The HLA-DRA and HLA-DRB5 genes are members of MHC class II, a highly polymorphic region involved in the immune response and histocompatibility; both of these genes are predominantly expressed by microglia in the brain and might play a role in susceptibility to AD (Zhang et al., 2015; Villegas-Llerena et al., 2016; Yokoyama et al., 2016). Here, HLA-DRA is linked to Alzheimer disease.