CR1, encoding complement receptor 1 (CR1/CD35) (Harold et al., 2009; Lambert et al., 2009) and CLU, encoding the plasma complement inhibitor clusterin (Lambert et al., 2009), are top GWAS hits in AD, while C1S, encoding the complement enzyme C1s, was recently implicated in AD GWAS (Bellenguez et al., 2022). This evidence concerns the gene C1S and Alzheimer disease.