CD33 and Alzheimer disease: Notably, several Alzheimer’s disease (AD)-associated genetic risk variants—including APOE ε4, TREM2 R47H (rs75932628), CD33 rs3865444-C, INPP5D regulatory variants, MS4A6A locus variants, and PLCG2 P522R (rs72824905)—are enriched in microglia and influence their functional state (132).