Single leukapheresis products collected from healthy donors after the administration of granulocyte colony-stimulating factor contain tenfold higher numbers of long-term reconstituting hematopoietic progenitor cells than conventional bone marrow allografts

Cytokine-mobilized peripheral blood progenitor cells (PBPCs) have been used successfully for hematopoietic reconstitution following allogeneic transplantation. The ease of harvest, the faster engraftment and the high yield of CD34 super(+) cells have made this source of hematopoietic progenitor cells (HPCs) an attractive alternative to bone marrow (BM). In the present study we compared the engraftment potential of conventional BM allografts and single leukapheresis products (LPs) collected from healthy donors following the administration of granulocyte colony-stimulating factor (G-CSF). For this, lineage-committed and primitive HPCs were assessed by flow cytometry and by colony- and cobblestone area-forming cell (CFC, CAFC) assays. Mean numbers of CD34 super(+) cells in LPs (n = 11) were similar to that of BM grafts (n = 12) (278 plus or minus 57 vs 227 plus or minus 34 x 10 super(6) CD34 super(+) cells). The frequencies of CFCs, week 5 CAFCs and week 8 CAFCs were 1.6-, 8.4- and 10.3-fold higher in the CD34 super(+) compartment of mobilized blood than that of marrow, resulting in significantly higher yields of clonogenic HPCs in LPs when compared to BM grafts. We conclude that G-CSF preferentially mobilizes clonogenic progenitors capable of short- and, in particular, long-term reconstitution, and that the engraftment potential of single LPs is superior to that of BM allografts. Hence, the use of PBPCs may be favorable for protocols that include graft manipulations with expected cell loss (eg T cell depletion, CD34 super(+) selection). PBPCs may also be advantageous for gene therapy trials due to their high numbers of potential target cells (eg CAFCs).