This suggests that alterations in innate immune proteins, such as triggering receptor expressed by myeloid cells 2 (TREM2) and CD33, may increase the risk of developing AD (Naj et al., 2011; Bradshaw et al., 2013; Guerreiro et al., 2013; Jonsson et al., 2013). This evidence concerns the gene TREM2 and Alzheimer disease.