Hematopoietic stem cell transplantation for severe combined immune deficiency or what the children have taught us.

It is now more than 40 years since the first successful allogeneic hematopoietic stem cell transplantation (HSCT) for a child with severe combined immunodeficiency (SCID). In the succeeding years, HSCT for SCID patients have represented only a small portion of the total number of allogeneic HSCT performed. Nevertheless, the clinical and biologic importance of the patients transplanted for SCID has continued. SCID patients were the first to be successfully transplanted with nonsibling related bone marrow, unrelated bone marrow, T-cell depleted HSCT, and genetically corrected (gene transfer) autologous HSC. Many of the biologic insights now widely applied to allogeneic HSCT were first identified in the transplantation of SCID patients. This article reviews the clinical and biologic lessons that have been learned from HSCT for SCID patients, and how the information has impacted the general field of allogeneic HSCT.