GST alpha expression in the airways and in total lung homogenates. A. The GST alpha immunoreactivity in airway epithelium of central and peripheral airways. The staining was graded as negative (0), weak (1) or moderate (2) or intense (3). The GST alpha immunoreactivity was strong in the epithelium of both large, cartilaginous airways as well as in the epithelium of small peripheral bronchioli. There was a trend for diminished immunoreactivity in cases of very severe (Stage IV) COPD but the difference between the groups was not statistically significant. The means are shown as columns with error bars representing SEM. B. The percentage of GST alpha positive epithelial cells was observed to decrease in the large airways of the patients with very severe (Stage IV) COPD compared to non-smokers (p = 0.02). C. Western analysis of GST alpha in the lung homogenates of healthy non-smokers and smokers and in patients with different stages of COPD showed an increased immunoreactivity in patients with Stage I-II COPD compared to non-smokers or smokers (p = 0.007). The means of the measured sum intensities are shown as columns with error bars representing SEM.