Although TREM2 is well known to be involved in phagocytosis and removal of apoptotic neurons (Takahashi et al, 2005; Colonna et al, 2007; Hsieh et al, 2009), the pathological consequences of a TREM2 loss of function in the context of AD pathogenesis are highly controversial. Here, TREM2 is linked to Alzheimer disease.