An increase in SPI1 (Fig. 5a), TYROBP (Fig. 5b), HLA-DRA (Fig. 5c), TREM2 (Fig. 5d), PTPRC (Fig. 5e), and AIF1 (Fig. 5f) was observed in AD tissue compared to neurologically normal controls, however, this may reflect an alteration in cell populations in the AD brain, including microglial proliferation or neuronal loss, as opposed to changes in individual microglia. Here, TREM2 is linked to Alzheimer disease.