Controversial effects of increased expression of TREM2 protein were correlated with either apoptosis and decreased synaptic communication in Alzheimer's disease (AD) patient samples (Lue et al., 2015), or with an increased microglia ability to phagocytose, to inhibit Aβ proinflammatory responses and to rescue spatial cognitive impairment in the AD mouse model (Jiang et al., 2014). Here, TREM2 is linked to Alzheimer disease.