KL-6, a mucin-like glycoprotein, in bronchoalveolar lavage fluid from patients with interstitial lung disease

Am Rev Respir Dis. 1993 Sep;148(3):637-42. doi: 10.1164/ajrccm/148.3.637.


KL-6, a mucin-like high-molecular-weight glycoprotein, is a serum marker indicating the disease activity of pneumonitis, such as idiopathic pulmonary fibrosis (IPF), hypersensitivity pneumonitis, and sarcoidosis. Immunohistochemical studies have shown that KL-6 is strongly expressed on Type 2 pneumocytes and also exists on epithelial cells in other organs. It has not been clarified whether the increased levels of KL-6 in sera from patients with pneumonitis are derived from the lower respiratory tract. In this study, KL-6 levels were evaluated in bronchoalveolar lavage fluid (BALF) samples from 9 healthy control subjects and 32 patients with interstitial pneumonitis. An abnormally high level of KL-6 in BALF was observed in 70% (7 of 10) of patients with IPF, 64% (9 of 14) of patients with sarcoidosis, and 100% (8 of 8) of patients with hypersensitivity pneumonitis but in none of the healthy control subjects. KL-6 levels in BALF were significantly correlated with numbers of total cells (p < 0.001), lymphocytes (p < 0.001), and neutrophils (p < 0.05) and with concentrations of albumin (p < 0.001) and total protein (p < 0.001) in BALF and, further, with serum KL-6 levels (p < 0.01). These results indicate that increased levels of serum KL-6 in patients with pneumonitis reflect the production levels of KL-6 derived from damaged or regenerating Type 2 pneumocytes in the lower respiratory tract.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alveolitis, Extrinsic Allergic / epidemiology
  • Alveolitis, Extrinsic Allergic / metabolism
  • Antigens / analysis*
  • Antigens, Neoplasm
  • Biomarkers / analysis
  • Bronchoalveolar Lavage Fluid / chemistry*
  • Bronchoalveolar Lavage Fluid / cytology
  • Cell Count
  • Chi-Square Distribution
  • Glycoproteins / analysis*
  • Humans
  • Lung Diseases / epidemiology
  • Lung Diseases / metabolism
  • Mucin-1
  • Mucins
  • Probability
  • Pulmonary Fibrosis / epidemiology
  • Pulmonary Fibrosis / metabolism*
  • Sarcoidosis / epidemiology
  • Sarcoidosis / metabolism


  • Antigens
  • Antigens, Neoplasm
  • Biomarkers
  • Glycoproteins
  • MUC1 protein, human
  • Mucin-1
  • Mucins