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1 February 2005 Suppression of Thymic Lymphoma Induction by Life-Long Low-Dose-Rate Irradiation Accompanied by Immune Activation in C57BL/6 Mice
Yasuhiro Ina, Hiroshi Tanooka, Takeshi Yamada, Kazuo Sakai
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Abstract

Ina, Y., Tanooka, H., Yamada, T. and Sakai, K. Suppression of Thymic Lymphoma Induction by Life-Long Low-Dose-Rate Irradiation Accompanied by Immune Activation in C57BL/6 Mice. Radiat. Res. 163, 153–158 (2005).

The induction of thymic lymphomas by whole-body X irradiation with four doses of 1.8 Gy (total dose: 7.2 Gy) in C57BL/6 mice was suppressed from a high frequency (90%) to 63% by preirradiation with 0.075 Gy X rays given 6 h before each 1.8-Gy irradiation. This level was further suppressed to 43% by continuous whole-body irradiation with 137Cs γ rays at a low dose rate of 1.2 mGy/h for 450 days, starting 35 days before the challenging irradiation. Continuous irradiation at 1.2 mGy/h resulting in a total dose of 7.2 Gy over 258 days yielded no thymic lymphomas, indicating that this low-dose-rate radiation does not induce these tumors. Further continuous irradiation up to 450 days (total dose: 12.6 Gy) produced no tumors. Continuously irradiated mice showed no loss of hair and a greater body weight than unirradiated controls. Immune activities of the mice, as measured by the numbers of CD4 T cells, CD40 B cells, and antibody-producing cells in the spleen after immunization with sheep red blood cells, were significantly increased by continuous 1.2-mGy/h irradiation alone. These results indicate the presence of an adaptive response in tumor induction, the involvement of radiation-induced immune activation in tumor suppression, and a large dose and dose-rate effectiveness factor (DDREF) for tumor induction with extremely low-dose-rate radiation.

Yasuhiro Ina, Hiroshi Tanooka, Takeshi Yamada, and Kazuo Sakai "Suppression of Thymic Lymphoma Induction by Life-Long Low-Dose-Rate Irradiation Accompanied by Immune Activation in C57BL/6 Mice," Radiation Research 163(2), 153-158, (1 February 2005). https://doi.org/10.1667/RR3289
Received: 30 January 2004; Accepted: 1 September 2004; Published: 1 February 2005
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