Parasite-derived mitogenic activity for human T cells in Plasmodium falciparum continuous cultures

Supernatants from Plasmodium falciparum continuous cultures exhibited mitogenic activity against human blood lymphocytes from unsensitized donors. This effect, which was not observed with supernatants from control cultures grown in the absence of the parasites, was dependent upon (i) the concentration of supernatant added to the lymphocyte cultures and (ii) the parasite concentration in the P. falciparum continuous cultures. T cells were the predominant target cells of this mitogenic activity. We observed similar response in lymphocytes from malaria-sensitized individuals to P. falciparum continuous culture material. We also detected a mitogenic activity in parasite-infected erythrocytes from P. falciparum continuous cultures. P. falciparum continuous cultures may provide practical quantities of parasite-derived substances which, presumably, are able to manipulate the immune effector mechanisms of an infected host.