IL2RA/CD25, the gene for interleukin-2 receptor α, is emerging as a general susceptibility gene for autoimmune diseases because of its role in the development and function of regulatory T cells and the association of single-nucleotide polymorphisms (SNPs) within this gene with type 1 diabetes mellitus (DM), Graves' disease, rheumatoid arthritis (RA), and multiple sclerosis (MS). The gene discussed is IL2RA; the disease is autoimmune disease.