The encoding gene of p35 subunit, IL-12A, is located on chromosome 3q25.33, and several IL-12A polymorphisms were associated with the susceptibilities to primary biliary cirrhosis (PBC), Graves’ disease and Alzheimer’s disease [29,30,31]; EBI3, the encoding gene of another subunit, EBI3, is located on chromosome 19q13.3, and the polymorphisms of EBI3 rs428253, rs4740 and rs4905 were associated with the decreased risk of developing ulcerative colitis (UC) [32]. Here, IL12A is linked to Alzheimer disease.