Morphological studies of cultured human pulmonary macrophages

A morphological classification scheme is developed for the quantitative in vitro examination, by scanning electron microscopy (SEM), of pulmonary alveolar macrophages (AM) from human cigarette smokers and nonsmokers. The AM were obtained by bronchopulmonary lavage, allowed to attach to glass coverslips in a serum containing medium, cultured for 1, 2, or 25 hours, and examined in the SEM. Fifty cells per sample were randomly selected for detailed morphological analysis using a predetermined sampling grid. Area, form, degree of cell spreading, and the relative abundances of surface features, including ruffles, filopodia, blebs, microvilli, multiple features, and no surface features were quantified. Smoker AM had a greater incidence of ruffles, filopodia, multiple features, and rounded cells; nonsmoker AM had greater incidences of featureless and spread cells. Microvilli and blebs were observed infrequently and displayed no trends with respect to differences between smokers and nonsmokers. The incidence of filopodia, multiple features, and intermediate shapes generally increased with increasing culture time, and a decreasing incidence with increasing time in culture was observed for featureless and spread cells. For the 1- and 2-hour culture periods, slightly greater sizes, size variances, form factors, and form factor variances were observed for smoker AM; however, after 25 hours in culture, nonsmoker AM populations possessed these characteristics. Area frequency distributions appeared to be logarithmically normal in distribution. Statistical analyses indicated that for area and form, the greatest variance was due to variations among the individuals lavaged.