Sci‐AM Fri ‐ 04: Radiation induced apoptosis and chromosomal aberrations in human lymphocytes: Estimating the risks associated with radiation exposures

Research conducted at McMaster University has shown a relative biological effect (RBE) of unity, between 280keV neutrons and gamma radiation, for the induction of apoptosis in human lymphocytes. Similar results have also been seen by Vral et al. (1998) and Warenius and Down (1995) for the induction of apoptosis in human lymphocytes and mouse thymocytes respectively. It has previously been reported that neutrons of energies 36keV to 14.6Mev have an RBE ranging from 67.1±28.9 to 16±6.8 for induction of dicentrics in human lymphocytes respectively (Schmid et al. , 2003, 2002, and 2000). This discrepancy between RBEs suggests that further work is needed to understand why human lymphocytes have such varying response to different radiations. Radiation‐induced apoptosis and chromosomal aberrations are being measured in parallel. In this study, it was found that 280keV neutron induce chromosome breaks with an RBE of 6.4 (for the induction of 1 break/cell). An experiment was established to study the types of chromosomal aberrations which exist in the lymphocytes which have not committed apoptosis 48 hours after radiation. Isolated lymphocytes were incubated for 48 hours in complete media before PHA stimulation. This allowed the analysis of the chromosomal damage present in cells that do not commit apoptosis immediately. It is possible that the cells which have not committed apoptosis at 48 hours are those which have been less severely damaged and may be viewed by the organism as being repairable.