IL2 and Autoimmunity: Indeed, IL-2 signals seem to be pivotal for Treg survival because animals that lack IL-2, CD25, or CD122 are largely devoid of peripheral Treg and suffer from severe autoimmunity (Sadlack et al., 1993; Suzuki et al., 1995; Willerford et al., 1995; Fontenot et al., 2005).