A Study Of Cytokine And T Cell Immunity Function In Patients With Major Depressive Disorder

Objective:To investigate the pertinence between major depressive disorder and T lymphocyte immunity function,we tested T lymphocyte subsets populations in the peripheral blood and the plasma levels of the relevant cytokines(IL-2,IL-4,IL-6,IL-10,IFN-y and TNF-a),the expression of the immune checkpoint inhibitors of T-cell immunoglobulin and mucin-domain containing-3(TIM-3),programmed cell death protein 1(PD-1)and its two ligands,PD-L1 and PD-L2 on T lymphocytes and monocytes in the patients with major depressive disorder.Methods:Peripheral blood samples were obtained from 22 patients with major depressive disorder(MDD)and 20 healthy controls(HCs).Flow Cytometry was used to test the expression of TIM-3,PD-1,PD-L1,PD-L2 on T lymphocytes and monocytes and the total blood proportion of T lymphocyte subsets.We also analyzed the relevance of immunological index with clinical variables(age of onset,total course of disease,incidence of disease,and scores of HAMD-17,MADRS and YMRS).In addition,Cytometric Bead Array(CBA)was used to test the plasma levels of cytokines(IL-2,IL-4,IL-6,IL-10,IFN-?,and TNF-a)selectively.Results:Compared with the healthy controls,the plasma level of interleukin-6 was obviously increased in patients with MDD(8.94±19.93 vs.0.44±0.68,P=0.032),and the levels of IL-2,IL-4,IL-10,IFN-?,and TNF-? were lower detection limit in most participants,there was no significant difference between with MDD and HCs.About the expression of TIM-3,PD-1,PD-L1,PD-L2 on T lymphocytes and monocytes and the total blood proportion of T lymphocyte subsets(CD3 +,CD4 +,CD8 +,and CD3-CD16+CD56+NK),there is no significant difference between the two groups.Noted that the expression of TIM3 on CD3+CD8+ T cells(10.22±4.90 vs.7.81±2.44,P = 0.078)and PD-L1 on CD14+ monocytes(7.89±9.33 vs.3.56±2.49,P=0.079)were showed an upward trend in patients with MDD than in HCs.Conclusions:1.Elevated plasma level of IL-6 was confirmed in patients with MDD in this study,approving that the abnormality of pro-inflammatory cytokines was associated with the onset of depression.2.The expression of TIM-3 on CD3+CD8+ T cells and PD-L1 on CD 14+monocytes were showed an upward trend in patients with MDD,which showed that immune checkpoints may play a role in the pathogenesis of depression.3.The number of T cell subsets has not been detected in this study.4.In the whole,the phenomenon that neuro-immune dysfunction exists in patients with major depressive disorder was supported in this study In the future,more focus could be paid on the possible effect of immune checkpoint inhibitors in the mechnism of MDD.