Increased serum soluble CD8 or suppressor/cytotoxic antigen concentrations in depression: suppressive effects of glucocorticoids.

There is now some evidence that depression and, in particular, major depression, is accompanied by signs of an immune response, and that there are reciprocal relationships between immune function and increased hypothalamic-pituitary-adrenal (HPA) axis activity in depression. To further examine the above phenomena, this study has assayed serum soluble CD8 (sCD8) concentrations in 22 normal controls, 27 minor depressed, 37 major depressed, and 26 melancholic depressed patients. Serum sCD8 was significantly higher in depressed patients versus normal controls. Thirty-five percent of the depressed subjects had increased sCD8 serum levels (i.e., > 560 U/mL) with a specificity of 95.4%. Dexamethasone administration (1 mg PO) had a significant suppressive effect on serum sCD8. In depressed subjects, there were significant and negative relationships between serum sCD8 and postdexamethasone cortisol values. The results suggest the presence of an ongoing lymphocyte activation in depression, which may be down-regulated by increased HPA axis activity in that illness.