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.
Plescia
J
J
Department of Pathology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Conte
M S
MS
VanMeter
G
G
Ambrosini
G
G
Altieri
D C
DC
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