IL-2−/−, IL-2Rα−/−, or IL-2Rβ−/− KO mice have decreased numbers of natural CD4+CD25+ Tregs [26], [27], [28], [29] and suffer from autoimmunity [30], [31], [32] or fatal lymphoproliferative disease [29]. The gene discussed is IL2RB; the disease is Autoimmunity.