Non-specific immunity to Plasmodium falciparum: in vitro studies.

Peripheral blood mononuclear cells (PBM) were cultured with Plasmodium falciparum malaria for several cycles of parasite growth. Non-immune PBM inhibited P. falciparum more frequently than immune PBM. The inhibiting factor appears to be released during the first 24 hours of culture and is a non-dialysable factor, probably originating from monocytes. The relevance of these findings to in vivo immunity is discussed.