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 cardiac, renal, pulmonary, liver, or hematologic 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