Antibodies Against the First Ig-Like Domain of Human Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1) That Inhibit PECAM-1-Dependent Homophilic Adhesion Block In Vivo Neutrophil Recruitment

Abstract

Platelet endothelial cell adhesion molecule (PECAM-1), a member of the Ig superfamily, is found on endothelial cells and neutrophils and has been shown to be involved in the migration of leukocytes across the endothelium. Adhesion is mediated, at least in part, through binding interactions involving its first N-terminal Ig-like domain, but it is still unclear which sequences in this domain are required for in vivo function. Therefore, to identify functionally important regions of the first Ig-like domain of PECAM-1 that are required for the participation of PECAM-1 in in vivo neutrophil recruitment, a panel of mAbs against this region of PECAM-1 was generated and characterized in in vitro adhesion assays and in an in vivo model of cutaneous inflammation. It was observed that mAbs that disrupted PECAM-1-dependent homophilic adhesion in an L cell aggregation assay also blocked TNF-α-induced intradermal accumulation of neutrophils in a transmigration model using human skin transplanted onto SCID mice. Localization of the epitopes of these Abs indicated that these function-blocking Abs mapped to specific regions on either face of domain 1. This suggests that these regions of the first Ig-like domain may contain or be close to binding sites involved in PECAM-1-dependent homophilic adhesion, and thus may represent potential targets for the development of antiinflammatory reagents.

Altered vascular permeability and early onset of experimental autoimmune encephalomyelitis in PECAM-1–deficient mice

“…This result may seem counterintuitive, given that several reports indicate that PECAM-1 is an important contributor to leukocyte transendothelial migration in vitro (13)(14)(15) and in vivo (16)(17)(18)(19). However, published data show that the requirement for PECAM-1 in the transmigration of leukocytes is not absolute.…”

Angiogenesis in Platelet Endothelial Cell Adhesion Molecule-1-Null Mice

“…[2][3][4][5][6] To determine whether PECAM-1-dependent ligand interactions might play a role in the ability of PECAM-1 to promote endothelial filopodia formation, we studied the effects of two functionally distinct antibodies: mAb 37, which blocks heterophilic binding; and mAb 62, which blocks both homophilic and heterophilic bindings. 49 We found that the initial formation of filopodia by HUVEC was suppressed by both antibodies but not by control IgG (Table 1). Given the functional properties of the antibodies (mAb 37 only blocks heterophilic binding) and the fact that these studies were done with non-confluent cells, these data suggest that endothelial cell filopodia formation may be mediated by PECAM-1-dependent heterophilic binding to matrix proteins.…”

Is PECAM-1 a Mechanoresponsive Molecule?

“…PECAM-1 is thought to play an important role in forming and maintaining the contact inhibited state of endothelial cells in culture as monolayer formation is inhibited by antibodies against the external portion of PECAM-1 (Albelda et al, 1990). In vivo, it is believed to mediate transmigration of white blood cells through the endothelium (Vaporciyan et al, 1993;Nakada et al, 2000).…”