Flow cytometric analysis of lymphocyte surface markers following a 1-Gy dose of gamma radiation

Flow cytometric analysis of lymphocytes labeled with monoclonal antibodies was undertaken in order to compare the mean fluorescent intensity of several surface membrane antigens (markers) from irradiated and nonirradiated blood samples. Whole blood subjected to a 1-Gy (100-rad) dose of 1.25 MeV gamma radiation from a 60Co radioisotope source was compared with nonirradiated blood drawn simultaneously from the same healthy subject. Twenty runs were performed in which the following T and B lymphocyte and natural killer surface markers were analyzed: CD2, CD3, 13, CD4, CD29, CD45RA, CD8, CD56, and CD19. The data demonstrate a radiation-induced decrement in the mean fluorescent intensity of the high molecular weight markers CD45RA and CD56 (decrement is -3.3% and -7.2%, respectively). The statistical validity of these values was confirmed using paired t-tests, which yielded p values of p < 0.02 (CD45RA) and p < 0.01 (CD56). The fluorescent intensity is proportional to the number of intact binding sites on the lymphocyte surface and the observed decrement directly infers that damage to some sites occurred. These results illustrate a measurable effect on the lymphocyte membrane at a radiation dose at which many lymphocytes will survive, yet may be immunologically altered. This study may have important implications for personnel exposed to ionizing radiation, such as astronauts on long duration missions and radiation workers involved in accidental exposures.