To study the nature of differentially manifested adaptive response of an organism according to the intensities of the stress, the immune effects of different levels of repeated hypoxia were investigated. Four experimental groups (NH : not -handled, 20% : handled, 15% or 10% : exposed to 15% or 10% O 2
O2
씨오투 with balanced nitrogen, respectively) of mice were exposed to different levels of hypoxia for 60 min/day, 5days/week in a repeated and intermittent manner. After 8 weeks' exposure to hypoxia environment, mice were subjected to immune function measurements, A decreased proportion of CD3+ CD8 phenotype cells in the study of splenocyte subsets was observed in the 10% group. Ovalbumin-stimulated IgG2a production was increased in the 15% group, while no changes were noted in the IgGl and IgM production. No significant changes of the antigen-stimulated splenocyte proliferation and the natural killer cell cytotoxicity were found. These results show that the stress effects on the immune systems can be varied according to the strength of the stress and that a mild level of repeated hypoxic stress can enhance the immune function of mice in this experimental model.