Abstract
Low dose radiation is reported to have beneficial effects such as attenuation of diabetes, autoimmune diseases, and cancer, which is called radiation hormesis. Because the disorder of accommodation in immune system is involved in such diseases, immunological network is assumed one of the targets for radiation hormesis. We have shown that continuous irradiation with low dose-rate gamma-ray enhances cellular immunity. Because hyper-activation of humoral immunity is involved in autoimmune diseases such as rheumatoid arthritis, it is expected that enhancement of cellular immunity by low dose-rate irradiation results in suppression of enhanced humoral immunity and amelioration of these autoimmune diseases. Here, we evaluated efficacy of continuous irradiation with low dose-rate gamma-ray on mouse experimental model for collagen-induced arthritis. Joint inflammation of mice immunized with 0.05 mg collagen in Freund's complete adjuvant, was detected 7 days after the immunization. Maximum inflammation was observed 40-50 days after the immunization, and gradually reduced thereafter. Continuous irradiation with 0.01-1 mGy/h gamma-ray significantly retarded and reduced the inflammation. The irradiation reduced serum IgM and IgG specific for mouse collagen, and recovered ability of splenocytes to produce interferon-gamma, which was suppressed by the immunization. Our results suggest that continuous irradiation with low dose-rate gamma ray is effective on collagen-induced arthritis at least in part through the enhancement of cellular immunity.
