Molecular identification of the cross-reacting epitope on alphaM beta2 integrin I domain recognized by anti-alphaIIb beta3 monoclonal antibody 7E3 and its involvement in leukocyte adherence.
The monoclonal antibody (mAb) 7E3 directed to the platelet integrin alphaIIb beta3 was tested for its cross-reactivity with the homologous leukocyte integrin alphaM beta2. Nested recombinant fragments of alphaM I domain were expressed as glutathione S-transferase fusion proteins and analyzed for antibody recognition. In enzyme-linked immunosorbent assay, mAb 7E3 bound alphaM I domain fragments containing the amino-terminal sequence Cys128-Ser172, whereas the carboxyl-terminal region Leu173-Pro291 was ineffective. A synthetic peptide designated R1.1 and duplicating the alphaM sequence G127CPQEDSDIAFLIDGSGSIIPHDF150 bound mAb 7E3. In contrast, the adjacent alphaM region F150RRMKEFVSTVMEQLKKSKTLFS172 or a control peptide with a scrambled R1.1 sequence was not recognized by mAb 7E3. Binding of mAb 7E3 to alphaM I domain blocked monocyte and neutrophil adhesion to immobilized fibrinogen and fibrinogen-dependent leukocyte-endothelium bridging, indistinguishably from bona fide anti-beta2 mAb IB4. In contrast, leukocyte binding to stable transfectants expressing intercellular adhesion molecule-1 was not affected by mAb 7E3. Balloon-mediated injury of iliofemoral arteries in rabbits resulted in prominent deposition of fibrinogen and increased monocyte adhesion to the injured vessel, in a reaction inhibited by mAb 7E3, but unaffected by control mAb 14E11. Through its cross-reactivity between alphaIIb beta3 and alphaM beta2, mAb 7E3 may initiate a new class of integrin antagonists, capable of simultaneously targeting platelet and leukocyte adhesion mechanisms in vascular injury.
Department of Pathology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
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Plescia
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Conte
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VanMeter
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Ambrosini
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Altieri
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001158:Arteries / Q000473:pathology; D002448:Cell Adhesion / Q000502:physiology*; D003429:Cross Reactions / Q000276:immunology; D018604:Epitope Mapping; D000939:Epitopes / Q000737:chemistry*; D005340:Fibrinogen / Q000276:immunology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology; D016209:Interleukin-8; D007962:Leukocytes / Q000502:physiology*; D016177:Macrophage-1 Antigen / Q000737:chemistry* / Q000276:immunology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology*; D011485:Protein Binding / Q000276:immunology; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics
D000911:Antibodies, Monoclonal; D000939:Epitopes; D016209:Interleukin-8; D016177:Macrophage-1 Antigen; D010446:Peptide Fragments; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011994:Recombinant Proteins; D018799:Intercellular Adhesion Molecule-1; D005340:Fibrinogen