Muramyl dipeptide enhances in vitro peritoneal macrophage phagocytic activity

There is little agreement as to the precise mechanism of action of muramyl dipeptide (MDP) despite a steadily unfolding series of experiments designed for clarification. This report further defines the role of MDP in nonspecific enhancement of host defenses by examining its effect on in vitro macrophage phagocytosis. Peritoneal macrophages were incubated in vitro with muramyl dipeptide. Phagocytic indices were determined using the iodination technique. The macrophages treated with MDP had a significant increase in their phagocytic function compared to control cells, adding to the understanding of the mechanism of action of MDP and raising the possibility of a trial peritonitis in humans.