The correlation analysis revealed that ALOX15B was positively associated with monocyte (r = 0.259, P = 0.003), MDSC (r = 0.218, P = 0.014), and macrophage (r = 0.180, P = 0.042), and negatively correlated with type 2 T helper cell (r = −0.334, P < 0.001), active CD4+ T cell (r = −0.306, P < 0.001), and gamma delta T cell (r = −0.199, P = 0.024) in MDD patients (Figure 6C and Supplementary Table 7). This evidence concerns the gene CD4 and major depressive disorder.