CR1 and Alzheimer disease: Accordingly, components of innate immunity and complement cascade have been considered risk factors for the development of AD and have been associated with abnormal clearing or deposition of Aβ; in particular, variants in the genes complement receptor 1 (CR1) (Zhu et al., 2015), CD33 (Walker et al., 2015), and TREM2 (Yeh et al., 2016).