ERAP1 and Alzheimer disease: We described the contributions of several new genes to AD: a protective effect of the KIR2DS1 gene encoding an activating receptor expressed on the surface of natural killer cells and some T lymphocytes [18]; a protective effect of the HLA-C*05:01 allele [11]; an association of the C allele of the single nucleotide polymorphism (SNP) rs26618 in the ERAP1 gene T lymphocytes [11]; an effect of the rs26618 on the enzymatic activity of ERAP1 [11]; and synergism of ERAP1 and ERAP2 effects on AD risk [19].