Comparison of the distribution of progenitor cells in G-CSF-mobilized peripheral blood and steady-state bone marrow after counterflow centrifugal elutriation

Blood-derived progenitor cells obtained following mobilization with granulocyte colony-stimulating factor (MoPBSC) are increasingly being used as an alternative to bone marrow (BM) in allogeneic stem cell transplantation. The higher numbers of mature T lymphocytes in MoPBSC grafts may increase the risk of (chronic) graft-vs.-host disease. Counterflow centrifugal elutriation (CCE) is an effective method for T-cell depletion of BM grafts. The elutriation characteristics of steady-state BM and MoPBSC were compared using a CCE procedure in which fractions were obtained after small incremental increases in flow rate with constant centrifugal force. Counterflow centrifugal elutriation experiments with MoPBSC from six healthy volunteers showed that 54% of all cells collected were recovered in the ≤15 mL/minute fractions, whereas experiments with mononuclear BM cells from five healthy volunteers resulted in recovery of 52 % of collected cells from the ≥19 mL/minute fractions. The peak concentrations of CD34⁺ cells were found in the same fraction (18 mL/minute), but more CD34⁺ cells from MoPBSC were recovered from the small (≤16 mL/minute) fractions (54% for MoPBSC, 26% for BM; p=0.08). The small CD34⁺ cells from BM were more frequently lacking CD38 and human leucocyte antigen-DR expression than the small CD34⁺ cells from MoPBSC. Mature T-cells (CD3⁺) in BM and MoPBSC samples had similar CCE features, as did early (long-term culture initiating cells, high-proliferative potential colony-forming cells) and more mature (colony-forming units granulocyte/macrophage, BFU-e) hematopoietic progenitor cells. The results of this study suggest that T-cell depletion by CCE of MoPBSC as compared to BM products, may lead to a greater loss of CD34⁺ cells, but not of immature hematopoietic progenitor cells.