Inclusion Criteria: * Body weight greater than 8 kg, unless assessed as able to tolerate leukapheresis * FOXP3 gene mutation * Medical history of progressive symptoms of IPEX with persistency of some symptoms and/or signs requiring immune suppressive medication. The participant may or may not be on immunosuppression at time of starting the study. * Uncontrolled IPEX disease but unable to tolerate immune suppressive medication * Recurrent IPEX symptoms, requiring immune suppressive medications, in participants who have had prior allogeneic (allo) blood stem cell transplantation (HSCT). * ≥ 50% Performance rating on Lansky/Karnofsky Scale * Organ and marrow function within acceptable levels of function * Absence of ongoing infections * Must be able to consent if an adult Exclusion Criteria: * Medical instability * Less than 6 months life expectancy * Inability to meet limits for steroid dosing * Eligible for an HLA matched sibling or matched unrelated donor blood stem cell transplant, and be willing to undergo transplant. * Unrelated or comorbid disease * Allergy to any study medication, product, or intervention * Currently receiving another experimental treatment * History of malignancy, unless disease free for at least 2 years, with the exception of non melanoma skin cancer or carcinoma in situ