Various types of autoimmune diseases develop severely if humans and mice are deficient in molecules essential for Tregs, such as Foxp3, CTLA4, IL-2Rα (CD25), glucocorticoid-induced TNFR-related protein, T-cell immunoreceptor with Ig and ITIM domains, carbon catabolite repression 4, and PD-1 [33]. The gene discussed is IL2RA; the disease is autoimmune disease.