APOE and Alzheimer disease: Perhaps predictably, upregulation of genes transcripts involved in inflammatory processes and immune activation was identified in AD samples and included genes linked with higher risk of developing AD including TREM2 and PICALM. Other microglial genes that were upregulated overlapped with those identified in mouse models of AD (see below) including CD74, APOE, LPL, and complement and TLR family members, though species-specific differences were identified.