The enhancement of Th1 immunity and the suppression of tumour growth by low-dose γ-radiation
by Hisatake Hayase, Yasuhiro Ohshima, Mareyuki Takahashi, Shuji Kojima
International Journal of Low Radiation (IJLR), Vol. 5, No. 4, 2008

Abstract: To address if the modulation of immunity balance by low dose radiation is involved in the enhancement of the anti-tumour function, we examined the effect of 0.5 Gy γ-irradiation on the Th1/Th2 immunity balance in Ehrlich Solid Tumour (EST)-bearing mice. Repeated 0.5 Gy γ-irradiation significantly delayed the growth of tumours. The cytotoxic activities of Natural Killer (NK) cells and Cytotoxic T Lymphocytes (CTLs) were enhanced after repeated irradiation. Irradiation at 0.5 Gy significantly increased the Interferon (IFN)-γ production by splenocytes of tumour-bearing mice with their Interleukin (IL)-4 unchanged, resulting in the increased ratio of IFN-γ/IL-4, a hallmark of Th1 shift. Irradiation also increased the IL-12 production and cellular-reduced Glutathione (GSH) level of macrophages. The increase in the GSH level was found to be sustained for a few days after irradiation. These results indicate that low dose radiation shifts the immunity balance towards Th1 and consequently enhances the anti-tumour activity. The elevation of the GSH of macrophages by irradiation is suggested to be involved in the shift of the immunity balance.

Online publication date: Wed, 29-Oct-2008

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