Effects of Irradiation on PHA-Induced T-Lymphocyte Colonies: Differential Effects According to the Timing of Irradiation

Abstract

To investigate the effect of irradiation on [human] lymphocyte mitosis a T-lymphocyte colony assay was used; this sensitive technique avoided the methodological problems associated with previous techniques such as 3H-thymidine uptake. Irradiation doses in the range of 0.5-4 Gy [gray] had the effect of decreasing the lymphocytes'' capacity to divide as shown by their reduced T-colony forming ability. This radiosensitivity varied according to the timing of irradiation in relation to the stage of colony growth. The colony-forming cells could withstand higher irradiation doses without losing their replicative ability when they were irradiated prior to or during early stages of PHA [phytohemagglutinin] stimulation. A similar protection by PHA stimulation has been well documented for nondividing T-lymphocyte functions but, due to the lack of a suitable methodology, had hitherto not been described for dividing T-lymphocytes. The early events associated with PHA stimulation might lead to an improved ability of T-lymphocytes to withstand higher doses of irradiation before mitotic death is registered.