RADIOSENSITIVITY INCREASES WITH DIFFERENTIATION STATUS OF MURINE HEMATOPOIETIC PROGENITOR CELLS SELECTED USING ENRICHED MARROW SUBPOPULATIONS AND RECOMBINANT GROWTH-FACTORS

The radiosensitivity of populations of colony-forming cells (CFC) in murine bone marrow was investigated using different recombinant colony-stimulating factors (CSFs; murine IL-3 and granulocyte-macrophage CSF and human granulocyte CSF), or purified murine macrophage CSF. With unfractionated normal bone marrow the CFC increased in radiosensitivity as they progressed through the granulocyte lineage. The D0 values ranged from 129 ± 12 cGy for CFC stimulated with GM-CSF down to 42 ± 2 cGy after stimulation with G-CSF. IL-3 stimulated a CFC population which gave the only survival curve with a shoulder (n = 1.9 ± 0.3). With semipurified populations of primitive or bipotential CFC, D0 values were generally lower with respect to the equivalent values for unpurified bone marrow (range 62 ± 7 cGy to 135 ± 7 cGy). Changes in cluster/colony ratio and colony morphology together possibly with products of accessory cells influence the interpretation of the radiosensitivity parameters.