Altered expression of CD4+CD25+ regulatory T cells and its 5-HT1a receptor in patients with major depression disorder

Background: There is growing interest in immune imbalance observed in major depression, but the mechanism of this imbalance is still not well understood. CD4(+)CD25(+) regulatory T (Treg) cells are known to play an important role in immune regulation. However, their role in major depression has rarely been explored. The aims of this study are to determine the immune imbalance status in patients when first diagnosed with major depression, and to explore possible indications of Treg cell involvement in immune imbalance of major depression. Methods: 27 patients with major depression and 27 healthy individuals were recruited in the study. The immune imbalance was observed by the analysis of Th cell cytokines and CD4(+) CD25(+) Treg cell level. The 5-HT in peripheral serum was measured with HPLC, and changes of Foxp3 and 5-HT1a receptor were observed by RT-PCR and double-immunofluorescence. Results: Despite the similar total lymphocyte count between patients and healthy individuals, the Th1/Th2 ratio increased and the CD4(+)CD25(+) Treg cells decreased in patients' peripheral blood. Moreover, we found that the level of 5-HT was decreased in peripheral serum, and the expression of 5-HT1a receptor was also decreased in peripheral lymphocytes of major depression patients, notably in the CD4(+)CD25(+) Treg cells rather than CD4(+)CD25(-) T cells. Limitations: The details of interaction between 5-HT1a receptors and Treg cells in major depression need further exploration. Conclusion: CD4(+)CD25(+) Treg cells may contribute to the immune imbalance in patients with major depression, which could involve its interaction with 5-HT system. (C) 2009 Elsevier B.V. All rights reserved.