Inhibition of lung natural killer cell activity by smoking: The role of alveolar macrophages

Background: It is known that natural killer (NK) cell activity in the lung of smokers (SM) is lower than in non-smokers (NS). However, little is known about the underlying mechanisms. Objective: The purpose of this work was t o investigate the mechanisms of the inhibition of NK cell activity by alveo lar macrophages (AM) in SM. Methods: Lung effector cells and AM were obtain ed using bronchoalveolar ravage. The NK cell activity was assayed by Cr-51 release method after incubation of 4 and 24 h, using K562 as target cell. A M were added at a concentration of 25% to effector cells. Results: Followin g 24-hour culture, NK cell activity significantly increased in the NS but n ot in the SM, Lung NK cell activity was significantly augmented by interleu kin-2 in the NS but not in the SM. Addition of AM to the NK cell preparatio n from SM exerted a significantly greater suppressive effect on autologous blood NK cell activity than in the NS. Indomethacin, catalase or thiourea d id not prevent AM-mediated suppression of NK cell activity, in contrast to superoxide dismutase. Conclusions: These results suggest that the suppressi on of NK cell activity by AM in SM may be caused by O-2(-) release rather t han by prostaglandins, H2O2 or OH release from AM. Copyright (C) 2001 S. Ka rger AG, Basel.