Suppression of Thymic Lymphoma Induction by Life-Long Low-Dose-Rate Irradiation Accompanied by Immune Activation in C57BL/6 Mice

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 ...