The critical role of IL-2 in immune homeostasis was already evident from early studies that demonstrated that the deletion of the IL-2 gene in mice resulted in the development of autoimmune disease, in particular ulcerative colitis.[8] Autoimmune manifestations were also observed in mice deficient of the genes that encode for the IL-2 receptor α-chain (CD25) and β-chain (CD122).[9]. The gene discussed is IL2; the disease is ulcerative colitis.