Identification and characterization of antibodies that bind GPIIb/IIIa: antagonist complexes.
A potential limitation of anti-thrombotic therapies directed at platelet GPIIb/IIIa is immune mediated thrombocytopenia. Reagents that mimic the behavior of patient antibodies would provide a valuable tool for studies directed at understanding the basis of the immune mechanism involved in GPIIb/IIIa antagonist induced thrombocytopenia. Such reagents would bind epitopes that are exposed when the conformation of the receptor is modified in response to inhibitor binding. We describe the production and characterization of monoclonal antibodies that were raised against platelet GPIIb/IIIa bound to a potent antagonist, XP280. These antibodies have high affinity and specificity for XP280 bound GPIIb/IIIa using either purified protein or human platelets. We have demonstrated that the antibodies recognize a conformationally altered form of the receptor, that both subunits are required for binding, and that the antagonist itself does not form part of the binding epitope. Competition experiments indicate that multiple drug-dependent epitopes are exposed on the receptor in response to antagonist binding. The antibodies bind with high specificity to some but not all GP IIb/IIIa/antagonist complexes indicating that different conformational epitopes are exposed when GP IIb/IIIa is bound to different antagonists.
Breth
Leah
L
Departments of Cardiovascular Disease Biology, Discovery Chemistry, and Applied Biotechnology, Pharmaceutical Research Institute, Bristol-Myers Squibb Company, 311 Pennington Rocky Hill Rd, Pennington, NJ 08534, United States.
Kochie
Jennifer
J
Combs
Amanda
A
Wang
Shuaige
S
Smallheer
Joanne
J
Billheimer
Jeffrey
J
Seiffert
Dietmar
D
Hollis
Gregory
G
O'Neil
Karyn
K
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D015394:Molecular Structure; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors* / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000939:Epitopes; D019039:Platelet Glycoprotein GPIIb-IIIa Complex