TREM2 and Alzheimer disease: Because AD risk genes APOE and TREM2 have been suggested to attenuate microglial responses to pathology, the effects of APOE and TREM2 on microglial phenotype, specifically ARM, were examined histopathologically in an expanded cohort of cases of neuropathologically defined AD versus non-AD tissues (Table S1) [14, 21, 22, 45, 46].