Photomicrographs of histopathological and immunohistochemical studies of representative surgical lung biopsy specimens (A-E; idiopathic UIP, F-J; CVD-associated UIP, K-O; idiopathic NSIP, scale bar = 100 μm). Histopathological examination (hematoxylin-eosin staining) revealed fibroblastic foci in both idiopathic UIP (A) and CVD-associated UIP (F), and fibroblast proliferation in idiopathic NSIP (K). Hyperplastic cuboidal epithelial cells were stained with cytokeratin, indicating that these cells were type II pneumocytes (B, G and L). Strong expression of HSP47 was noted predominantly in fibroblasts and type II pneumocytes in idiopathic UIP (C). Weak or no expression of HSP47 was noted in fibroblasts and type II pneumocytes in CVD-associated UIP (H). In idiopathic NSIP, strong expression of HSP47 was noted in fibroblasts, but not in type II pneumocytes (M). Type I procollagen was strongly expressed predominantly in fibroblasts and type II pneumocytes in idiopathic UIP (D), but neither in CVD-associated UIP (I) nor idiopathic NSIP (N). Expression of α-SMA was noted in some of fibroblasts, indicating that these cells were myofibroblasts, in all three diseases (E, J and O). Insets c, d, h, i, m and n are pictures taken at high power magnification (scale bar = 20 μm) of corresponding C, D, H, I, M and N sections to clearly show the phenotypic difference of type II pneumocytes. α-SMA = α-smooth muscle actin; CVD = collagen vascular disease; HSP47 = heat shock protein 47; NSIP = nonspecific interstitial pneumonia; UIP = usual interstitial pneumonia.