IFNA1 and Alzheimer disease: Based on expression of these functional markers, and consistent with observations from single cell RNAseq studies of Alzheimer’s disease [16], we described 5 subtypes of microglia including: (1) homeostatic, (2) proliferating, (3) phagocytic, (4) type I interferon responding (IFN) and (5) antigen presenting (MHC).