Mechanism of protection induced by vitamin A in falciparum malaria.

Supplementation with vitamin A potentiates host resistance to malaria, however, the underlying mechanism is unknown. We tested the effects of 9-cis-retinoic acid, a metabolite of vitamin A, on CD36 expression, non-opsonic phagocytic clearance of parasitised erythrocytes, and TNFalpha production in human monocytes and macrophages. We found reduced secretion of TNFalpha, upregulated CD36 expression, and increased phagocytosis of Plasmodium falciparum-parasitised erythrocytes. Increased parasite clearance and reduced proinflammatory cytokine responses to infection might partly explain the beneficial effects of supplementation with vitamin A in malaria.