The heatmap showed that CD8+ T cells and neutrophils exhibited significantly different proportions among the three clusters, including a high proportion of CD8 or neutrophils, an intermediate proportion of CD8 or neutrophils, and a low proportion of CD8 or neutrophil clusters (Figure 2E), indicating differentially expressed IICs between MDD samples, especially CD8+ T cells and neutrophils. This evidence concerns the gene CD8A and major depressive disorder.