Natural killer cell activity in depressive illness: preliminary report.

The central nervous system and the immune system are closely interrelated. Stress and psychiatric illness have previously been associated with immune dysregulation (Calabrese et al. 1987). We reported earlier that patients with major depression manifested a reduction in mitogeninduced lymphocyte proliferation, a correlate of cellular immune function (Kronfol et al. 1983). These findings were later confirmed by other investigators (Schleifer et al. 1984). We now report our preliminary results on Natural-Killer (NK) cell activity, a more specific parameter of immune function directed against tumoror virus-infected cells, in 12 drug-free patients diagnosed with major depressive disorder and 12 ageand sex-matched normal controls.