EXPRESSION OF GLYCAM-1, AN ENDOTHELIAL LIGAND FOR L-SELECTIN, IS AFFECTED BY AFFERENT LYMPHATIC FLOW

The interaction of naive, L-selectin-bearing lymphocytes with counterr eceptors on the surface of high endothelial venules (HEV) is the initi al step in the extravasation of these cells from the bloodstream into the peripheral lymph node. Recently, two sulfated glycoprotein ligands , 50 and 90 kDa, respectively, have been identified as ligands for L-s electin using an L-selectin-IgG chimera. cDNA cloning of one of these molecules, the 50-kDa sulfated glycoprotein (glycosylation-dependent c ell adhesion molecule 1 [GlyCAM-1]), has shown it to be a mucinlike sc affold that presents a carbohydrate ligand(s) to the lectin domain of L-selectin. Herein, we analyze the factors that might regulate the exp ression of these ligands. Ligation of afferent lymphatics results in a complete loss of the mRNA for GlyCAM-1. In addition, L-selectin-media ted adhesion, as inferred by binding of an L-selectin-IgG chimera, is also lost on interruption of afferent flow. It thus appears that a sol uble and/or cellular component(s) of afferent lymph regulates the expr ession of GlyCAM-1 mRNA and the resultant HEV adhesiveness for lymphoc ytes.