Two independent sets of monoclonal antibodies define neoepitopes linked to soluble ligand binding and leukocyte adhesion functions of activated alpha M beta 2.
The integrin alpha M beta 2 mediates a variety of events, adhesive, phagocytic, and inflammatory. Evidence has suggested that the functional events may be mediated by the "activated" conformational forms of alpha M beta 2 produced by appropriate stimulation of myeloid and monocytic lineage. The activation of alpha M beta 2 may be associated with new epitopes on alpha M beta 2, sites that may be related to the acquired receptor functions. Monoclonal antibodies were produced that preferentially bind neoepitopes expressed by activated alpha M beta 2. These anti-neo antibodies each inhibited three activation-associated specific receptor alpha M beta 2 functions, though to different extents. One set of anti-neo antibodies inhibited in a concordant manner the binding of factor X and of fibrinogen by > 90%, abolished the alpha M beta 2-initiated cellular coagulant response, and inhibited monocyte adhesion to unstimulated endothelial monolayers. A second set of anti-neo antibodies only diminished factor X and fibrinogen binding by approximately 40% to 50% but markedly suppressed Xa generation and only partially inhibited monocyte adherence to unstimulated endothelium. Concordance was observed between binding of factor X or fibrinogen and competence for leukocyte adhesion to unstimulated endothelium. Antibody competition assays segregated the anti-neo antibodies into the same two distinct sets, consistent with recognition of separate neoepitopes that are linked to alpha M beta 2 function. These data support the conclusion that the activated conformer of alpha M beta 2 that binds fibrinogen and factor X also mediates monocyte-endothelial interactions as well as the alternative cellular coagulation pathway.
Elemer
G S
GS
Department of Immunology/IMM-17, Scripps Research Institute, La Jolla, CA 92037.
Edgington
T S
TS
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001777:Blood Coagulation / Q000187:drug effects; D002448:Cell Adhesion; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D000939:Epitopes; D006801:Humans; D016023:Integrins / Q000276:immunology* / Q000502:physiology*; D007962:Leukocytes / Q000502:physiology*; D008024:Ligands; D009000:Monocytes / Q000502:physiology
D000911:Antibodies, Monoclonal; D000939:Epitopes; D016023:Integrins; D008024:Ligands