FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: Tregs express FOXP3 as the most specific marker, and it has been shown that FOXP3-deficient individuals have severe autoimmune/autoinflammatory conditions, like immune dysregulation, polyendocrinopathy, enteropathy, and X-linked syndrome (IPEX) [76,77].