Growth inhibition of Plasmodium falciparum and interleukin-8 production by peripheral blood mononuclear and polymorphonuclear cells in vitro.

Peripheral blood mononuclear and polymorphonuclear cells have been demonstrated to kill and inhibit malaria parasite proliferation in vitro, but most of the reports required activation of the cells by cytokines or presence of immune sera or opsonins. In our study, peripheral blood leukocytes from non-immune donor efficiently inhibited Plasmodium falciparum growth, depending on the effecter/target ratio. Moreover, these cells produced a large amount of interlenkin-8 (IL-8) under stimulation with infected erythrocytes or supernatant of the Plasmodium falciparum culture. IL-8 secretion in the culture supernatant of polymorphonuclear cells was noted from 6-9 hr of stimulation with the parasites, with a substantial increase over 24 hours of culture. Attempt to elucidate whether IL-8 was involved in malaria suppression was done, and the result suggested that IL-8 was not directly involved in the anti-malarial activity of the mononuclear and polymorphonuclear cells. The other mechanism besides IL-8 may work for inhibiting parasite growth in the culture system of malaria parasites associated with leukocytes.