GST pi and mu immunoreactivities in human lung. A. In Western analysis of GST pi in lung homogenates, the level of GST pi was elevated in Stage I-II COPD compared to that in healthy smokers (p = 0.002). B. In immunohistochemical staining, GST pi was mainly expressed in the epithelium of airways and alveoli. C. Western analysis of the lung homogenates for GST mu showed some variability but the difference between the groups was not significant (p = 0.063). C. In immunohistochemical staining, GST mu was located in the macrophages; the expression in bronchial and alveolar epithelium was weak.