Characterizing of gammaH2AX response of human lymphocytes to ionizing radiation

This work used flow cytometry to examine the feasibility of gammaH2AX as a marker for biological dosimetry and investigated the behavior of the H2AX historic for estimating the relative biological effectiveness of neutron irradiation. The work studied the dose rate effect for high and low dose rates. The behavior of different populations of human lymphocytes was investigated to determine whether one population has a more appropriate response for biological dosimetry.; The data showed that although the gammaH2AX biomarker has a linear dose response relationship, the usefulness of the biomarker is hampered with its short lifetime. Also, for the low dose rate irradiation, the plateau of the dose response curve makes it difficult to estimate dose. It was also shown that for human lymphocytes there is a clear dose rate effect for the gammaH2AX endpoint, with more damage measured when cells were irradiated at high dose rate than irradiated at low dose rate. The measurement of RBE using the gammaH2AX response gives unity; supporting a notion that the number of double strand breaks endpoint is mostly independent from linear energy transfer.