IL-6 induced by IL-1 inhibits malaria pre-erythrocytic stages but its secretion is down-regulated by the parasite.

The capacity of IL-6 to mediate the antiparasitic activity of IL-1 on intrahepatic development of malaria parasite was demonstrated. The comparisons of IL-6 levels in infected and noninfected hepatocyte cultures, either purified or enriched with nonparenchymal cells and stimulated by IL-1 or IL-6, indicate that subtle interactions exist between intrahepatocytic development of Plasmodium yoelii and liver synthesis of IL-6. During its intrahepatic multiplication, the parasite causes a decline in IL-6 production. IL-6 mRNA was not detected in the livers of infected mice during development of either hepatic or blood stage parasites although IL-6 activity was found in the sera during both stages.