FLOW-CYTOMETRY AS A QUANTITATIVE AND SENSITIVE METHOD TO EVALUATE LOW-DOSE RADIATION-INDUCED APOPTOSIS IN-VITRO IN HUMAN PERIPHERAL-BLOOD LYMPHOCYTES

Human peripheral blood lymphocytes, irradiated In vitro, die by an apo ptotic process. The number of apoptotic cells after in vitro gamma-irr adiation (0, 0.1, 0.2, 1, 2 and 5 Gy) was measured by flow cytometry u sing Annexin V and DiOC(6) (a cationic dye) after 24 and 48h incubatio n. The mean dose-response curves for apoptosis of six healthy voluntee rs obtained with both methods were steep below 1Gy and flatter at high er doses. A slightly higher number of apoptotic cells was observed wit h DiOC(6), compared to Annexin V. This can be assigned to a minor DiOC (6)-int/PI- population. Forty-eight hour cultures contained higher num bers of apoptotic cells compared with 24h cultures. For both culture t imes, DiOC(6) and Annexin V detected a statistically significant diffe rence between a control sample and a 0.1 Gy irradiated one, illustrati ng the high sensitivity of the methods.