APOE and Alzheimer disease: AD2-microglia possibly have neurotrophic functions.15 Besides, Nguyen et al. characterized microglia in various states in AD brains: homeostatic microglia, amyloid responsive microglia, dystrophic microglia, and motile microglia, among which the amyloid responsive microglia relied on triggering receptor expressed on myeloid cells-2 (TREM2) and APOE signaling.144 Another study used snRNA-seq to comprehensively characterize transcriptomes in microglia nuclei isolated from neuropathologically defined AD and control brains with a range of Aβ and phosphorylated (p)-Tau pathology.