The importance of FOXP3 in Tregs is supported by the evidence that mutations in the FOXP3 locus lead to Treg dysfunction and severe autoimmunity, as was first identified in Scurfy mutant mice (4) and the immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) in humans (5). This evidence concerns the gene FOXP3 and Autoimmunity.