Effects of adaptive response induced by low-dose ionizing radiation on immune system in spleen lymphocytes of BALB/C mice.

Radioadaptive response (RAR) describes the phenomenan where low dose (called the 'priming dose') of ionizing radiation (IR) reduces harmful effects of subsequent higherdoses of IR (called the 'challenge dose'). The aim of this study was to investigate the role of immune system genes in the adaptive response induced by low-dose of ionizing radiation. Mice were exposed to γ -rays from a ⁶⁰Co source, to a series of priming and challenge doses at 31 mGy/min and 449 mGy/min respectively. Challenge dose was delivered 24 h following to priming dose. Expression level of two genes; IFN- γ IL-4 were examined by relative quantitative real-time polymerase chain reaction (RT-PCR) in 24 h after exposure. The non-parametric two independent samples T-test were performed to compare mean of gene expression level. The results of this study showed that the gene expression of both IL-4 and IFN- γ values significantly reduced after receiving high doses (P < 0.0001) whereas IL-4 gene expression level increased after low dose. Interestingly, there was no significant difference between IL-4 and IFN- γ genes expression of the adaptive and control group. Gene expression of TGF- β after low and high dose and adaptive group significantly reduced (P < 0.001). The ratio of IFN- γ /IL-4 for high dose group was increased significantly (P < 0.0001). These results are evident for that ionizing radiation may play a role in Th1 and Th2 cytokine expression immune response shift of Th1 cells toward Th2 after low and high dose radiation. Adaptive response to ionizing radiation induced by low dose of gamma ray can reduce the harmful effect of the radiation. There is not any relationship that might lead to a conflict of interest. Mashhad University of Medical Sciences (MUMS) has financially supported this work. [ABSTRACT FROM AUTHOR]