Investigations of the cellular immunity during depression and the free interval: evidence for an immune activation in affective psychosis.

1. Results of investigations of the immune function in affective disorders are conflicting. Some authors described an immune suppression, others an immune activation in major depression. The authors performed a study of cellular immunity in the MDD subtype endogenous depression. 23 patients suffering from endogenous depression were investigated during the depressive state, the results were compared with a group of 14 patients during the free interval and 51 healthy controls. 2. The lymphocyte proliferation after incubation with diphtheria- and tetanus toxoid, mainly stimulating T-cells, was reduced but after incubation with an antigen-cocktail, stimulating both, T- and B-cells, was increased in patients during depression and during the free interval compared to controls. 3. The CD3(+)- and CD4(+)-cells were significantly enhanced in both groups of patients while the CD8(+)-cells showed no differences to the controls. The ratio CD4+/CD8+ was increased in patients, too, as described in some autoimmune disorders. 4. The suppressor cell activity was significantly reduced in the PWM-assay and in the PHA-assay. The mixed lymphocyte culture showed a tendency to reduced suppressor cell activity as well. 5. The results point to an immune activation and to a disturbed control of the proliferative activity in affective psychosis. A T-cell related defect, not compensated by an increased number of CD3+- and CD4+ -cells is discussed. 6. From our point of view, the conflicting results of psychoneuroimmunological investigations in depressive disorders may be related to etiologically different subgroups of depression. The diagnostic category of MDD is possibly one of the traps in psychoneuroimmunology.