Sequential changes of KL-6 in sera of patients with interstitial pneumonia associated with polymyositis/dermatomyositis

Objective—KL-6 is a mucin-like high molecular weight glycoprotein, which is strongly expressed on type II alveolar pneumocytes and bronchiolar epithelial cells. It has been demonstrated that the KL-6 antigen is a useful marker for estimating the activity of interstitial pneumonia. In this study, it is hypothesised that serum KL-6 is a useful marker to evaluate the activity of interstitial pneumonia associated with polymyositis/ dermatomyositis (PM/DM). Methods—KL-6 was measured in sera in 16 patients diagnosed with PM/DM. Five had non-specific interstitial pneumonia (NSIP), three had diVuse alveolar damage (DAD), and eight had no pulmonary involvement, and 10 were normal nonsmokers as a control group. The correlation was also evaluated between the KL-6 level and each clinical course in patients with pulmonary involvement associated with PM/DM. Immunohistochemical analysis using monoclonal anti-KL-6 antibody was also performed. Results—KL-6 concentrations in sera of patients with interstitial pneumonia associated with PM/DM were significantly high compared with those of PM/DM without interstitial pneumonia, and normal non-smokers. KL-6 concentrations in sera in patients with DAD significantly increased compared with those of other groups. KL-6 values in sera changed according to the progression or improvement of interstitial pneumonia. Immunohistochemical study using pulmonary tissues obtained from patients with DAD demonstrated that the hyaline membrane, proliferating type II pneumocytes, bronchial epithelial cells and some endothelial cells in pulmonary veins were stained by antihuman KL-6 antibody. Conclusion—These data demonstrate that measurement of serum KL-6 was a useful marker to evaluate the activity of acute interstitial pneumonia associated with PM/DM.