FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: The importance of the transcription factor Foxp3 for controlling auto-immunity in humans is best exemplified in patients suffering from the IPEX (Immunodysregulation, Polyendocrinopathy, and Enteropathy, X-linked) syndrome, who develop a potentially lethal autoimmune syndrome and that carry mutations in the Foxp3 gene [4].