Changing patterns of the IL-2/IL-2R pathway of lymphocyte activation following exposure to Plasmodium falciparum products: a study with squirrel monkey peripheral blood mononuclear cells.

Squirrel monkeys are experimental hosts useful for studies on human malaria. In the present work, in vitro lymphocyte reactivity was measured by proliferation in the presence of Plasmodium falciparum-derived products, and found to depend on the previous malarial status of the animals and upon the source and/or the nature of the P. falciparum-derived material. Special attention was given to the IL-2/IL-2R pathway of lymphocyte activation. Culture supernatant from P. falciparum-parasitized erythrocytes exerted an inhibitory effect towards T lymphocytes obtained from P. falciparum-non-immune squirrel monkeys, when activated, for instance, by PHA. These lymphocytes did not incorporate tritiated thymidine (neither they did proliferate) although they expressed IL-2 alpha and beta binding chains and secreted IL-2 (or at least TCGF). This inhibitory effect could not be rescued by the addition of rhIL-2, although the assayed lymphocytes could retain the ability to continue their cell cycle progression and divide after removal of the P. falciparum-derived inhibitory product(s). The incidence of anti-mitogenic molecules which impair the IL-2/IL-2R pathway of lymphocyte activation in malaria related processes is discussed.