Title: The enhancement of Th1 immunity and the suppression of tumour growth by low-dose γ-radiation

Authors: Hisatake Hayase, Yasuhiro Ohshima, Mareyuki Takahashi, Shuji Kojima

Addresses: Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda, Chiba 278–8510, Japan. ' Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda, Chiba 278–8510, Japan. ' Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda, Chiba 278–8510, Japan. ' Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda, Chiba 278–8510, Japan

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.

Keywords: low-dose radiation; Th1 immunity; immunity balance; tumour growth; cell-mediated immunity; NK cells; cytotoxic T lymphocytes; CTLs; glutathione; GSH; low radiation; gamma irradiation; mice; macrophage levels.

DOI: 10.1504/IJLR.2008.020977

International Journal of Low Radiation, 2008 Vol.5 No.4, pp.275 - 289

Available online: 29 Oct 2008 *

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