A COMPARATIVE-STUDY OF THE PHENOTYPE AND PROLIFERATIVE CAPACITY OF PERIPHERAL-BLOOD (PB) CD34(-PHASE PB AND BONE-MARROW CD34(+) CELLS() CELLS MOBILIZED BY 4 DIFFERENT PROTOCOLS AND THOSE OF STEADY)

Peripheral blood (PB) CD34(+) cells from four commonly used mobilizati on protocols were studied to compare their phenotype and proliferative capacity with steady-state PB or bone marrow (BM) CD34(+) cells. Mobi lized PB CD34(+) cells were collected during hematopoietic recovery af ter myelosuppressive chemotherapy with or without granulocyte-macropha ge colony-stimulating factor (GM-CSF) or granulocyte colony-stimulatin g factor (G-CSF) or during G-CSF administration alone. The expression of activation and lineage-associated markers and c-kit gene product we re studied by flow cytometry. Proliferative capacity was measured by g eneration of nascent myeloid progenitor cells (granulocyte-macrophage colony-stimulating factor; CFU-GM) and nucleated cells in a stroma-fre e liquid culture stimulated by a combination of six hematopoietic grow th factors (interleukin-1 (IL-1), IL-3, IL-6, GM-CSF, G-CSF, and stem cell factor). G-CSF-mobilized CD34(+) cells have the highest percentag e of CD38(-) cells (P < .0081), but otherwise, CD34(+) cells from diff erent mobilization protocols were similar to one another in their phen otype and proliferative capacity. The spectrum of primitive and mature myeloid progenitors in mobilized PB CD34(+) cells was similar to thei r steady-state counterparts, but the percentages of CD34(+) cells expr essing CD10 or CD19 were lower (P < .0028). Although steady-state PB a nd chemotherapy-mobilized CD34(+) cells generated fewer CFU-GM at day 21 than G-CSF-mobilized and steady-state BM CD34(+) cells (P < .0449), the generation of nucleated cells and CFU-GM were otherwise comparabl e. The presence of increased or comparable numbers of hematopoietic pr ogenitors within PB collections with equivalent proliferative capacity to BM CD34(+) cells is not unexpected given the rapid and complete he matopoietic reconstitution observed with mobilized PB. However, all fo ur types of mobilized PB CD34(+) cells are different from steady-state BM CD34(+) cells in that they express less c-kit (P < .0002) and CD71 (P < .04) and retain less rhodamine 123 (P < .0001). These observatio ns are novel and suggest that different mobilization protocols may act via similar pathways involving the down-regulation of c-kit and may b e independent of cell-cycle status. (C) 1994 by The American Society o f Hematology.