CD8+ T cells inhibit Plasmodium falciparum-induced lymphoproliferation and gamma interferon production in cell preparations from some malaria-immune individuals.

Infection with Plasmodium falciparum induces marked disturbances in normal immunoregulatory functions. Antigen-specific immunosuppression is a feature of acute malaria and has been linked to activation of CD8+ T suppressor cells. Among immune adults, cell-mediated immune responses to malaria antigens are extremely variable when measured in vitro, and there is no obvious relation between responsiveness and resistance to clinical disease. In this study, when CD8+ cells were removed from peripheral blood mononuclear cell preparations obtained from individuals who responded poorly to a soluble malaria antigen preparation, both lymphoproliferation and gamma interferon production were significantly enhanced, but responses to other soluble antigens and mitogen were unaffected. No effect of CD8+ cell depletion was seen in individuals whose undepleted mononuclear cells gave a high response to the malaria antigen. This suggests that for some malaria-exposed individuals, CD8+ cells activated in vitro by exposure to malaria antigens suppress other cellular responses and may obscure the presence of potentially protective immune mechanisms.