IL2 and Autoimmunity: IL-2 signaling also regulates immune tolerance, with Il2−/−, Il2ra−/−, and Il2rb−/− mice developing autoimmunity, while adoptive transfer of Treg cells into Il2rb−/− mice prevents autoimmunity, consistent with the nonredundant role of IL-2 in the development of Treg cells (18–23).