Different inflammatory cell pattern and macrophage phenotype in chronic obstructive pulmonary disease patients, smokers and non-smokers

Abstract

Smokers exhibit airway inflammation and increased number of alveolar macrophages (AM), but not all develop chronic obstructive pulmonary disease (COPD). We hypothesized that AMs in COPD patients have an altered functional capacity mirrored in a different phenotype. Sixteen steroid-naive COPD patients [forced expiratory volume in 1 s (FEV(1)) < 70% of predicted] underwent bronchoalveolar lavage (BAL). Age- and smoking-matched non-obstructive smokers (n = 10) and healthy non-smokers (n = 9) served as controls. Nine COPD patients had a BAL cell yield sufficient for flow cytometry analysis, where expression of AM cell surface markers reflecting various functions was determined. AMs from COPD patients showed decreased expression of CD86 (co-stimulation) and CD11a (adhesion) compared to smokers' AMs (P < 0.05). Furthermore, smokers' AMs showed lower (P < 0.05) expression of CD11a compared to non-smokers. AM expression of CD11c was higher in the COPD and smokers groups compared to non-smokers (P < 0.05). The expression of CD54 (adhesion) was lower in smokers' AMs compared to non-smokers (P < 0.05), whereas CD16 was lower (P < 0.05) in COPD patients compared to non-smokers. The AM expression of CD11b, CD14, CD58, CD71, CD80 and human leucocyte antigen (HLA) Class II did not differ between the three groups. The AM phenotype is altered in COPD and further research may develop disease markers. The lower AM expression of CD86 and CD11a in COPD implies a reduced antigen-presenting function. Some alterations were found in smokers compared to non-smokers, thus indicating that changes in AM phenotype may be associated with smoking per se. The functional relevance of our findings remains to be elucidated.

Fig 1

Flow cytometry analysis of alveolar macrophage autofluorescence. Autofluorescence of alveolar macrophages, before quenching, is given as mean fluorescence intensity (MFI) for the three groups: chronic obstructive pulmonary disease (COPD), ‘healthy’ smokers (HS) and non-smokers (NS). Each point depicts the result from one subject and the median of the group is marked with a horizontal bar. Significant difference between groups is shown as ***P < 0·001. Statistical analysis was performed using Kruskal–Wallis and Nemenyi tests.

Fig 2

Flow cytometry analysis of cell surface molecules of alveolar macrophages. A short description of surface molecules is given in Table 2. Results are presented as mean fluorescence intensity (MFI) for the three groups: chronic obstructive pulmonary disease (COPD), ‘healthy’ smokers (HS) and non-smokers (NS). Each point depicts the result from one subject and the median of the group is marked with a horizontal bar. Significant difference between groups is shown as *P < 0·05. Statistical analysis was performed using Kruskal–Wallis and Nemenyi tests.

Fig 2

Flow cytometry analysis of cell surface molecules of alveolar macrophages. A short description of surface molecules is given in Table 2. Results are presented as mean fluorescence intensity (MFI) for the three groups: chronic obstructive pulmonary disease (COPD), ‘healthy’ smokers (HS) and non-smokers (NS). Each point depicts the result from one subject and the median of the group is marked with a horizontal bar. Significant difference between groups is shown as *P < 0·05. Statistical analysis was performed using Kruskal–Wallis and Nemenyi tests.

Fig 3

The expression of CD86 in alveolar macrophages, presented as mean fluorescence intensity (MFI), correlates to the lung function assessed as forced expiratory volume in 1 s (FEV₁) (% of predicted) (P < 0·001, r = 0·73). The figure presents data from chronic obstructive pulmonary disease (COPD) patients and ‘healthy’ smokers, and each point depicts the result from one participant. Statistical calculation performed using Spearman' test.