Determination of fibronectin and its degradation products in bronchoalveolar lavage fluid

Abstract

In order to estimate, in sarcoidosis, the extent of degradation and the availability of functionally active fibronectin (FN) in the alveolar space, native and total (=native+degraded) FN were determined in the bronchoalveolar lavage (BAL) fluid of 28 non-smoking patients with sarcoidosis, 12 healthy non-smokers and 24 asymptomatic smokers. The FN was measured in unconcentrated BAL fluid in the presence of the protease inhibitor aprotinin: total FN was assayed by a double-antibody sandwich enzyme-linked immunoadsorbent assay (ELISA) and native FN by a gelatin-antibody sandwich ELISA. Both in controls and in sarcoid patients, concentrations of native FN were lower than those of total FN, indicating that FN is degraded in the alveolar space. Compared to non-smoking controls, the sarcoid patients had significantly increased concentrations of both native and total FN (p<0.001 for both) in the BAL fluid. Native FN in percentage of total FN was similar in non-smoking sarcoids and controls, representing about 80% and 70%, respectively. In contrast, native FN corresponded to only 30% in the group of control smokers, indicating higher degradation in smokers. Thus, in smokers, less intact collagen-binding FN is available for forming an extracellular matrix, which may be necessary for repair. On the other hand, the elevation of FN, especially in its native form, in sarcoidosis implies that more of it may be available for repair but, if in excess, also for the build-up of fibrotic tissue. Both native and total FN were significantly correlated with albumin (p<0.001 for both) and lymphocytes (p<0.01 for both) in the BAL fluid of sarcoid patients, suggesting a close relationship between the production of FN and the inflammatory process in the alveoli.

Key Words:

• bronchoalveolar lavage
• degradation
• fibronectin
• sarcoidosis
• smoking