Title: Activation of host-defense mechanism induced by exposure to a low dose of radiation: an approach to accumulate evidence on the interaction between the whole body and radiation

Authors: Junko Matsubara, Morio Yonezawa

Addresses: Yokohama City University School of Medicine, Yokohama 236-0004 and Nuclear Safety Commission, Cabinet Office, Chiyodaku, Tokyo 100-8970, Japan. ' Research Institute for Advanced Sciences and Technology, Osaka Prefecture University, Sakaishi, Osaka 599-8570, Japan

Abstract: We found that the effect of a small dose of irradiation on the whole body exists at certain dose level windows which induce delayed radio-protective effects on an animal after a fixed time span depending on its dose levels. The striking increase of survivals against the second mid-lethal irradiation was observed in mice pre-irradiated with 5 cGy eight weeks before, or pre-irradiated with 50 cGy two weeks before. Thymocyte apoptosis was increased six hours after 5 or 50 cGy pre-irradiation. While in spleen plaqueforming cell counts with SRBC immunisation increased at the very time when mice manifested the optimal increase in survival, namely two weeks after 50 cGy pre-irradiation or eight weeks after 5 cGy pre-irradiation. Stress inducing treatment (e.g. administration of a heavy metal salt or irradiation at higher dose etc.) seems to act within a few days stimulating more events at the biochemical level. However, the low-dose irradiation seems to act more at the immune level influencing the cooperation between immune system components in the whole body.

Keywords: pre-irradiation; low-dose; mice; survival; apoptosis; plaque-forming cell counts; activation of immune function (PFC).

DOI: 10.1504/IJLR.2004.003869

International Journal of Low Radiation, 2004 Vol.1 No.2, pp.180 - 188

Published online: 10 May 2004 *

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