Inclusion criteria : * Boys diagnosed during the first year of life * Diagnosis of classical SCID-X1 based on immunophenotype (absent, or reduced numbers of non-functional T lymphocytes) and confirmed by DNA sequencing * No HLA identical family donor and no HLA identical unrelated donor (10/10 antigens) found in the 6 weeks following the beginning of the search. This period could be shortened if the probability to find a donor is low or if the clinical situation (gravity) required * Presence of a severe infection: pneumonitis and / or chronic diarrhea, or infection with herpes viruses or parainfluenza type 3 or adenovirus, or disseminated BCG infection, or presence of severe diarrhea and a severe compromise of the general state with denutrition * Or failure of a HLA HAPLO-identical bone marrow transplant within 10 years after transplantation * In all cases: * No family background of cancer in childhood. * No cytogenetic abnormalities (medullary karyotype) and no detection of main rearrangements associated with acute leukemia of children * Parental/guardian voluntary consent Exclusion criteria : * Atypical health with autologous T\> 500/ml3 * Infection by HIV 1 or 2 * Allogeneic HSC completed (excluding situations of failure) * Existence of an HLA identical family donor or HLA identical unrelated donor * No severe infections in a child with a preserved general state * Family background of cancer in childhood * Detection of cytogenetic abnormality and / or rearrangement associated with acute leukemia of children * No affiliation to a social security scheme (beneficiary or assignee)