RADIATION-INDUCED APOPTOSIS IN HUMAN-LYMPHOCYTES - POTENTIAL AS A BIOLOGICAL DOSIMETER

We have tested the possibility of using apoptosis (programmed cell dea th) in human peripheral blood lymphocytes as a short-term biological d osimeter. Lymphocytes isolated from whole blood were irradiated in cul ture with 250 kVp x-rays or Co-60 gamma rays, Two assays mere used to measure apoptosis in lymphocytes after irradiation: ill situ terminal deoxynucleotidyl transferase assay and fluorescence analysis of DNA un winding assay, Similar qualitative and quantitative results were produ ced by the assays, supporting the notion that the fluorescence analysi s of DNA unwinding assay measured DNA fragmentation associated with ap optosis. Induction of apoptosis in lymphocytes irradiated in vitro was proportional to dose and could be detected following exposures as low as 0.05 Gy, Lymphocytes from individual donors had reproducible dose responses, There was, however, variation between donors, X-ray and gam ma-ray exposures induced similar levels of apoptosis at similar doses. The induction kinetics of apoptosis in vitro indicate a maximum is re ached about 72 h after irradiation. In conclusion, the in vitro experi mental evidence indicates that radiation-induced apoptosis in human ly mphocytes has the kinetics, sensitivity, and reproducibility to be a p otential biological dosimeter.