The effect of low dose of radiation at the whole body level

The interaction between body and radiation is reviewed partly based on author's research experiences. Radiation induces generation of free radicals in the body, and which produces chemical protectants like cytokines against the radicals. Those protectants interestingly have radio-protective effects. The author classifies the radiation adaptive responses into cellular and whole body levels in discussing the effect of radiation on cells. Activation of immune system by certain stimuli is described on experiments in 75-500 mGy X-irradiated mice in relation to T-cell maturation. Epidemiological investigations for the low dose radiation effects and risk assessment of carcinogenicity are summarized in such cases as Hiroshima and Nagasaki, Chernobyl accident, radiation workers and people living in high-level natural radiation dose area. Studies focusing on the radiation effect on the whole body as well as on the molecular level from the wide viewpoint are expected. (K.H.)