Expression of complement-related membrane proteins on lymphocytes and alveolar macrophages in bronchoalveolar lavage fluid

ABSTRACT Interstitial lung disease (ILD) can be separated into two groups: (i) that in which the causes are known; and (ii) that in which the etiologies have not been determined. Meanwhile, complement is essential for the inflammatory response and complement systems have been recognized as factors involved in organizing ILD. In the present study we investigated whether there were any differences in complement-related membrane proteins on lymphocytes and alveolar macrophages in bronchoalveolar lavage fluids (BALF) between different ILD. Bronchoalveolar lavage fluid samples were obtained from 12 patients and eight healthy individuals. Bronchoalveolar lavage fluid cells were incubated with monoclonal antibodies (mAbs) against C3b/C4b receptor (CR1), C3bi receptor (CR3), membrane cofactor protein (MCP) and decay accelerating factor (DAF) and were then labeled with fluorescein isothio-cyanate-conjugated anti-mouse IgG. Cells were analyzed using a flow cytometer.The results demonstrate for the first time that CR3 and DAF are elevated on alveolar macrophages, and that MCP and DAF are increased on BALF lymphocytes in sarcoidosis. The possible roles of complement-related membrane proteins in the pathogenesis of immune processes that are ongoing in sarcoidosis are still obscure, but our results may provide some useful information on the mechanisms underlying sarcoidosis.