FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: Foxp3 is the master transcription factor (TF) involved in sustaining Treg suppressive identity and mutations leading to Foxp3 loss-of-function are associated clinically with the severe autoimmunity that presents as IPEX syndrome (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked) (4–6).