AbstractBecause of the national epidemic of cocaine abuse and the increasing prevalence of infectious diseases among drug abusers, we investigated the effects of cocaine and cocaine metabolites on human cellular immune functions. Mononuclear cells (MNC) were isolated from blood of healthy adult volunteers. MNC were stimulated in vitro with mitogens with and without various concentrations of cocaine. Because of cocaine's poor stability in vitro, we found it necessary to replenish cocaine daily to MNC cultures. Under these conditions, cocaine, in a dose response fashion, significantly inhibited MNC proliferation: Metabolites of cocaine did not alter MNC proliferative responses significantly from control cultures. Polymorphonuclear leukocyte chemotaxis was also significantly impaired by cocaine. Our data demonstrate that cocaine is immunosuppressive and that it acts on human MNC during early stages of cellular activation. These data further suggest that illicit cocaine use may compromise the integrity of the immune system.