FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: The involvement of Tregs was initially suggested by the analysis of immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) patients who suffer from FOXP3 deficiency and showed elevated frequencies of circulating autoreactive mature naive B cells in the absence of functional Tregs (20).