Inhibitory anti-factor V antibodies bind to the factor V C2 domain and are associated with hemorrhagic manifestations.


Journal Article

Factor V inhibitors may develop as spontaneous autoantibodies, as alloantibodies after exposure to bovine thrombin preparations, or in factor V-deficient patients after plasma therapy. Clinical manifestations range from asymptomatic laboratory abnormalities to life-threatening hemorrhage. We have characterized the anti-factor V antibodies from 12 patients diagnosed with factor V inhibitors. In 8 patients, hemorrhagic complications (5 autoantibodies and 3 bovine thrombin-induced alloantibodies) developed, and 4 were asymptomatic (2 autoantibodies and 2 alloantibodies). The IgG fractions from all 12 patients immunoprecipitated the factor Va light chain, but only the 8 IgG fractions associated with hemorrhage inhibited factor V activity in a prothrombinase assay. Nine IgG fractions, including the 8 patients with hemorrhage, immunoprecipitated the isolated second C-type domain (C2). The 8 IgG fractions from the symptomatic patients also immunoprecipitated recombinant chimeras containing only the N-terminal third of the factor V C2 domain, and isolated recombinant C2 domain abrogated the inhibitory effect of the antibodies. Five of the inhibitory IgG fractions blocked binding of factor V to phosphatidylserine. These results suggest that inhibitory anti-factor V antibodies are associated with hemorrhagic manifestations and frequently bind to a common region within the C2 domain, whether originating spontaneously or after exposure to bovine thrombin.

Full Text

Duke Authors

Cited Authors

  • Ortel, TL; Moore, KD; Quinn-Allen, MA; Okamura, T; Sinclair, AJ; Lazarchick, J; Govindan, R; Carmagnol, F; Kane, WH

Published Date

  • June 1, 1998

Published In

Volume / Issue

  • 91 / 11

Start / End Page

  • 4188 - 4196

PubMed ID

  • 9596666

Pubmed Central ID

  • 9596666

International Standard Serial Number (ISSN)

  • 0006-4971


  • eng

Conference Location

  • United States