CHARACTERIZATION OF CD34-BLOOD CELLS FROM HEALTHY-ADULTS MOBILIZED BYRECOMBINANT HUMAN GRANULOCYTE-COLONY-STIMULATING FACTOR( PERIPHERAL)

Primed peripheral blood hematopoietic stem cells (PBSC) generate and s ustain lymphohematopoiesis in myeloablated animals, and recent reports indicate that allogeneic transplantation using PBSC grafts may be fea sible in humans. A major concern with the use of PBSC transplants is t hat permanent engraftment may be limited because of lack of sufficient numbers of primitive progenitor cells in the graft. In the present st udy, in vitro colony formation and immunophenotype of CD34(+) cells in PB of healthy adults during short-term granulocyte colony-stimulating factor (G-CSF) administration were compared with that of CD34(+) cell s in normal bone marrow (BM). The number of CD34(+) cells mobilized to PB peaked at day 4 or 5 of G-CSF administration. The phenotypic profi le of CD34(+) PB cells showed a substantial increase in the percentage of CD34(+)CD13(+) and CD34(+)CD33(+) cells (myeloid progenitors) and a corresponding decrease in the percentage of CD34(+)CD10(+) and CD34( +)CD19(+) cells (B lymphoid progenitors) compared with CD34(+) BM cell s. The other subsets studied, including CD34(+)CD38(-) and CD34(+)HLA- DR(-) cells, were present in both compartments in similar proportions. Furthermore, primed CD34(+) PB cells were enriched for colony-forming cells (CFC) and displayed an increased clonogenicity when compared wi th their counterparts in BM. A comparison between a postulated PBSC gr aft and an average BM graft is presented, showing that such PBSC graft s will be enriched for CD34(+) cells as a whole, CD34(+)CD33(+) cells, and colony-forming cells (CFC), factors which have been shown to corr elate to acceleration of hematologic reconstitution and reduction in r equirements for supportive care in autografting. Hence, we predict tha t allogeneic transplantation using G-CSF-primed PBSC grafts will resul t in a more rapid hematologic reconstitution after myeloablative condi tioning than BM grafting. The question of whether PBSC allografting wi ll result in permanent engraftment and clinical benefits as observed i n autografting has to be determined in prospective clinical studies. ( C) 1994 by The American Society of Hematology.