P2RY12 and major depressive disorder: The most abundant microglia cluster demonstrated significant differences between MDD and controls, as the levels of the core microglia markers purinergic receptor P2Y12 (P2RY12) and transmembrane protein 119 (TMEM119) were increased, whereas the levels of the HLA-DR and the activation marker CD68 were decreased in the MDD-derived microglia.