FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: The role of FOXP3 in regulating the suppressive function of human Tregs is exemplified by loss-of-function FOXP3 mutations, which result in primary Treg dysfunction and effector T cell (Teff) abnormalities, leading to the monogenic autoimmune disease, IPEX syndrome (5–10).