The autoimmune targets in IPEX are dominated by gut epithelial proteins

Regulatory T (Treg) cells play a key role in immune system homeostasis by suppressing detrimental immune responses against self-proteins, in particular in the intestine.1 Patients with mutations in the gene FOXP3 display a severe defect of Treg-cell function that results in IPEX syndrome (OMIM 304790) characterized by impaired immune tolerance and multiorgan autoimmunity. Dermatitis, type 1 diabetes, and in particular autoimmune enteropathy are hallmarks of the syndrome. Intestinal Treg cells normally suppress immune responses against harmless dietary antigens and commensal microorganisms, but the intestinal self-proteins that are guarded by Treg cells have not yet been fully identified.