ABSTRACT
Severe combined immunodeficiency due to adenosine deaminase deficiency (ADA-SCID) results from accumulation of the toxic purine metabolites, deoxyadenosine (dAdo) and its triphosphate form, dATP. Toxic levels of dATP cause a depletion of circulating Τ and Β cells (Hershfield and Mitchell, 1994.) The clinical course of ADA-SCID is characterized by severe lymphopenia, impaired cellular and humoral immune responses, and recurrent infections, usually from opportunistic organisms, which are often fatal. Allogeneic bone marrow transplantation using an HLA-matched donor is the treatment of choice for ADA-SCID with a ~70% cure. However, only 20-30% of children with SCID will have an HLA-matched donor, and bone marrow transplantation using T-cell-depleted haplo-identical donors (i.e., parents) is much less successful (O'Reilly et al., 1989·)
