الفهرس 
t lymphocytesOnly 14 pages are availabe for public view
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Abstract
T lymphocytes are the most diverse and versatile of the immune system players. They are the initiators of the immune responses against most pathogens. All parasitic infections induce some kind of immune response, which in some cases is protective and in others causes pathological changes. The aim of this work was to study the T lymphocyte activities and the expression of the costimulatory molecules in some parasitic diseases, especially in schistosomiasis, and to detect their relation to the clinical stage of the disease and the intensity of infection. This case-control study was carried out on 96 patients with different parasitic infestations and 12 voluntary healthy control. They were subjected to flow cytometric analysis of peripheral blood mononuclear cells using monoclonal antibodies (MAb) against CD3, CD4, CD8, CD28, and HLA-DR. In patients with chronic schistosomiasis, there was a significant decrease in CD3+, CD4+, CD8+ T lymphocytes and the expression of the costimulatory molecule CD28 on CD8+ T lymphocytes, while the activation marker HLA-DR expression on CD4+ T lymphocytes was increased. These changes were more obvious with the progression of the clinical stages and the increase in intensity of infection. Increased T cell activation and decreased expression of the costimulatory molecule CD28 on CD8+ T lymphocytes were also detected in patients with intestinal ascariasis, filarial elephantiasis, and toxoplasmosis. From the results of this study, it could be concluded that chronic parasitic infections cause chronic immune stimulation in tropical areas and developing world that may predispose to a higher prevalence of HIV infection. chronic immune activation by chronic schistosomiasis is closely related to the clinical stage of the disease and the intensity of infection.