FOXP3 and polyendocrinopathy: First, we compared T1D Tregs from our cohort to Tregs from patients with a disease called Immune dysregulation, polyendocrinopathy, enteropathy X-linked syndrome (IPEX), which is caused by loss-of-function mutations in FOXP3. Tregs from children with T1D upregulated genes specific for defective Treg-like cells observed in IPEX patients66,67 (Fig. 5A).