IL2RA and Autoimmunity: Surprisingly, the lack of spontaneous autoimmunity was not reflected in the in vitro Treg cell suppression assay, which revealed a strong dependency on IL-2R signaling for Treg cell suppressive function in vitro, as previously suggested.9,10 This observation indicates that commonly used in vitro coculture suppression assays more likely mimic the requirements for Treg cell function in inflammatory states than in steady-state situations.