MIXED HEMATOPOIETIC COLONY FORMATION VIA IMMATURE BLAST CELL CLUSTERSON FETAL MESENCHYMAL CELL-LAYERS DISTINGUISHES STEM-CELLS FROM PERIPHERAL-BLOOD, CORD-BLOOD, BONE-MARROW AND BLOOD STEM-CELLS MOBILIZED BY GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR

Multilineage colony formation was evaluated from healthy donors' bone marrow (BM), peripheral blood (PB) and cord blood (CB) and compared wi th blood stem cell (BSC) harvests of sarcoma patients mobilized with g ranulocyte-macrophage colony-stimulating factor (GM-CSF). The test was a modified CFU-blast assay performed with and without an irradiated f oetal mesenchymal cell layer (HFFF). These non-transformed mesenchymal cells served as a good source of haematopoietically active stroma cel ls in that cytokine expression patterns (interleukin (IL)-6, granulocy te (G)-CSF, GM-CSF) and adhesion molecules on HFFF cells were qualitat ively identical to BM-derived fibroblasts, but the expression density of adhesion receptors was significantly higher. This HFFF layer stimul ated blood stem cells of GM-CSF-treated patients significantly more th an a cocktail of exogenous growth factors with IL-1, IL-6, and stem ce ll factor (SCF). The reverse was true for multilineage colonies from h ealthy donors' PB, BM, and CB. According to these results, stem cells of GM-CSF-treated patients are functionally distinct due to their depe ndence on stroma-derived factors and/or matrix-adhesion interactions a nd can be reproducibly evaluated on these mesenchymal cells.