Successful human umbilical cord blood stem cell transplantation without conditioning in severe combined immune deficiency

A 2-month-old girl with severe combined immunodeficiency (SCID), presented with mild staphylococcal skin infection, lymphopenia, low T cell number, ab sence of B cells, high number of NK cells, and a negligible response to mit ogens, Since her older brother died as a result of SCID 2 years earlier, co rd blood was harvested from a sister born 2 1/2 years earlier, who was norm al and fully matched both by serology and molecular typing. In view of her clinical condition and in spite of a high number of NK cells with normal ac tivity, HUCBT without preparative conditioning was performed. No G-CSF was administered, Engraftment with mixed chimerism was evident 3 weeks post tra nsplantation. There were no peritransplantation complications, Eighteen mon ths post transplantation, the girl is in excellent condition, blood counts are normal, T cell engraftment is complete, B cell engraftment is proceedin g gradually, and the mitogen stimulation tests are normal, Due to the uniqu e nature of HUCB hematopoietic cells, engraftment without conditioning may be possible in patients with SCID with fully matched donors. This is the fi rst HUCBT performed without conditioning.