Changes in bronchoalveolar lavage fluid proteins in sarcoidosis: a proteomics approach

In sarcoidosis, an inflammatory lung disease, the protein profile of bronchoalveolar lavage fluid (BALF) is altered. To study the BALF protein pattern changes in sarcoidosis, samples from six patients and four healthy individuals were analysed by two-dimensional polyacrylamide gel electrophoresis. A comparison of the protein-spot patterns showed a significantly higher number of protein spots in the pH range 5.5-6.7 in patients compared to controls (472 versus 384). Furthermore, the number of protein spots in the patients were significantly decreased in the acidic pH range 4.5-5.5 (399 versus 518). Measurement of the optical density in the gels showed varying expression levels for several protein spots. Seventeen of the altered protein spots were identified, of which seven have previously not been reported for BALF. Many of these are nonplasma proteins involved in the inflammatory and oxidant-antioxidant processes. In conclusion, the bronchoalveolar lavage fluid protein content is altered in sarcoidosis patients, especially for proteins that are not derived from plasma. The described proteomics approach will in the future be used to asses overall changes in the protein content associated with sarcoidosis and may offer the possibility of identifying disease-specific proteins.