Natural killer activity is present in rat lung lavage and inhibited by lidocaine

Natural killer (NK) cells play an important role in defense against tumors and certain infected cells. Although NK activity is present in cells recovered from lung parenchyma, its demonstration in cells retrieved from normal bronchoalveolar lavage (lung lavage) has been difficult. In this study, we report that NK cells are present and active in normal rat lung lavage. Purified effector cells retrieved from lung lavage and peripheral blood mononuclear cells were compared for NK activity. NK activity was tested in a four hour 51-chromium release assay against radiolabeled Yac-1 target cells and expressed as lytic units (LU). There was no difference in NK activity between the blood and lung (80 +/- 10 LU vs. 62 +/- 15 LU). Since lidocaine is used in lung lavage for topical anaesthesia in humans and to increase the cell yield in animals, we also sought to determine if it could affect NK activity. We found that lidocaine inhibited NK activity in a dose dependent manner when it was instilled into the airways prior to performance of lavage. Lidocaine did not affect the yield of cells recovered from lavage, their relative proportions, nor their viability. Lung macrophages (93 +/- 1% nonspecific esterase positive) inhibited blood NK activity, an effect significantly augmented by lidocaine. In sum, we report that NK activity in lung lavage is similar to that found in blood and may be regulated by alveolar macrophages and that topical lidocaine inhibits NK activity, an effect which needs to be considered in studies of these cells from lung lavage.