Enhanced inhibition of in vitro multiplication of Plasmodium falciparum by stimulated human polymorphonuclear leucocytes.

The effect of normal human peripheral blood polymorphonuclear leucocytes on in vitro multiplication of Plasmodium falciparum malaria parasites was investigated. It was shown that normal neutrophils were able to phagocytose parasitized erythrocytes and free parasites and thus inhibit in vitro multiplication of the parasite. Stimulation of the neutrophils by phorbol myristate acetate, a potent stimulus of leucocyte oxidative metabolism, resulted in enhanced inhibition of parasite growth. Superoxide dismutase, scavenger of superoxide anion, catalase, inhibitor of hydrogen peroxide, and sodium azide, inhibitor of myeloperoxidase, did not abrogate the inhibitory ability of the neutrophils. The results indicate that polymorphonuclear leucocytes play an important role in the defence against P. falciparum malaria.