Selective Inhibitory Effects of Stress Hormones on Natural Killer (NK) Cell Activity of Lymphocytes from AIDS Patients

To examine the potential role of stress hormones in the progression of HIV infections, we developed an in vitro model system that investigates the effects of cortisol, adreno-corticotropin-releasing hormone (ACTH) and β-endorphin on the natural killer cell activity of lymphocytes from normal subjects and AIDS patients. The system employs a 4 hr⁵¹Cr release assay and K562 target cells. Direct addition of cortisol (0.05, 0.1, and 0.2 μg/ml) or ACTH (10^-6 to 10^-8 M) to the mixture of effector and prelabeled target cells did not produce any significant immunoregulatory effects on the NK cell activity of normal lymphocytes. Direct addition of β-endorphin (10^-13 to 10^-17 M) to the mixture of effector and prelabeled target cells did not produce any significant immunoregulatory effects on the NK cell activity of lymphocytes from normal or AIDS subjects. However, cortisol and ACTH significantly inhibited the NK activity of lymphocytes from AIDS patients. The selective inhibitory effects of cortisol and ACTH in patients with HIV infections are consistent with a model which proposes that stress related neurohormones and/or neuropeptides may be involved in the progression of HIV infections.