Inhibition of natural killer cell activity by alveolar macrophages in smokers

Abstract

We investigated the mechanism of the suppressive effect of alveolar macrophages on the activity of natural killer (NK) cells taken from bronchoalveolar lavage fluid and blood from smokers and non-smokers. The activity of NK cells was very low initially in both non-smokers and smokers. After 24 h in culture, the activity increased significantly in non-smokers but not smokers, and the activity of NK cells in the lung was significantly augmented by addition of interleukin-2, also only in non-smokers. Addition of alveolar macrophages from smokers had a significantly greater inhibitory effect on NK cell activity in blood than those from non-smokers. Indomethacin, catalase and thoiurea did not prevent the suppression of NK cell activity by alveolar macrophages, but superoxide dismutase prevented the inhibition. These results suggest that NK cell activity is suppressed in smokers by the release of oxygen radicals from alveolar macrophages.