Thus, the in vivo lack of Treg function could be explained by the decreased production of IL-2 by Teff in these IPEX patients [3], [34].Altogether, this suggests that in humans IL-2 is very important for Treg function, but is not required for Teff survival and function, as these Teff, despite low IL-2 production, are still highly activated and causing disease. The gene discussed is IL2; the disease is immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.