Dose response and repair kinetics of γ-H2AX foci induced by in vitro irradiation of whole blood and T-lymphocytes with X- and γ-radiation

Abstract

Purpose: Dose response and repair kinetics of phosphorylated histone H2A isoform X (γ-H2AX) foci in T-lymphocytes were investigated in the low-dose range after in vitro irradiation of whole blood and T-lymphocytes with 100 kVp X-rays and 60Co γ-rays.Materials and methods: Whole blood or isolated T-lymphocytes were irradiated in vitro and γ-H2AX foci were scored. Dose response was determined in the 0–500 mGy dose range. Foci kinetics were studied at doses of 5 and 200 mGy up to 24 h post-irradiation.Results: After X-irradiation, the dose response for whole blood shows a biphasic behaviour with a low-dose hypersensitivity, which is less pronounced for isolated T-lymphocytes. In contrast, γ-radiation shows a linear dose response for both irradiation conditions. Concerning repair kinetics, delayed repair was found after X-ray whole blood irradiation (5 and 200 mGy) with 40% of the foci persisting 24 h post-irradiation. This number of foci is reduced to 10% after irradiation of isolated T-lymphocytes with 200 mGy X-rays. On the contrary, γ-H2AX foci are reduced to background levels 24 h post-irradiation with 200 mGy 60Co γ-rays.Conclusion: γ-H2AX foci response and repair kinetics depend on irradiation conditions and radiation quality, possibly linked to Bystander response.