Bronchial mucosal dendritic cells in smokers and ex-smokers with COPD: an electron microscopic study.

BACKGROUND: Bronchial mucosal dendritic cells (DCs) initiate and regulate immune responses to inhaled antigens, viruses and bacteria. Currently, little is known of their numbers in patients with chronic obstructive pulmonary disease (COPD). While reductions in their numbers have been reported recently in smokers with asthma, nothing is known of the effects of cigarette smoking on bronchial DCs in COPD. The present study compares DC numbers in smokers and ex-smokers with COPD. METHODS: Endobronchial biopsies were obtained from 15 patients with moderate to severe COPD (10 current smokers with median forced expiratory volume in 1 s (FEV1) 45.5% predicted (range 23-68) and 5 ex-smokers with median FEV1 30% predicted (range 21-52)), 11 non-smokers with asthma (median FEV1 102% predicted (range 89-116)) and 11 non-smoker healthy controls (median FEV1 110% predicted (range 92-135)). Transmission electron microscopy (TEM) was used to identify the total population of DCs by their ultrastructure and their number in the epithelium and subepithelium was counted. RESULTS: Median (range) DC numbers were significantly lower in current smokers with COPD in the epithelium (0.0 (0.0-156.8) cells/mm2) and the subepithelium (4.5 (0.0-63.6) cells/mm2) compared with ex-smokers with COPD (97.9 (93.5-170.3) cells/mm2 in the epithelium (p<0.05); 91.8 (38.2-283.3) cells/mm2 in the subepithelium (p<0.01)). DC numbers in ex-smokers with COPD were similar to those in subjects with atopic asthma and healthy controls (131.6 (33.3-235.5) cells/mm2 in the epithelium and 64.4 (0.0-182.4) cells/mm2 in the subepithelium for the latter). CONCLUSIONS: In COPD, bronchial mucosal DC numbers are lower in current smokers while, in those who quit, numbers are similar to non-smoking subjects with asthma and non-smoking healthy controls. The functional consequences of the reduction in mucosal DC numbers in smokers with COPD have yet to be determined.

Cytokine-induced airway epithelial ICAM-1 upregulation: quantification by high-resolution scanning and transmission electron microscopy.

The aim of this study was to investigate the variation of intercellular adhesion molecule (ICAM)-1 which occurs between individual airway epithelial cells of distinct phenotype. 16HBE14o- (16HBE) and BEAS-2B cell lines and human airway explants were cultured with medium alone or a mixture of tumour necrosis factor (TNF)-alpha (10 ng x mL(-1)) and interferon (IFN)-gamma (40 ng x mL(-1)) before being immunogold-labelled and examined quantitatively using sensitive high-resolution electron microscopic techniques. By enzyme-linked immunosorbent assay there was a 1.6-fold increase of ICAM-1 in the BEAS-2B cells following the cytokine mix which was not apparent in the 16HBE cells. However, high-resolution scanning electron microscopy demonstrated that an upregulation had occurred; median and ranges for gold particle number per 10 microm2 cell surface were: 7.9 (0-40) for nonstimulated and 19.1 (0-60 for stimulated) (p<0.01, Mann-Whitney U-test). The value for the nonstimulated BEAS-2B cells was 24.2 (0-60), 3-times higher that the constitutive expression in the 16HBE cells (p<0.01), whereas following stimulation, it was 68.5 (20-130) (p<0.01). Values for explant epithelial outgrowths were similar to the 16HBE cells. Immunohistochemistry of the explanted mucosa showed both constitutive and upregulated expression of epithelial ICAM-1 associated with basal and indeterminate cells rather than with ciliated or goblet cells. These results using high-resolution techniques indicate that there is marked cell-to-cell variation in cellular adhesion molecule expression and that it is the basal cells and less well differentiated (indeterminate) epithelial cells which are likely to play key roles in leukocyte retention via intercellular adhesion molecule-1.

Myofibroblast involvement in the allergen-induced late response in mild atopic asthma.

We undertook a detailed cellular and ultrastructural examination of bronchial biopsies from seven allergic asthmatic patients and 10 nonasthmatic control subjects (five atopic and five nonatopic) to determine the nature of the inflammation that occurs during allergen-induced late-phase responses (LPRs). The asthmatic subjects had mild asthma (FEV1 = 94 +/- 9% predicted; mean +/- SEM) and required only intermittent use of beta 2-agonists. Airway mucosal biopsy specimens were obtained on a single occasion from the nonasthmatic controls and on two occasions from the asthmatic subjects, at 24 h after diluent challenge and 24 h after challenge with allergen 3 wk later. The mean maximal decrease in FEV1 during the late response after allergen challenge was 30%, and that after administration of diluent was 4%. In coded plastic sections, subepithelial cells were counted with both light and electron microscopy, and the numbers present were expressed per 0.1 mm2 of tissue. Light microscopy revealed statistically significant increases in the total number of inflammatory cells (P < 0.02) and in "activated fibroblasts" after allergen challenge (P < 0.05). Electron microscopy showed significant increases after allergen challenge in the total number of eosinophils (P < 0.05) and cells with the ultrastructural features of myofibroblasts. The latter cells constituted 1.5% of cells after administration of diluent, and this increased to 15.5% after allergen challenge (P < 0.05). Mast cells were significantly more abundant in the atopic nonasthmatic controls than in the asthmatic subjects after allergen challenge. The study demonstrates that the profile of inflammatory cells in asthma at 24 h after allergen challenge is distinct from that in stable asthma and in nonasthmatic controls, and that migratory cells with a contractile phenotype appear in greater numbers in the late response. We propose that subjects who repeatedly develop a late response have increased numbers of migrating, contractile cells that may contribute to formation of the increased bronchial smooth-muscle mass observed in fatal asthma.

Airway and lung elastic fibre is not reduced in asthma nor in asthmatics following corticosteroid treatment.

By morphometric investigation of the relative content of elastic and collagen fibres, we have tested the hypothesis that loss of elastic fibres in the conducting airways and lung parenchyma may reduce tissue elastic recoil, resulting in increased airway maximal closure and apparent increased responsiveness. The study groups comprised: Group A (n = 11) with relatively mild atopic asthma using inhaled bronchodilators prn (i.e. short-term corticosteroids users); Group B (n = 9) with more severe asthma requiring inhaled bronchodilators regularly, and daily inhaled glucocorticosteroids (i.e. longterm corticosteroid users); Group C (n = 12) normal healthy workers. Bronchial biopsy samples were taken from three sites from the left lung. Group A biopsy samples were taken before and after a 4 wk treatment period with inhaled corticosteroids (200 micrograms b.i.d.) and the relative elastic and collagen fibre content of a subepithelial zone was determined from electron micrographs. In a parallel study, the relative proportion of elastic fibre in post mortem lung tissue samples (inner aspect of the bronchial wall, alveolar wall, and points of attachment of surrounding alveoli to intrapulmonary bronchi) from subjects suffering a fatal asthma attack (n = 11), and non-asthmatic suffering sudden death (n = 9), were determined using Miller's elastic and eosin counterstain for light microscopy. In bronchial biopsies of normal subjects, 4.6 (SEM 1.1)% of subepithelial connective tissue was elastic fibre, similar to mild asthmatic subjects, 1.9 (SEM 0.48)%. Neither short-term (4 weeks) inhaled corticosteroid (200 micrograms b.i.d.) nor long-term (< 6 months) treatment with variable doses of inhaled steroids (100-1000 micrograms b.i.d.) significantly altered the elastic or collagen content of the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of serous-like cells in the surface epithelium of human bronchioles.

The conductive airways of the mammalian lung are lined by several morphologically distinct cell types, both ciliated and non-ciliated. Of the non-ciliated secretory cells, mucous (goblet), Clara and neuroendocrine cells have been identified in adult human bronchiolar epithelium but, thus far, the serous cell has not. We have examined human membranous and respiratory bronchioles from macroscopically normal peripheral lung (n = 5 cases). For ultrastructural studies, a minimum of five nucleated, non-ciliated cell profiles, containing electron-dense secretory granules, were selected at random from both bronchiolar levels in each case, such that a total of 60 cells was examined. Data from the computer-aided image analysis of the cells indicated that two populations existed, differing in both granule area and granule number per cell p < 0.0005 by discriminant analysis. By visual inspection, the cells fell neatly into two groups: those which, were predominantly serous-like in type, and those which were "Clara". In the membranous bronchioles, serous-like cells had a mean(SEM) granule area per cell of 3.67(0.62) microns 2 and Clara cells 0.47(0.07) microns 2 (p < 0.001). Also, in the membranous bronchiole, the mean(SEM) number of granules in serous-like cells was 40(4.7) and in Clara cells 10(1.1) (p < 0.001). At the respiratory bronchiolar level, the corresponding means were similar to those of the membranous bronchioles and, likewise, serous and Clara cells were significantly different. Thus, our data, indicate that serous cells are present in the adult human bronchiole.