Repeated Irradiations with γ-rays at a Dose of 0.5 Gy May Exacerbate Asthma

Abstract

We previously showed that 0.5 Gy whole-body γ-ray irradiation with a single or small number of repeated exposures inhibits tumor growth in mice, via elevation of the IFN-γ/IL-4 ratio concomitantly with a decrease in the percentage of B cells. Here we examined whether repeated 0.5 Gy γ-rays irradiation can improve asthma in an OVA-induced asthmatic mouse model. We found that repeated irradiation (10 times) with 0.5 Gy of γ-rays significantly increased total IgE in comparison with the disease-control group. The levels of IL-4 and IL-5 were also significantly higher in the γ-ray-irradiated group, while that of IFN-γ was significantly lower, resulting in a further decrease of the IFN-γ/IL-4 ratio from the normal value. These results indicate that the repeated irradiation with γ-rays may exacerbate asthma, and may have opposite effects on different immune reactions unlike the irradiation with a single or small number of repeated exposures.