Abstract
Marijuana and its major psychoactive component, delta-9-tetrahydrocannabinol (THC), alter resistance to bacterial, protozoan, and viral infections in vivo and in vitro. These alterations have been accompanied by modifications in functional components of the immune system. In addition, marijuana and THC, as well as other cannabinoids, have been reported to directly affect functional activities of lymphocytes, macrophages, natural killer cells, and other immunocytes. These include effects on cytokine production resulting in a shift in the balance of Th1 versus Th2 cytokines. Both receptor and non-receptor mediated modes of action have been proposed as causative of cannabinoid effects. Reports that marijuana and THC alter anti-microbial activity in vivo and in vitro indicate that its use presents a potential risk of decreased resistance to infections. However, few controlled longitudinal epidemiologi-cal and immunological studies have been undertaken to correlate the immunosuppressive effects of marijuana smoke or cannabinoids on the incidence of infections or disease in humans.
