Immune alterations in morphine-treated rhesus monkeys

The effect of morphine treatment on immunocompetence was investigated in rhesus monkeys (Mucaca mulatta). Monkeys that received morphine daily (3.2 mg/kg) had suppressed peripheral blood mononuclear cell (PBMC) natural killer (NK) activity as well as a decrease in the percentage of CD8⁺CD16⁺ cells compared with saline-treated (controls) or infrequently treated (i.e., opioids once or twice weekly) monkeys. However, an increase (20 ± 5%) in the percentage of CD8⁺ lymphocytes was found in both the daily and infrequent opioid-treated monkeys compared with controls. Conversely, the percentage of total CD4⁺ lymphocytes and CD4⁺CD45RA⁺ was reduced (12 ± 2% and 28 ± 10% respectively) in both daily and infrequent opioid-treated animals compared with saline-treated controls. In a reciprocal fashion, there was an increase in the CD4⁺CD29⁺ population in daily morphine-treated monkeys (54% of the total CD4⁺ cells) compared with untreated animals (37% of the total CD4⁺ cells). In addition, cultured PBMC obtained from monkeys treated daily with morphine produced significantly (P < .01) more polyclonal immunoglobulin (Ig) G (366 ng/ml) and polyclonal IgM (233 ng/ml) compared with PBMC production of polyclonal IgG (96 ng/ml) and polyclonal IgM (67 ng/ml) from saline-treated controls. However, no differences were found in the percentage of CD19⁺ lymphocytes among any of the groups. In summary, daily treatment with a relatively low dose of morphine (3.2 mg/kg) affects immunocompetence which could have important implications in the regulation of viral pathogens in i.v. drug abusers (e.g., AIDS).