Immune function in heroin addicts and former heroin addicts in treatment: pre- and post-AIDS epidemic.

These studies suggest that specific opiate receptors are not involved significantly in modulating NK-cell activity by any direct effect. The role normally played by the endogenous opioids in directly modulating NK-cell cytotoxic activity may be minimal and certainly is not a clinically relevant controlling factor. These findings also suggest that the repeatedly observed lowering of NK-cell activity in untreated heroin addicts is not due to a direct drug effect. It may be due, however, to an indirect drug effect, possibly by way of altering neuroendocrine function, which we and others have shown predictably occurs during cycles of heroin addiction, and which, as discussed above, has been shown to become normalized during steady-dose, long-term, methadone-maintenance treatment. The lowering of NK-cell activity in heroin addicts may also be due primarily to the use of unsterile needles, with exposure to and infection with multiple diseases as well as injection of many foreign substances. Clinical studies of all the important immunological indices will have to be carried out in well-characterized human populations, including normal healthy control subjects, drug abusers, drug addicts, and former drug addicts in defined treatment status, before the actual roles of drugs of abuse or drugs used to treat drug abuse in immune function in humans will be fully understood.