Our finding that a risk of AAA is associated with KIR3DL1Low alleles but not with the KIR3DL1 ligand, HLA-Bw4 (on HLA-A or HLA-B molecule), while the size of diameter of aneurism is associated with HLA-A-Bw4 but not with its receptor, KIR3DL1 (neither high nor low expressor allotype) needs explanation. The gene discussed is HLA-B; the disease is triple-A syndrome.