Effect of histamine on the mitogenic response of human lymphocytes and its modification by cimetidine and levamisole

The phytohaemagglutinin (PHA) mitogenic response of human blood lymphocytes demonstrated a dose-dependent inhibition by histamine (in the range 5 X 10(-7) M). Using suboptimal mitogenic doses of PHA the suppression was more pronounced. Stimulation using different doses of pokeweed mitogen (PWM) was not altered by histamine. Purified T cells and a lymphocyte population depleted of histamine-receptor-bearing cells were less sensitive to the histamine effect. In the supernatants of histamine-stimulated cultures, suppressor factor activity was found. Cimetidine could reverse the effect of histamine in a dose-dependent manner. Adding levamisole to the PHA cultures also produced some antihistaminic effect.