GZMK and major depressive disorder: Interestingly, the expression levels of CXCR6, KLRG1, GZMK, EOMES, and GZMA were decreased in MDD patients, while they were upregulated in OA patients, and the expression levels of CXCL5, THBS1, ITGB5, ITGB3, and CLEC1B were increased in MDD patients, while they were downregulated in OA patients (Figure 3C).