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 h uman peripheral blood lymphocytes using an alkaline comet assay. The isolat ed cells were incubated with an autologous plasma for 1 h at 37 degreesC be fore performing the assay. The cells exhibited a significant increase in th e tailmoment when the irradiated blood (2 Gy, 570 keV neutron) was the sour ce of plasma. The genotoxic effect lasted for 96 h when stored at -20 degre esC. It is believed to be mediated by the release of cytokines or other fac tors released by the irradiated cells. Plasma obtained from unirradiated bl ood or further irradiation of plasma did not enhance the tailmoment signifi cantly. Thus, the adverse effect of neutron-exposure can be passed on to un irradiated neighbourhood through irradiated blood tissue without involving cell-cell contact. The non-targeted radiation effect assumes greater conseq uences in radiotherapy and biodosimetry.