FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: The importance of Tregs was elucidated using mice and human forkhead box p3 (Foxp3) gene mutation studies; human IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome, caused by Foxp3 mutation, induces early onset of T-cell-dependent lymphoproliferation with cytokine storm [9–12].