The importance of Foxp3 has been demonstrated by mutations in the foxp3 gene that result in the loss of Treg cell function and the development of multi-organ autoimmunity, including autoimmune diabetes, in IPEX patients and Scurfy mice (Hori et al., 2003; d’Hennezel et al., 2012). Here, FOXP3 is linked to immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.