Several of the genetic loci associated with AD risk contain genes with known roles in inflammation, the complement system and the immune response in general (ABCA7, CLU, CR1, MS4A4E/MS4A6A, CD33, EPHA1, HLA-DRB5, HLA-DRB1, INPP5D, MEF2C and TREM2). Here, CD33 is linked to Alzheimer disease.