Pre-erythrocytic stages of plasmodia. Role of specific and nonspecific factors.

Protection against pre-erythrocytic stages of malaria is possible as demonstrated by the generation of resistance after immunization with irradiated sporozoites. However, mechanisms involved are more numerous and intricate than previously believed and it progressively appears that the role of the presumed target, the sporozoite, might be negligible compared with that of the hepatic stage. The comparative use of in vivo and in vitro models clearly demonstrates that the intrahepatocytic parasite can be the target of antibodies, cytokines, phagocytic and cytotoxic cells, nonspecific factors--mechanisms in part induced by the previous or subsequent developmental stages.