[Immunohistochemical study of myofibroblast and S-100 protein positive cells in interstitial pneumonia associated with collagen vascular disease].

Immunohistochemical study was carried out in patients with collagen vascular disease associated with interstitial pneumonia. The subjects were 16 patients, consisting of seven rheumatoid arthritis (RA), five dermatomyositis (DM) and four progressive systemic sclerosis (PSS), in whom the pathological findings were consistent with usual interstitial pneumonia. Immunohistochemical examinations were performed by the ABC method using antibodies to vimentin (vim), alpha-smooth muscle actin (alpha-SMA), and S-100 protein. In fibrosis associated with RA, proliferation of alpha-SMA-positive myofibroblasts was widely observed in all subjects. Myofibroblasts were present also in patients with DM and PSS, but not as notable as in those with RA. Proliferation of vim-positive fibroblasts was observed in patients with idiopathic pulmonary fibrosis (IPF). Diverse S-100 protein positive cells appeared in patients with acute exacerbations of RA, especially when associated with bronchiolitis obliterans organizing pneumonia (BOOP) pattern. S-100 protein positive cells were observed occasionally also in patients with DM and PSS, but they markedly decreased in number, compared to those with RA. They were generally hard to detect in lungs of patients with IPF. These findings suggest that interstitial pneumonia associated with collagen vascular disease can be fairly clearly differentiated from IPF each other, based on the degree of proliferation of myofibroblasts and on the presence of S-100 protein positive cells in number.