For example, a loss-of-function mutation in the essential regulator of Tregs, the forkhead box transcription factor Foxp3, leads to a lethal autoimmune and inflammatory disorder in the “scurfy” mouse and the IPEX syndrome (Immune dysregulation Polyendocrinopathy Enteropathy X-linked Syndrome) in humans (Fontenot and Rudensky, 2005; Chatila, 2009). Here, FOXP3 is linked to immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.