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

Abstract

Purpose: To assess the use of phosphorylated histone H2AX protein (γ-H2AX) in human blood leukocytes as a rapid screening tool for radiation biodosimetry using a method that examines the characteristics of γ-H2AX phosphorylation in a variety of lymphocyte subsets following exposure to radiation.

Materials and methods: Human peripheral blood exposed to 0–10 Gy of ¹³⁷Cs irradiation and cultured for 0–48 h was analysed using a rapid whole blood flow cytometry assay to measure γ-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 γ-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.

Keywords:

• γ-H2AX
• human lymphocytes
• radiation
• flow cytometry