Size and density characterization of human committed and multipotent hematopoietic progenitors.

Physical characterization of human blood and bone marrow (BM) hematopoietic precursors is necessary for the design of adequate techniques to isolate these cells for experimental and possible clinical use. Elutriation and continuous Percoll gradient were used to define the size and density of committed (CFU-GM, BFU-E, and CFU-E) and multipotent (CFU-MIX) progenitors on paired BM and blood samples from normal donors. Cells were initially prepared over Ficoll-Hypaque (specific gravity 1.077 g/cm3). Elutriation was performed on a Beckman JE-6B rotor with a standard chamber at 2000 rpm using flow rates of 7-23 ml/min. Percoll gradients were centered at 1.070 g/cm3 using ultracentrifugation. Cell density was determined using marker beads. Density was slightly higher for BM than for blood progenitors of the same class. Progenitor sizes (proportionate to elutriation flow rate) were similar in BM and blood. CFU-MIX, BFU-E, and CFU-GM coseparated in blood and BM; CFU-E (BM) were larger and more dense than other BM progenitors. BM and blood E-rosette-positive cells were separated more effectively by size than by density. The similarity in size and small differences in density between blood and BM progenitors may allow adaption of blood separation techniques (apheresis) to processing of BM for cryopreservation and/or in vitro treatment. Similarly, the ability to separate T cells from progenitors in blood by elutriation (albeit only partially), as has been described for BM, may help in the modification of existing apheresis techniques to achieve such separations.