Granulocytopoietic precursor cells and regulatory factors in irradiated human bone marrow

The effects of irradiation on committed granulopoietic progenitor cells (CFU-C) and granulopoietic humoral regulators were studied in 17 X-ray treated patients with carcinoma of the breast or of the prostate. After 45 or 70 Gy, the CFU-C decreased to 14 ± 10% in irradiated areas. This remaining CFU-C population probably reflects a combination of radioresistance and survival in situ, and migration of CFU-C from protected marrow areas. The frequency of peripheral blood CFU-C did not change after irradiation. Endogenous colony stimulating activity (CSA), i.e., release of CSA within the marrow cell population, in post-irradiation bone marrow persisted on roughly the same level, indicating a fairly low radiosensitivity of the CSA-producing cells in the bone marrow. Colony stimulating activity in peripheral blood cells and serum remained unchanged, but there were great interindividual variations, and some of the patients with hypercellularity and CFU-C increase in nonirradiated marrow areas also had increased CSA. Serum lipoprotein inhibitors were higher in the post-treatment patients than in healthy control patients.