• Herbert Pichler, Volker Witt, Elisabeth Winter, Heidrun Boztug, Evgenia Glogova, Ulrike Pötschger, Susanne Matthes-Martin, and Gerhard Fritsch.
• Pediatric Hematology and Oncology, St. Anna Children's Hospital, Department of Pediatrics, Medical University of Vienna, Austria.
• Biol. Blood Marrow Transplant. 2014 May 1; 20 (5): 676-83.

AbstractAlthough the influence of transplanted bone marrow (BM) CD34+ cells on neutrophil engraftment (NE) and transplantation outcomes has been discussed controversially, thresholds between 2 and 4 × 10(6)/kg CD34+ cells are commonly accepted. This has substantial consequences for a donor in terms of BM volume to be collected, which frequently covers up to 15 to 20 mL/kg. As the BM CD34+ compartment contains varying fractions of CD34+/CD19+ B lymphoid progenitors, we tested the hypothesis that the infused CD34+/CD45dim/CD19-/CD10- myeloid stem cells might reliably predict NE in 94 children who received BM from 37 HLA-identical sibling donors (MSD) and 57 matched unrelated donors after myeloablative conditioning. The grafts contained a median of 3.6 × 10(6)/kg total CD34+ cells, which consisted of a median of 73% myeloid CD34+ cells and 27% B lymphoid progenitors. Grafts from donors <15 years old yielded significantly lower myeloid fractions compared with grafts from older donors (P < .001). All patients achieved sustained NE after median 20 (range, 11 to 40) days. By multivariate analysis, neither the number of total CD34+ cells (P = .605) nor of myeloid CD34+ cells (P = .981) correlated with NE, whereas transplantation from MSD (hazard ratio [HR] 3.51; P = .019) and the administration of granulocyte colony-stimulating factor (HR 2.24; P = .002) remained independent factors associated with earlier NE. Furthermore, neither total nor myeloid CD34+ cell quantities were associated with incidences of severe infections before NE (P = .271 and P = .132) or transplantation-related mortality (TRM) at day +100 (P = .294 and P = .490). Taking into account that the number of transplanted total CD34+ or myeloid CD34+ cells does not seem to have a relevant impact on time to NE, sepsis rates, or TRM, the need of certain threshold cell numbers should be revisited, at least for pediatric MSD.Copyright © 2014 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.

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