Mutations in the human FOXP3 gene causes the disease Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked syndrome (IPEX) [5], and the Foxp3 mutant Scurfy mouse model displays a similar pathology involving dysregulated CD4+ T cell infiltration and activation [6]–[8]. Here, FOXP3 is linked to polyendocrinopathy.