Analysis of immune cell populations and cytokine profiles in murine splenocytes exposed to whole-body low-dose irradiation

Abstract

Purpose: In contrast to high-dose therapeutic irradiation, definitive research detailing the physiological effects of low-dose irradiation is limited. Notably, the immunological response elicited after low-dose irradiation remains controversial.

Materials and methods: Female C57BL/6 mice were whole- body-irradiated with a single or three daily fractions up to a total dose of 0.1, 1, or 10 cGy. Blood and spleen were harvested 2, 7 and 14 days after irradiation.

Results: The splenic CD4⁺ T cell subpopulations were temporarily increased at 2 days after single or fractionated irradiation, whereas the percentage of dendritic cells (DC) and macrophages was decreased. Whereas CD8⁺ T cell populations were decreased in single-dose irradiated mice at day 7, early and sustained reduction of CD8⁺ T cell numbers was observed in fractionated- dose-irradiated mice from day 2 until day 14. In addition, single-dose irradiation resulted in a Th1 cytokine expression profile, whereas fractionated-dose irradiation drove a Th2 shift. Additionally, increased expression of immune-related factors was observed at early time-points with single-dose irradiation, in contrast to the dose-independent induction following fractionated-dose irradiation.

Conclusions: Our results demonstrate that low-dose irradiation modulates the immune response in mice, where the sensitivity and kinetics of the induced response vary according to the dosing method.

Keywords::

• Low-dose irradiation
• whole-body irradiation
• immune response
• cytokine expression
• reactive oxygen species

Acknowledgements

This work was supported by the Nuclear Research & Development Program (NRF-2013M2A2A7028423) of the National Research Foundation of Korea and by Grant No. 20131610101840 from the Ministry of Trade, Industry & Energy. This study was also partially supported by a grant of the RTR 50457-2014, Korea Institute of Radiological & Medical Sciences.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.