A novel regulatory epitope defined by a murine monoclonal antibody to the platelet GPIIb-IIIa complex (αIIbβ3 integrin)

Michihide Tokuhira, Makoto Handa, Tetsuji Kamata, Atsushi Oda, Masahiko Katayama, Yoshiaki Tomiyama, Mitsuru Murata, Yohko Kawai, Kiyoaki Watanabe, Yasuo Ikeda

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Abstract

We characterized a murine monoclonal antibody, PT25-2 (IgG1), raised against washed human platelets. The antibody and its Fab fragments were both capable of inducing platelet aggregation in a fibrinogen-dependent manner and induced 125I-fibrinogen binding to unstimulated platelets (120,000 molecules/platelet at a 100 nM IgG concentration). The antibody immunoprecipitated the αIIbβ3 complex from lysates of iodinated platelets but did not react with the respective subunits when complex formation was disrupted by treatment with 5 mM EDTA at 37°C for 30 min. However, simply removing the extracellular divalent cation with EDTA had no effect on antibody binding indicating that the antibody's epitope depends upon a conformational structure maintained by αβ subunit association. Antibody binding to unstimulated, washed platelets yielded binding parameters (K(d) = 40 nM, B(max) = 100,000 molecules/platelet), which were found to be virtually unchanged when binding was performed using thrombin or RGDS-peptide-stimulated platelets. Thus, the PT25-2 antibody defines a novel regulatory epitope expressed by the αIIbβ3 integrin on unstim ulated, quiescent platelets.

Original languageEnglish
Pages (from-to)1038-1046
Number of pages9
JournalThrombosis and Haemostasis
Volume76
Issue number6
Publication statusPublished - 1996 Dec 1

ASJC Scopus subject areas

  • Hematology

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    Tokuhira, M., Handa, M., Kamata, T., Oda, A., Katayama, M., Tomiyama, Y., Murata, M., Kawai, Y., Watanabe, K., & Ikeda, Y. (1996). A novel regulatory epitope defined by a murine monoclonal antibody to the platelet GPIIb-IIIa complex (αIIbβ3 integrin). Thrombosis and Haemostasis, 76(6), 1038-1046.