KL-6 expression and localization in diseased lung. (A) KL-6 expression and localization in representative sections of lung specimens from non-smoker, smoker, and patient with COPD. Positive KL-6 expression was seen mainly in type II pneumocytes as well as in macrophages in the lungs of non-smokers, smokers, and patients with COPD. The bronchial/alveolar epithelium of patients with COPD displayed highly positive areas of KL-6 staining in contrast to the situation in non-smokers and smokers. (B) Quantitative image analysis of KL-6 in the lung tissues of 7 non-smokers, 7 smokers and 14 patients with COPD. Three representative areas consisting of the parenchymal portion of the lung tissue were analyzed from all stained sections (sum of the bronchiolar/alveolar epithelium, interstitium and macrophages; Epi+Int+Mac). Quantitative image analysis of the immunoreactivity for KL-6 was also conducted separately in the bronchial/alveolar epithelium and interstitium (sum of the bronchiolar/alveolar epithelium and interstitium; Epi+Int; C) or the bronchial/alveolar epithelium (sum of the bronchiolar/alveolar epithelium; Epi; D). Data are presented as mean ± SEM. *p < 0.05; **p < 0.01; ***p < 0.001 (between all four groups, Kruskall-Wallis test). For patient characteristics see Table 3.