CD33 and Alzheimer disease: APOE is a key genetic risk factor for late-onset AD in the general population (Corder et al., 1993), and large genome-wide association studies (GWAS) carried out in recent years have identified further risk genes: CLU, PICALM, BIN1, CR1, ABCA7, CD2AP, EPHA1, CD33, and the MS4 locus (Harold et al., 2009; Hollingworth et al., 2011; Naj et al., 2011; Seshadri et al., 2010).