Radiation effects on lymphohematopoietic colonies: existence of subpopulations of lymphocyte progenitors with differing radiosensitivities and evolution of radioresistant subpopulations in response to continuous irradiation in beagles

In vitro dose-response relationships were studied for x-irradiation in beagles using a methylcellulose culture system which allows for the growth of T-lymphocyte colonies in response to mitogenic stimulation of peripheral blood lymphocyte by PHA and con-A. The best fit for the resultant survival curves was biexponential indicating the existence of subpopulations of T-lymphocyte progenitors with varying degrees of radiosensitivity. Studies performed on blood obtained from beagles receiving continuous irradiation demonstrated an increased survival for the con-A response but not for PHA. These results demonstrate the evolution of radioresistant con-A responsive T-lymphocyte progenitor in response to continuous irradiation and imply that the target cells for PHA and con-A represent distinct subpopulations of T-lymphocytes