Inconsistent results have been reported concerning circulating lymphocyte subsets in depression. To establish whether the immune alterations in depression could be related to neurovegetative symptoms, lymphocyte subsets were assessed in major depressive and dysthymic patients who exhibited either typical or atypical features (ie, the latter characterized by mood reactivity and reversed neurovegetative features).
Blood was collected from major depressive, atypical depressive, typical dysthymic, or atypical dysthymic patients and from nondepressed control subjects. Circulating lymphocyte subsets (CD3, CD4, CD8, CD19, CD16/CD56) were determined by flow cytometry. In a subset of patients, lymphocyte subsets were also determined after a 12-week course of antidepressant medication.
Although T and B cell populations did not differ between the depressive subtypes and control subjects, circulating natural killer (NK) cells were elevated in depressive illness, and varied as a function of depressive subtype and sex. Among male patients, NK cells were elevated to a greater extent in typical than in atypical depression, and more so in major depressive than in dysthymic patients. Among female patients, circulating NK cells were lower than in male patients, and only among the typical major depressive patients did NK cells exceed those of controls. Normalization of NK cells occurred with successful pharmacotherapy.
Depression may be associated with elevated levels of circulating NK cells. Although the neurovegetative features associated with depression, particularly altered eating, may have contributed to the elevated NK cells, depressive affect itself also contributed in this respect. However, the relative contributions of these factors varied between male and female patients.