Macrophages express cell surface laminin

Laminin, a non-collagenous extracellular connective tissue glycoprotein, was detected on the surface of mouse peritoneal macrophages. As determined by indirect immunofluorescence, as many as 60% of peritoneal macrophages elicited with thioglycollate expressed cell surface laminin. Only 14% of resident cells displayed detectable laminin. The expression of laminin increased with time post-injection. Concomitant with laminin expression, macrophages also displayed a receptor for the IB4 isolectin from Griffonia simplicifolia. This lectin, which binds methyl-alpha-D-galactopyranoside, may also react with the carbohydrate moeity of laminin. A small population of macrophages displayed both laminin and surface fibronectin. Unlike the difference in laminin expression between resident and thioglycollate-stimulated cells, there was no difference in cell surface fibronectin between these cell populations. Since laminin has been found to mediate cell attachment in other systems, expression of this molecule on the surface of stimulated macrophages may be important in cell-cell and cell-matrix adhesive properties of these cells.