FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: Although 60–70% of patients with IPEX have mutations in FOXP3 and produced normal levels of IL-10 (18), other studies (19, 20) have described that certain IPEX patients lacked expression of CD25 (IL-2 receptor alpha chain) and showed defective IL-10 production after in vitro stimulation of their Tregs (20).