Inhibition of lymphocyte transformation by mepacrine and chloroquine

Abstract
Mepacrine inhibited the uptake and the incorporation of leucine, thymidine and uridine into acid-insoluble material in human lymphocytes stimulated by phytohaemagglutinin (PHA) in vitro. The IC50 for each uptake was of the order of 2μM. Mepacrine was inhibitory if applied at any time up to 48 h after PHA. The inhibition differed from that produced by colchicine and prostaglandin E1. The dose-response curve was steep, nearly all incorporation being inhibited by 2 × IC50. Chloroquine also had a steep dose-response curve, was about one-fifth as potent as mepacrine and was maximally effective in the first 6 h after PHA.