Protein profile in bronchoalveolar lavage fluid from patients with sarcoidosis and idiopathic pulmonary fibrosis as revealed by SDS-PAGE electrophoresis and Western blot analysis

Abstract

Uebelhoer M, Bewig B, Oldigs M, Nowak D, Magnussen H, Petermann W, Barth J. Protein profile in bronchoalveolar lavage fluid from patients with sarcoidosis and idiopathic pulmonary fibrosis as revealed by SDS-PAGE electrophoresis and Western blot analysis. Scand J Clin Lab Invest 1993; 53: 617-623.

So far bronchoalveolar lavage (BAL)-protein in interstitial lung disease (ILD) is evaluated by measuring concentrations of single proteins. Due to the high dilution of most proteins in BAL, analysis of protein profile has been disappointing. This study describes a new method to overcome this problem and to reveal a highly differentiated picture of BAL proteins.

Eighteen patients with pulmonary sarcoidosis, 18 patients with idiopathic pulmonary fibrosis (IPF) and 22 patients with no clinical, roentgenologic or functional evidence of ILD underwent BAL. Total and differential cell count was performed. Normal values for the control group, a lymphocytic alveolitis in sarcoidosis and a granulocytic alveolitis in IPF-patients were found. Median total protein concentration in sarcoidosis showed an increase five times higher than that of the controls (150mgl^_1 and 27mgl∼¹, respectively) with p < 0.001, IPF protein concentration (58 mg 1^_1) exceeded twice the control values (0.01 > p > 0.001). Analysis of electrophoretic protein profile in controls with Western blot analysis and the biotin/streptavidin staining system revealed a highly differentiated range of bands. Staining with immunoglobulin antibody identified six bands. Four proteins with molecular weight < 21.000 dalton were present only in sarcoidosis patients. These proteins may be identical with fragmented serum proteins or different cell mediators detected in alveolar cell supernatants. Furthermore, in sarcoidosis the intensity and number of bands with molecular weight more than 67.000 dalton was increased. This gives strong evidence for an injury of the alveolar membrane integrity in the alveolitis during the course of sarcoidosis. The uniform protein profile in IPF compared to the highly variable profile and increased band intensity in sarcoidosis stresses the different pathogenesis of these ILDs.

Western blot analysis of BAL-protein profile is a highly promising method to assess pathogenetic changes, alveolar membrane integrity, and leakage in interstitial lung disease.

Key Words:

• bronchoalveolar lavage
• pulmonary fibrosis
• sarcoidosis
• proteins
• immunoglobulins
• fibronectin