Plasmodium falciparum varies in its ability to induce tumor necrosis factor

Tumor necrosis factor (TNF) has a variety of protective and pathological actions in human malaria. We report that different laboratory lines of Plasmodium falciparum which were derived from a single wild isolate (IT 4/25/5) varied widely in their ability to stimulate TNF production by human mononuclear cells. In the cloned line R29 we observed that subcultures selected for high rosetting frequency gave significantly higher levels of TNF stimulation than subcultures with low rosetting frequency, indicating that TNF induction can vary within populations that have originated from a single genotype. These results raise the possibility that the clinical severity of malaria is partly determined by the TNF-inducing activity of the infecting strain of parasite.