Depression and immunity: clinical factors and therapeutic course

While many reports describe associations between depressive disorders and a ltered immunity, findings have not been fully consistent. Diagnostic subtyp e, demographic factors such as age and gender, medical characteristics, and the immune measures selected for assessment may have contributed to the he terogeneous findings. In a study of 21 medically healthy young adults with major depression, we found, consistent with previous reports, evidence of i ncreased lymphocyte activation to mitogen challenge and decreased natural k iller (NK) cell numbers and function during acute depression. Fifteen subje cts were followed longitudinally. T, CD4(+), CD29(+), and CD45RA(+) lymphoc ytes and T-cell mitogen responses decreased significantly (P < 0.05) during 6 weeks of pharmacotherapy and concurrent clinical improvement. There was no change in NK activity or CD56(+) cells. The longitudinal effects appeare d unrelated to tricyclic antidepressant levels. Changes in the immune syste m with short-term clinical improvement in depressed patients are not unifor m providing further evidence that several mechanisms are involved in the al tered immunity associated with clinical depression. (C) 1999 Elsevier Scien ce Ireland Ltd. All rights reserved.