The response of gamma -H2AX in human lymphocytes and lymphocytes subsets measured in whole blood cultures

PURPOSE: To assess the use of phosphorylated histone H2AX protein (gamma-H2AX) in human blood leukocytes as a rapid screening tool for radiation biodosimetry using a method that examines the characteristics of gamma-H2AX phosphorylation in a variety of lymphocyte subsets following exposure to radiation. MATERIALS AND METHODS: Human peripheral blood exposed to 0-10 Gy of (137)Cs irradiation and cultured for 0-48 h was analysed using a rapid whole blood flow cytometry assay to measure gamma-H2AX phosphorylation in different lymphocyte subpopulations. RESULTS: Lymphocyte subsets displayed a similar linear dose response relationship, although cluster of differentiation 4(+) (CD4(+)) and CD8(+) lymphocytes were found to express H2AX phosphorylation on the order of 1.5 times higher than CD19(+) lymphocytes. Phosphorylation of all lymphocyte subsets reached a maximum at 1.5 h and had essentially returned to baseline levels 24 h post-exposure. CONCLUSIONS: Differences in the expression level of gamma-H2AX between lymphocyte subsets were minimal. The usefulness of this assay for radiation biodosimetry is hampered by its relatively quick lifetime kinetics and large inter-individual variation. Therefore, it could only be useful if samples were obtained within 24 h of exposure. Even in this situation, the assay could only be used as an indicator of exposure and not a dosimeter.