Expression of sialoadhesin on alveolar macrophages, a macrophage-restricted receptor

Purpose. Sialoadhesin (Sn) is known to play a role in scavenging function and in cellular interactions of macrophages. The objective of this work was to compare the expression level of Sn on alveolar macrophages (AM) and to compare it with Sn level on cell line and other tissue macrophage populations in normal and inflammatory situations. This study was carried out in order to determine the role of this lectine on AM surface. Methods. Sn expression levels on mouse AM and LPS-induced or untreated J774 cell line were evaluated using monoclonal antibodies specific for Sn. Labeled cells were analysed using fluorescence-activated cell sorter (FACS). Sn was induced on thioglycolate-elicited peritoneal macrophages (TPM) by cultivating cells in presence of mouse serum. Sn levels on TPM and resident peritoneal macrophages (RPM) were evaluated on rosetting assays with human red blood cells. Results. Sn was expressed on alveolar macrophages recovered by broncho-alveolar lavage whereas RPM did not show any level of Sn expression. When inflammation of peritoneal cavity was induced, TPM required the presence of mouse serum to show a high level of Sn. J774 cell line did not express Sn in both normal and inflammatory situations. Conclusion. In inflammatory situations, induction of Sn expression occurs to increase cells interactions of macrophages with immune cells. On AM surface, Sn seems to be mainly involved in cell-extracellular matrix interactions to allow the high motility of AM in basal condition.