A novel anionic modification of N-glycans on mammalian endothelial cells is recognized by activated neutrophils and modulates acute inflammatory responses

We previously reported an unusual carboxylated modification on N-glycans isolated from whole bovine lung. We have now raised Ig: mAbs against the modification by immunization with biotinylated aminopyridine-derivatized glycans enriched for the anionic species and screening for Abs whose reactivities were abrogated by carboxylate neutralization of bovine lung glycopeptides, One such Ab (mAb GB3.1) was inhibited by carboxylated bovine lung glycopeptides and other multicarboxylated molecules, but not by glycopeptides in which the carboxylate groups were modified. The Ab recognized an epitope constitutively expressed on bovine, human, and other mammalian endothelial cells. Stimulated, but not resting, neutrophils bound to immobilized bovine lung glycopeptides in a carboxylate-dependent manner. The binding of activated neutrophils to immobilized bovine lung glycopeptides was inhibited both by mAb GB3.1 and by soluble glycopeptides in a carboxylate-dependent manner. The Ab also inhibited extravasation of neutrophils and monocytes in a murine model of peritoneal inflammation. This inhibition of cell trafficking correlated with the increased sequestration but reduced transmigration of leukocytes that were found to be adherent to the endothelium of the mesenteric microvasculature, Taken together, these results indicate that these novel carboxylated N-glycans are constitutively expressed on vascular endothelium and participate in acute inflammatory responses by interaction with activated neutrophils.