Phagocytic function of monocytes of rhesus monkeys during Plasmodium knowlesi infection and the effect of treatment with chloroquine.

The effect of chloroquine on the phagocytic function of monocytes was studied in normal and Plasmodium knowlesi-infected rhesus monkeys during a course of therapy. In normal animals, chloroquine inhibited phagocytic activity after three doses. The effect of the drug and concentration was greatest after six to eight days. Recovery in function of monocytes was noticed after the drug had been excreted. In P. knowlesi-infected monkeys, the degree of inhibition of phagocytosis depends on the level of parasitaemia. Chloroquine treatment reversed the trend of inhibition in the animals that received the drug when parasitaemia was less than 30%.