Mutations in Foxp3 are responsible for the scurfy (sf) mutant mouse and for the autoimmune human diseases including the X-linked fatal “immune dysregulation, polyendocrinopathy, enteropathy, X-linked” (IPEX), autoimmune colitis, and RA [128]. The gene discussed is FOXP3; the disease is immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.