Natural killer cell activity and lymphocyte subsets in parenteral heroin abusers and long-term methadone maintenance patients.

We studied natural killer (NK) activity and lymphocyte subsets in 11 active parenteral heroin abusers, 11 long-term methadone-maintained former heroin abusers and 11 apparently healthy individuals. All subjects were males aged 23 to 49 and none had active infectious or inflammatory diseases. All current or former heroin abusers were seronegative for antibody to human immunodeficiency virus. The methadone maintenance patients were socially rehabilitated and had not abused drugs parenterally for at least 10 years. NK activity was determined by a standard Cr-release cytotoxicity assay using K562 cells as targets, and lymphocyte subsets were determined by direct immunofluorescence using flow cytometry. At all three effector-target ratios (100:1, 50:1 and 25:1), NK activity was reduced significantly (P less than .01) in parenteral heroin abusers compared with methadone maintenance patients and apparently healthy individuals. The latter two groups did not differ from each other. Parenteral heroin abusers also had higher absolute numbers of CD2, CD3, CD4 and CD8-positive cells. These data support our hypothesis that significant abnormalities of cellular immunity in parenteral heroin abusers can be normalized by successful long-term methadone treatment.