Subpopulations of alveolar macrophages in smokers and nonsmokers: relation to the expression of CD11/CD18 molecules and superoxide anion production.

We were previously able to show that the number of alveolar macrophages (AM) expressing CD11/CD18 molecules is increased in smokers compared with nonsmokers and related to the superoxide anion (O2-) production of these cells. Since it has been demonstrated that AM are a heterogeneous cell population that can be separated by density, we performed this study to investigate the expression of CD11/CD18 molecules and O2- production in relation to cell density of AM from smokers and nonsmokers. AM were obtained by bronchoalveolar lavage (BAL) from smokers (n = 32) and nonsmokers (n = 20). Subpopulations were isolated using discontinuous Percoll density-gradient centrifugation with four densities (fraction 1: 1.030; fraction 2: 1.040; fraction 3: 1.050; and fraction 4: 1.070 g/ml). Expression of CD11/CD18 on freshly isolated cells and on AM before and after density centrifugation was studied using peroxidase-antiperoxidase staining. The contribution of AM subpopulations to O2- production in smokers was determined by monitoring the reduction of ferricytochrome C to ferrocytochrome C. We obtained 0.92 +/- 0.1 x 10(5) AM/ml BAL in nonsmokers and 2.4 +/- 0.3 x 10(5) AM/ml in smokers. Recovery after density centrifugation was > or = 72%. The absolute number of AM in smokers was significantly increased in fractions 3 and 4 (median 4.37 x 10(6) and 2.05 x 10(6), respectively) compared with nonsmokers (median 1.26 x 10(6) and 0.7 x 10(6), respectively) (p < 0.05). In both smokers and nonsmokers, fractions 3 and 4 showed a comparable increase in the percentage of CD11/CD18-positive AM compared with fractions 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)