Antigenic structures recognized by anti-β2-glycoprotein I auto-antibodies

Hideki Kasahara, Eiji Matsuura, Keiko Kaihara, Daisuke Yamamoto, Kazuko Kobayashi, Junko Inagaki, Kenji Ichikawa, Akito Tsutsumi, Shinsuke Yasuda, Tatsuya Atsumi, Tatsuji Yasuda, Takao Koike

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


β2-Glycoprotein I (β2-GPI) is a major antigen for anti-cardiolipin antibodies and their epitopes are cryptic. Conformation of each domain of β2-GPI was optimized from its crystal structure by energy minimization and by molecular dynamics simulation. Three electrostatic interactions, i.e. D193-K246, D222-K317 and E228-K308, were observed between domains IV and V in the optimized structure that was constructed based on the consensus sequences obtained by the phage-displayed random peptide library. Antigenic structures determined by the epitope mapping mainly consisted of hydrophobic amino acids located on two discontinuous sequences in domain IV. These amino acid clusters, as an epitope, were covered by domain V and were of a hidden nature. A similar but incomplete counterpart to the epitopic clusters was found in domain I but was not in domains II or III. Binding of anti-β2-GPI auto-antibodies to solid-phase β2-GPI was significantly reduced either by L replacement for W235, a common amino acid component for the epitopes, or by V replacement for all of D193, D222 and E228. Structural analysis indicated a hypothesis that these electrostatic interactions between domains IV and V retained exposure to W235 and that epitope spreading occurred in the region surrounding W235. Thus, epitopic structures recognized by anti-β2-GPI auto-antibodies are cryptic and inter-domain electrostatic interactions are involved in their in exposure.

Original languageEnglish
Pages (from-to)1533-1542
Number of pages10
JournalInternational Immunology
Issue number12
Publication statusPublished - Dec 2005


  • Anti-phospholipid antibody
  • Anti-phospholipid syndrome
  • B cell epitope

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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