Binding of high-avidity anti-beta2-glycoprotein I antibodies

Rheumatology (Oxford). 2004 Nov;43(11):1353-6. doi: 10.1093/rheumatology/keh349. Epub 2004 Jul 27.


Objectives: We studied the influence of different binding conditions on the interaction between high- or low-avidity IgG anti-beta2-glycoprotein I antibodies (anti-beta2-GPI) and beta2-GPI, which was either free in solution or bound to microtitre plates or nitrocellulose membranes.

Methods: Sera from 30 patients with antiphospholipid syndrome and/or systemic lupus erythematosus were selected on the basis of anti-beta2-GPI positivity. Avidity of IgG anti-beta2-GPI was determined by chaotropic ELISA, using increased NaCl concentration during the antibody binding. Immunodetection on nitrocellulose membrane followed reducing or non-reducing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (PAGE) of beta2-GPI. In converted, non-reducing PAGE, the preparation with high-affinity Fab fragments (obtained by papain digestion) was subjected to electrophoresis, while purified beta2-GPI was used as the sample in immunodetection.

Results: Anti-beta2-GPI antibodies of high, low or heterogeneous (low and high) avidity were found in 5/30, 9/30 and 16/30 sera, respectively. The density of beta2-GPI, which was 20-30 times higher on the nitrocellulose membrane than on the surface of ELISA plates, was not sufficient for the recognition of the antigen by anti-beta2-GPI: 2/5 high-avidity samples reacted only with non-reduced beta2-GPI, 3/9 low-avidity samples recognized only denatured and reduced beta2-GPI, and 1/16 samples with heterogeneous-avidity antibodies reacted with reduced and non-reduced beta2-GPI.

Conclusions: Our results suggest that neither high density of the antigen nor high avidity of the antibodies (or Fab fragments) alone was sufficient for the binding of anti-beta2-GPI to beta2-GPI. Some conformational modifications and, consequently, exposed neo-epitopes are required for the recognition of beta2-GPI by polyclonal anti-beta2-GPI antibodies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibody Affinity
  • Antigen-Antibody Reactions
  • Antiphospholipid Syndrome / immunology*
  • Autoantibodies / blood*
  • Autoantigens / immunology
  • Glycoproteins / immunology*
  • Humans
  • Immunoglobulin Fab Fragments / immunology
  • Immunoglobulin G / blood
  • Lupus Erythematosus, Systemic / immunology*
  • beta 2-Glycoprotein I


  • Autoantibodies
  • Autoantigens
  • Glycoproteins
  • Immunoglobulin Fab Fragments
  • Immunoglobulin G
  • beta 2-Glycoprotein I