All patients were treated with myeloablative conditioning regimens, including hyper fractionated total body irradiation 1375 cGy over 4 days, followed by thiotepa 5 mg/kg/day i.v. for 2 days and either fludarabine 25 mg/m2/day i.v. for 5 days, or cyclophosphamide 60 mg/kg/day i.v. for 2 days; or busulfan followed by melphalan 70 mg/m2/day i.v. for 2 days, and fludarabine 25 mg/m2/day i.v. for 5 days. TCD of granulocyte colony-stimulating factor-mobilized PBSCs grafts was performed as described previously [8 (link), 9 (link)]. Ex vivo CD34+ selection of hematopoietic progenitor cells was performed using one of two methods as previously described: Isolex 300i Magnetic Cell Separator (Baxter, Deerfield, IL), followed by T cell rosetting with sheep erythrocytes (9 patients), or using the CliniMACS® CD34+ Reagent System (Miltenyi Biotech, Gladbach, Germany). All patients received either equine or rabbit anti-thymocyte globulin (ATG). Patients did not receive any other post-transplant immunosuppressive prophylaxis. All patients received supportive care and prophylaxis against opportunistic infections according to standard guidelines [10 (link)].