MDD Pts had significantly decreased level of plasm IL-2, IFN-γ, TNF-α, and IL-10 compared to healthy controls; IL-2, IFN-γ, and IL-10 showed significant increases after 12 weeks treatment compared to before treatment. IFN-γ level was negatively correlated with the CDI (r = −0.377, p < 0.01) and HDRS score (r = −0.457, p < 0.01). This evidence concerns the gene IL2 and major depressive disorder.