro. Both drugs permitted the suppression of proliferation and IFN-, secretion by CD4+CD25, cells responding to allogeneic and other polyclonal stimuli; CTLA-4 expression was abolished on CD4+CD25+ cells without compromising their suppressive ability. Everolimus reduced IFN-, secretion by CD4+CD25, cells before the anti-proliferative effect: this is a novel finding. Exogenous IL-2 and IL-15 could prevent the suppression of proliferation by CD4+CD25+ cells and the drugs could not restore suppression. By contrast, suppression of IFN-, secretion was only slightly impeded with the exogenous cytokines. Finally, CD4+CD25+ cells were more resistant than CD4+CD25, cells to the pro-apoptotic action of the drugs. Together these data suggest that CD4+CD25+ cells may still exert their effects in transplant patients taking immunosuppression that interferes with IL-2 signaling. [source] | ||||||||||