FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: Expression of the transcription factor Foxp3 is a prerequisite for their suppressive activity, since patients carrying mutations altering the expression or function of Foxp3 may develop IPEX (Immunodysregulation polyendocrinopathy enteropathy X-linked syndrome, a severe autoimmune disease [2].