Identification of a novel variant in FOXP3 associated with IPEX syndrome. (A) Sequence of the FOXP3 gene in the IPEX patient. (B) FOXP3 expression in Tregs (CD4⁺CD25^hi) and T_naive (CD4⁺CD25⁻) from the IPEX patient and healthy control shown by flow cytometry (left) and histogram the mean fluorescence intensity (right). (C) In vitro suppression assay using Tregs from a healthy control or IPEX patient and carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled allogeneic responder T cells.