TREM2 and Alzheimer disease: In mouse AD models, TREM2 mediated clustering of microglia around β-amyloid plaques and activation of phagocytosis and the ‘proinflammatory’ response (Jay et al., 2015; Wang et al., 2015; Ulrich et al., 2018; Zhao et al., 2018; Zhong et al., 2018), and was required for the full expression of the response to Aβ pathology across all microglial modules (Friedman et al., 2018).