TREM2 and Alzheimer disease: Microglia in TREM2-deficient AD mice displayed less activation and did not engulf Aβ plaques. This impacts the density of Aβ plaques and promotes diffuse Aβ structures, which in turn are more neurotoxic, and contributes to the accumulation of classic AD pathology (Wang et al., 2016; Yuan et al., 2016).