Drugs of Abuse and the Immune System

It has been clearly demonstrated that opioids, cannabinoids, and cocaine alter a variety of assays of immune function when added to cells of the immune system in vitro. Receptors and/or mRNA for the receptors for opioids and cannabinoids have been demonstrated in a variety of cells of the immune system. In many cases, especially for the opioids, pharmacological specificity of the action of the drugs has been verified using appropriate antagonists. These observations provide a biological basis for concluding that drugs of abuse have direct affects on immune cells. In addition, all three drugs alter immune responses of rodents, and in some cases, humans, when treated in vivo. In vivo mechanisms of action may be harder to determine as the drugs may activate other physiologic systems in the body that may also impinge on immune responsiveness, such as the HPA and the SNS. Nonetheless, drug abusers suffer the cumulative effects of direct and indirect effects of the drugs on the immune system. Assays of immune function that have been measured include effects on the innate immune system, which encompass effects on macrophages and NK cells, and effects on adaptive immunity, which include the humoral and cellular arms of the immune system. Considerable attention has been focused on cytokine and chemokine mediators of immune function that are modulated by the drugs and on their capacity to modulate activation of the various arms of the immune system by polarization of the cytokine profile. Other commonly used and abused drugs include nicotine and alcohol, both of which have marked effects on the immune system, and are frequently part of the panoply of artificial substances used by addicts. In addition, methamphetamines can alter immune status. Due to space limitations the reader is referred to key papers on these subjects (Sopori, 2002; Gamble et al., 2006; Pacifici et al., 2002)