The Relevance of Opioids and Opioid Receptors on Immunocompetence and Immune Homeostasis 1

Summary

Our understanding of the impact of opioid compounds on the function of the immune system has expanded greatly over the past 5 years. It is now clear that several cell populations serve as targets for the effects of the opioids, and this includes T cells, macrophages, and NK cells. The mechanism(s) of immunomodulation are now being described in greater detail on both a cellular and biochemical level. Indeed, the finding that the production of lymphokines and cytokines may be altered following opioid treatment may be particularly important since all immune responses are dependent to some degree on the synthesis of these protein mediators.

The opioid receptors have now been successfully cloned from cells of the immune system. There is no longer serious doubt about the presence of opioid receptors expressed by these cell populations. Extremely valuable information regarding the role of the opioid receptors in the function of the cells of the immune system should be obtained using molecular methods. Clearly, the molecular basis for the effect of the opioid compounds on the immune response represents a critical area of research in the immediate years ahead.

It is not surprising that opioid compounds have been found to alter resistance to infectious agents, since a great deal of evidence shows that these compounds modulate the immune response. The significance of the drugs of abuse in the host-parasite interaction for a number of microorganisms, including HIV, remains a critical area for additional research. In addition, because of the importance of opportunistic infections in the AIDS patients, the impact of opioids on the resistance to these infectious agents is also a matter of great concern. It is possible that combinations of certain drugs of abuse may serve to alter resistance to some, but not all, of these infectious diseases. In any case, answers to these questions will most certainly come only once a greater understanding of the basic mechanisms of immunomodulation is achieved.