PRIMITIVE HEMATOPOIETIC PROGENITOR CELLS ARE PRESENT IN PERIPHERAL-BLOOD AUTOGRAFTS

In this report we have used an in vitro assay for long-term culture-in itiating cells (LTC-IC) to detect primitive hematopoietic progenitor c ells (HPC) in the peripheral blood (PB) of cancer patients who receive d high-dose cyclophosphamide (HD-CTX) followed by a combination of rec ombinant hematopoietic growth factors (C-HGF) including either interle ukin-3 (IL-3) + granulocyte colony-stimulating factor (G-CSF), IL-3 granulocyte-macrophage colony-stimulating factor (GMCSF) or IL-3/GM-CS F fusion protein (PIXY-321). In addition, we have developed a quantita tive assay for cells capable of generating additional colony-forming c ells (pre-CFC) as a means of determining primitive HPC present in mobi lized PB cells, CD34(+) human leukocyte A (HLA)-DR(-) cells isolated f rom the mobilized PB were capable of initiating long-term hematopoiesi s in vitro that persisted for 10 weeks, while CD34(+) HLA-DR(-) cells obtained from the nonmobilized PB or BM were capable of sustaining lon g-term hematopoiesis in vitro for only 4 weeks and 8 weeks,, respectiv ely, As determined by a limiting dilution analysis of mobilized PB CD3 4 HLA-DR(-) cells, the frequency of pre-CFC was 4.3% (range, 1.0-8.3%) , Pre-CFC comprised 0.01% (range, 0.001-0.02%) of mobilized PB mononuc lear cells, and 151 pre-CFC were calculated to be present in one milli liter of mobilized PB (range, 20-310/ml), These results suggest that P B mononuclear cells collected by leukapheresis following mobilization with HD-CTX + C-HGFs contain not only differentiated HPCs but also mor e primitive HPC.