TREM2 and Alzheimer disease: TREM2 signaling is required for microglia to adopt a cell state referred to as “disease-associated microglia” (DAM), in which microglia may phagocytose Aβ, shield plaques, and delay tau pathology, suggesting a protective role of DAM in AD (Keren-Shaul et al, 2017; Deczkowska et al, 2018b; Kodama et al, 2020).