Harvesting and Enrichment of Hematopoietic Progenitor Cells Mobilized Into the Peripheral Blood of Normal Donors by Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) or G-CSF: Potential Role in Allogeneic Marrow Transplantation

To explore the use of stem/progenitor cells from peripheral blood (PB) for allogeneic transplantation, we have studied the mobilization of progenitor cells in normal donors by growth factors. Normal subjects were administered either granulocyte-macrophage colony-stimulating factor (GM-CSF) at 10 μg/kg/d, or G-CSF at 10 μg/kg/d, or a combination of G- and GM-CSF at 5 μg/kg/d each, administered subcutaneously for 4 days, followed by leukapheresis on day 5. Mononuclear cells expressing CD34 (CD34+ cells) were selectively enriched by affinity labeling using Dynal paramagnetic microspheres (Baxter Isolex; Baxter Healthcare Corp, Santa Ana, CA). The baseline CD34+ cells in peripheral blood before mobilization was 0.07% ± 0.05% (1.6 ± 0.7/μL; n = 18). On the fifth day after stimulation (24 hours after the fourth dose), the CD34+ cells were 0.99% ± 0.40% (61 ± 14/ μL) for the 8 subjects treated with G-CSF, 0.25% ± 0.25% (3 ± 3/μL, both P < .01 v G-CSF) for the 5 subjects administered GM-CSF, and for the 5 subjects treated with G- and GM-CSF, 0.65% ± 0.28% (41 ± 18/μL, P < .5 v GM-CSF). Parallel to this increase in CD34+ cells, clonogenic assays showed a corresponding increase in CFU-GM and BFU-E. The total number of CD34+ cells collected from the G-CSF group during a 3-hour apheresis was 119 ± 65 × 10s and was not significantly different from that collected from the group treated with G- and GM-CSF (101 ± 35 × 10s cells), but both were greater than that from the group treated with GM-CSF (12.6 ± 6.1 × 106; P < .01 for both comparisons). Analysis of the CD34+ subsets showed that a significantly higher percentage of cells with the CD34+/CD38- phenotype is found after mobilization with G- and GM-CSF. In the G-CSF group, immunomagnetic selection of CD34+ cells permitted the enrichment of the CD34+ cells in the apheresis product to 81% ± 11%, with a 48% ± 12% yield and to a purity of 77% ± 21% with a 51% ± 15% recovery in the G-and GM-CSF group. T cells were depleted from a mean of 4.5 ± 2.0 × 109 to 4.3 ± 5.2 × 106 after selection, representing 99.9% depletion. We conclude that it is feasible to collect sufficient numbers of PB progenitor cells from normal donors with one to two leukapheresis procedures for allogeneic transplantation. Subjects treated with the combination of G- and GM-CSF showed an equivalent mobilization of CD34+ cells and CFU-GM as G-CSF alone, and also demonstrated a significantly greater mobilization of cells with the CD34+/CD38 phenotype.