Cytokine production in major depression. The role of proinflammatory cytokines and Th1/Th2 dysfunction

Over the years a body of evidence has been accumulated suggesting that major depression is associated with dysfunction of immune reactions. Depressed patients exhibiting dysregulation of HPA-axis and excessive production of glucocorticoids have at the same time enhanced proinflammatory response but suppressed lymphocyte proliferative reactivity and delayed-type hypersensitivity skin response.
The goal of this study was to investigate whether depression is associated with impaired production of several cytokines which, as it is known, are mainly the products of monocytes/macropages such as IL-1β, IL-6, IFN-α, TNF-α and also T lymphocytes subtypes Th1/Th2 such as IL-2, IFN-γ and IL-4, IL-10, respectively.
We studied 29 hospitalized patients who met the criteria for major depressive disorder and 30 healthy control subjects, matched for age and gender. Depressed patients had elevated serum level of proinflammatory cytokine such as IL-1β. Significantly increased IL-1β level in vivo was connected with a decrease of its production after stimulation in vitro with a strong inducer (LPS), however these differences were not statistically significant. Moreover, we also detected a defect in IFN-α in vivo release and in vitro synthesis, which might influence the cytokines production by Th1/Th2 lymphocytes, observed as significant decrease in IL-10 serum concentrations and/or decrease in IL-2 production in blood cell cultures.
The role of the observed overproduction of proinflammatory cytokines and the imbalance in Th1/Th2 cytokines in depression has been discussed.