Collection of pluripotential hematopoietic stem cells by cytapheresis

Successful complete hematopoietic reconstitution (CHR) using nonleukemic peripheral stem cells (PSC) after marrow ablation has been reported in animals but not man. Previous studies of cytapheresis products from humans, as a prelude to use for CHR, have documented the presence of committed myeloid (CFU-GM) and erythroid (BFU-E) precursors. We have examined mononuclear cell (MNC) products collected on the Fenwal CS3000 Blood Cell Separator for these plus the more primitive mixed (granulo-, erythro-, mono-, and megakaryocytic) cell colony-forming units (CFU-GEMM) and for various lymphocytic subpopulations (LSP). One to two-hour products contained 36 ± 7 CFU-GEMM/10⁶ MNC (mean ± SE, n = 8) or 490 ± 131/ml product. This compared favorably with blood (23 ± .4/10⁶ MNC or 46 ± 8/ml, n = 14) and bone marrow (146 ± 58/10⁶ MNC, n = 12). Collection efficiency for E-rosette-positive cells approximated that for total lymhocytes and was variable for other LSP. Recovery of CFU-GEMM after freezing in 10% dimethylsulfoxide at a controlled rate and storage in liquid N₂ was 54% ± 8% (n = 8). Cytapheresis collection of large numbers of pluripotent hematopoietic precursors and demonstration of adequate recovery of these after cryopreservation, both previously unreported, are significant steps toward eventual CHR using nonleukemic PSC.