Response of Human Bone Marrow Progenitor Cells to X-rays in Vitro

SummaryIn 25 out of 33 cases the survival response of myeloid progenitor cells from fresh human bone marrows, X-irradiated in vitro in phosphate-buffered saline at 23°C, was characterized by a two-term exponential relationship, with D0 values of 0·42 ± 0·19 Gy and 1·38 ± 0·37 Gy, respectively. In the remaining eight cases for which the colony-forming efficiency was 10 times lower, survival followed a single exponential function with D0 = 1·18 ± 0·15 Gy. The biphasic response at 23°C became a single exponential response when the temperature at irradiation was 30 or 37°C.