Comet assay to assess the non-target effect of neutron-radiation in human peripheral blood.

The non-target effect of neutron-irradiation was assessed in unirradiated human peripheral blood lymphocytes using an alkaline comet assay. The isolated cells were incubated with an autologous plasma for 1 h at 37 degrees C before performing the assay. The cells exhibited a significant increase in the tailmoment when the irradiated blood (2 Gy, 570 keV neutron) was the source of plasma. The genotoxic effect lasted for 96 h when stored at -20 degrees C. It is believed to be mediated by the release of cytokines or other factors released by the irradiated cells. Plasma obtained from unirradiated blood or further irradiation of plasma did not enhance the tailmoment significantly. Thus, the adverse effect of neutron-exposure can be passed on to unirradiated neighbourhood through irradiated blood tissue without involving cell-cell contact. The non-targeted radiation effect assumes greater consequences in radiotherapy and biodosimetry.