Rapid Debulking and CD34 Enrichment of Filgrastim-Mobilized Peripheral Blood Stem Cells by Semiautomated Density Gradient Centrifugation in a Closed System

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Abstract
Filgrastim-mobilized peripheral blood progenitor cells (PBPC) are used for hematopoietic reconstitution after myeloablative therapy for malignancies, but the large number of cells collected in a single apheresis frequently presents a problem for storage or further processing. We have evaluated the use of CD34 Buoyant Density Solution-PBPC, an ultralight-density colloidal silica suspension, for debulking and enrichment of CD34+ cells in PBPC preparations in a semiautomated system. Cells were collected from four filgrastim-treated normal donors using the COBE Spectra. The separation procedure was carried out with Plasma-Lyte A and DNase 5 U/ml using the COBE 2991. Following processing and washing, there was a 26% recovery of nucleated cells, 2.6-fold enrichment of CD34+ cells, 68% recovery of CD34+ cells, 88% recovery of CFU-GM, 73% recovery of BFUE, 1 log depletion of CD3+ cells, 0.5 log depletion of CD56+ cells, and 1 log depletion of CD19+ cells. These results were not significantly different from those obtained when PBPC were separated over CD34 Buoyant Density Solution-PBPC by centrifugation in tubes. Using CD34 Buoyant Density Solution-PBPC, mononuclear preparations of PBPC can be enriched rapidly for CD34+ cells and depleted of lymphocytes in a semiautomated closed system using reagents produced according to good manufacturing practice (GMP).