Structure of a factor VIII C2 domain-immunoglobulin G4kappa Fab complex: identification of an inhibitory antibody epitope on the surface of factor VIII

Blood. 2001 Jul 1;98(1):13-9. doi: 10.1182/blood.v98.1.13.


The development of an immune response to infused factor VIII is a complication affecting many patients with hemophilia A. Inhibitor antibodies bind to antigenic determinants on the factor VIII molecule and block its procoagulant activity. A patient-derived inhibitory immunoglobulin G4kappa antibody (BO2C11) produced by an immortalized memory B-lymphocyte cell line interferes with the binding of factor VIII to phospholipid surfaces and to von Willebrand factor. The structure of a Fab fragment derived from this antibody complexed with the factor VIII C2 domain was determined at 2.0 A resolution. The Fab interacts with solvent-exposed basic and hydrophobic side chains that form a membrane-association surface of factor VIII. This atomic resolution structure suggests a variety of amino acid substitutions in the C2 domain of factor VIII that might prevent the binding of anti-C2 inhibitor antibodies without significantly compromising the procoagulant functions of factor VIII.

MeSH terms

  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / metabolism
  • Antigen-Antibody Complex / chemistry*
  • B-Lymphocytes / immunology
  • Binding, Competitive
  • Cell Line
  • Crystallography, X-Ray
  • Epitope Mapping
  • Factor VIII / immunology*
  • Hemophilia A / immunology
  • Humans
  • Immunoglobulin Fab Fragments / chemistry
  • Immunoglobulin Fab Fragments / isolation & purification
  • Immunoglobulin Fab Fragments / metabolism
  • Kinetics
  • Models, Molecular
  • Protein Binding
  • Protein Structure, Tertiary
  • von Willebrand Factor / metabolism


  • Antibodies, Monoclonal
  • Antigen-Antibody Complex
  • Immunoglobulin Fab Fragments
  • von Willebrand Factor
  • Factor VIII