Effect of rhG-CSF on the mobilization of CD38 and HLA-DR subfractions of CD34+ peripheral blood progenitor cells.

Several studies have demonstrated that both CD34+/CD38- and CD34+/HLA-DR- human hematopoietic progenitor cells have properties associated with hematopoietic stem cells. However, the kinetics of these two cell populations in human peripheral blood (PB) after priming with granulocyte colony-stimulating factor (rhG-CSF) has not been investigated. By using flow-cytometric analysis we have shown that administration of rhG-CSF to 14 patients eligible for peripheral blood progenitor cell (PBPC) transplantation led to an increment of CD34+/CD38+ and CD34+/HLA-DR+ cells in the PB that paralleled the increase of total CD34+ cells, indicating that such subpopulations are responsible for the major release of CD34+ cells. Furthermore, rhG-CSF priming led to a significant mobilization of fractions of more immature CD34+/CD38- and CD34+/HLA-DR- cells to the PB. In the leukapheresis preparations, the average frequency of CD34+ cells lacking the CD38 or HLA-DR antigens was low (5% and 30%, respectively), with little overlap between the CD38- and HLA-DR- subpopulations. In addition, the yield of each subset of CD34+ cells (CD34+/CD38 +/- and CD34+/HLA-DR +/-) in the PB correlated with the numbers in the collected material. The results of the present study indicate that administration of rhG-CSF causes a significant increase of CD34+/CD38 +/- and CD34+/HLA-DR +/- cells in PB, and that such cells can be then safely harvested by leukapheresis procedures.