Natural killer cell activity in asbestos workers. Interactive effects of smoking and asbestos exposure

Both the numbers and function of natural killer (NK) cells in 60 were evaluated in asbestos cement workers grouped by smoking history and chest roentgenogram findings (ILO profusion scores less than 1/0 or greater than or equal to 1/0, or isolated pleural plaques). Worker and control subjects who smoked had smoking histories of less than 27 pack-years, a level of smoking lower than that previously determined to adversely affect NK function. Asbestos workers who did not smoke had percentages and total numbers of NK cells and NK function not different from that of nonsmoker control subjects. Workers who smoked and had evidence of asbestosis (ILO profusion category greater than or equal to 1/0) had significantly lower total numbers of NK cells and mononuclear cell NK activity than did smoker control subjects or smokers with pleural plaques only (p less than or equal to 0.05). Numbers of NK cells and NK cell function were not decreased in either of the asbestos-exposed smoking groups without asbestosis when compared to nonsmoker controls. We conclude that smoking and asbestos exposure interact to decrease mononuclear cell NK function in workers with levels of asbestos exposure sufficient to induce asbestosis. This finding may explain in part the previously reported synergistic effect of smoking and asbestos exposure on the risk of lung cancer. Furthermore, the data presented here clarify previous conflicting reports on NK function where asbestos exposed groups have not been stratified for analysis of data.