Bronchoalveolar lavage fluid obtained from smokers exhibits increased monocyte chemokinetic activity

Alveolar macrophages, which are cells derived from blood monocytes, accumulate within the lower respiratory tract of cigarette smokers. One mechanism to account for this accumulation of alveolar macrophages may be an increase in the migration of blood monocytes into the lungs of smokers. To evaluate this hypothesis, bronchoalveolar lavage fluid (BALF) was obtained from 15 smokers and 16 nonsmokers. The smokers' BALF possessed a significantly increased capacity to attract normal blood monocytes when evaluated using a blind-well chamber technique (26.2 ± 7.6 vs. 14.8 ± 6.9 cells/high-power field, P < 0.01). Checkerboard analysis of the activity revealed that it was predominantly chemokinetic. Partial characterization of the activity in smokers' BALF revealed that it was lipid soluble but only partially sensitive to trypsin and heat. The chemokinetic activity correlated with alveolar macrophage numbers in the BALF (r = 0.4391, P = 0.009). Furthermore, both the chemokinetic activity and alveolar macrophage number correlated with alterations of respiratory function (forced expiratory volume in 1 s, diffusing capacity for carbon monoxide, and forced expiratory flow at 75% of the vital capacity). These results suggest that the increase in alveolar macrophage number present in the BALF of cigarette smokers may be due, at least in part, to an increased amount of chemokinetic factor(s) in the smokers' BALF, and these factor(s) may participate in the decline of respiratory function associated with cigarette smoking, probably by recruiting monocytes into lung.