Cytokine control of parasite-specific anergy in human urinary schistosomiasis. IL-10 modulates lymphocyte reactivity.

Humans chronically infected with schistosomiasis usually have impaired parasite Ag-specific lymphocyte proliferation and IFN-gamma production that may facilitate persistence of the parasite while producing little clinical disease. The mechanisms that contribute to the immunologic hyporesponsiveness in these patients remain undefined. IL-10 has been shown to exert an inhibitory effect on cell-mediated immunity.

CD28 activation promotes Th2 subset differentiation by human CD4+ cells.

Ligation of CD28 provides a costimulatory signal to T cells necessary for their activation resulting in increased interleukin (IL)-2 production in vitro, but its role in IL-4 and other cytokine production and functional differentiation of T helper (Th) cells remains uncertain. We studied the pattern of cytokine production by highly purified human adult and neonatal CD4+ T cells activated with anti-CD3, phorbol 12-myristate 13-acetate (PMA) and ionomycin, or phytohemagglutinin (PHA) in the presence or absence of anti-CD28 in repetitive stimulation-rest cycles. Initial stimulation of CD4+ cells with anti-CD3 (or the mitogens PHA or PMA+ionomycin) and anti-CD28 monoclonal antibodies induced IL-4, IL-5 and interferon-gamma (IFN-gamma) production and augmented IL-2 production (6- to 11-fold) compared to cells stimulated with anti-CD3 or mitogen alone.