Technical Report No. 15-89
Is variation in human radiosensitivity real or artifactual? A study by colony formation method using peripheral blood T-lymphocytes
Nakamura N, Kushiro J, Sposto R, Akiyama MEditor’s note: Publications based on this report were published in Mutat Res 234:15-22, 1990, and Radiat Res 125:326-30, 1991.
Summary
Two methods of producing human T-lymphocyte colonies in vitro are described, as well as dose-survival experiments using these methods for the investigation of possible differential radiosensitivity among individuals. In one method, the cloning efficiency (CE) of nonirradiated lymphocytes was between 10% and 40% (method 1), whereas subsequent improvement in assay conditions (method 2) resulted in a CE greater than 30%. In vitro X-irradiation of colonies produced using method 1 revealed that the dose required to kill 90% of the cells (D10) was 2.87 plus or minus 0.28 Gy (mean plus or minus SD, n = 18) for repeated examinations of lymphocytes from one reference individual. Using method 2, the D10 values were greater, viz., 3.66 plus or minus 0.21 Gy for 28 repeated tests of the same reference individual and 3.58 plus or minus 0.19 Gy for 31 different individuals. Analysis of variance to compare the data from repeated examinations of one person versus data from single examinations of different persons showed that variation in the D10 value was not significantly greater in the latter group. These results support the hypothesis that individual variation in human radiosensitivity is quite small, if it exists at all, as far as can be determined by the loss of colony-forming ability of irradiated G0 lymphocytes.
Two methods of producing human T-lymphocyte colonies in vitro are described, as well as dose-survival experiments using these methods for the investigation of possible differential radiosensitivity among individuals. In one method, the cloning efficiency (CE) of nonirradiated lymphocytes was between 10% and 40% (method 1), whereas subsequent improvement in assay conditions (method 2) resulted in a CE greater than 30%. In vitro X-irradiation of colonies produced using method 1 revealed that the dose required to kill 90% of the cells (D10) was 2.87 plus or minus 0.28 Gy (mean plus or minus SD, n = 18) for repeated examinations of lymphocytes from one reference individual. Using method 2, the D10 values were greater, viz., 3.66 plus or minus 0.21 Gy for 28 repeated tests of the same reference individual and 3.58 plus or minus 0.19 Gy for 31 different individuals. Analysis of variance to compare the data from repeated examinations of one person versus data from single examinations of different persons showed that variation in the D10 value was not significantly greater in the latter group. These results support the hypothesis that individual variation in human radiosensitivity is quite small, if it exists at all, as far as can be determined by the loss of colony-forming ability of irradiated G0 lymphocytes.