In a seeding model involving intracerebral injection of Aβ-rich brain extracts from AD patients or aged APP mice, the absence of TREM2 resulted in an increased number of seeded amyloid plaques with reduced levels of microglia-derived ApoE deposition within the plaques in mouse brains (Parhizkar et al., 2019). Here, TREM2 is linked to Alzheimer disease.