INCLUSION CRITERIA:
Patients must have XSCID as defined by either a deleterious mutation in IL2RG, the absence of or less than 5% of normal detectable gc protein, or evidence of functionally defective gc protein.
Patients must be between 2 and 20 years of age.
Patients must weigh at least 15 kg.
Patients will have evidence of combined B-cell and T-cell immune deficiency over at least a 6 month period despite previous allogeneic BMT at least 18 months prior to study entry. T-cell immune deficiency is defined as one or more of the following: Total T-cell count less than 500/ul; less than 50% of normal value for in vitro mitogen stimulation; or absent proliferation in vitro to antigens. B-cell immune deficiency is defined as one or more of the following: IgM, IgA or IgE values which are 2 or more standard deviations below the established value for normal, IgG values falling to less than 30% of normal during unintended interruptions or delay in the periodic administration of IVIG; or documented failure to respond to a specific antigen challenge.
Patients must less than or equal to 3% of their mobilized CD34+ cells deriving from their allogeneic bone marrow donor.
EXCLUSION CRITERIA:
Any current or preexisting hematologic malignancy.
Current treatment with any chemotherapeutic agent.
Current treatment with any immunosuppressive agent, excluding corticosteroids.
Documented HIV-1 infection.
Documented Hepatitis B infection.
Childhood malignancy (occurring before 18 years of age) in the patient or a first degree relative, or known genotype of the subject conferring a predisposition to cancer.