Novel chondroitin sulfate-modified ligands for L-selectin on lymph node high endothelial venules

Abstract

The migration of lymphocytes into lymph nodes via high endothelial venules (HEV) is dependent on the expression of L-selectin on the lymphocyte cell surface. HEV express several L-selectin ligands including CD34, GlyCAM-1, MAdCAM-1 and two sulfated glycoproteins (Sgp) of 200 kDa and 170 kDa which remain to be identified. In this investigation, labeling with sodium [35S]sulfate, which is incorporated into and forms part of the functional carbohydrate ligand, has been used to isolate and characterize macromolecular L-selectin ligands. High endothelial cells (HEC) cultured from rat lymph node HEV were shown to express ligands for L-selectin. HEC synthesized two groups of sulfated glycoproteins of 150 kDa and > 200 kDa, which were present in conditioned medium. These coeluted on anion exchange chromatography at 1.0-1.2 M NaCl and supported calcium-dependent L-selectin-mediated cell adhesion. In common with known L-selectin ligands, Sgp 150/> 200 were shown to be O-sialoglycoproteins; however, in contrast to other ligands, Sgp 150/> 200 contained chondroitin sulfate glycosaminoglycan modifications which were required for L-selectin recognition. Chondroitin sulfate-modified ligands for L-selectin were expressed at the HEC surface and by HEV in lymph nodes, suggesting that they may participate in lymphocyte interactions with HEV in vivo.