Avidity of anti-beta-2-glycoprotein I antibodies

• Published in: Autoimmunity reviews Vol. 4; no. 5; pp. 303 - 308
• Main Authors: Božič, B., Čučnik, S., Kveder, T., Rozman, B.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2005
• Subjects: Affinity; Animals; Anti-β2-GPI antibodies; Antibody Affinity - genetics; Autoantibodies - chemistry; Autoantibodies - metabolism; Avidity; beta 2-Glycoprotein I; Enzyme-Linked Immunosorbent Assay - standards; Glycoproteins - genetics; Glycoproteins - immunology; Humans; Pathogenicity; Standardisation; Pathogenicity; Standardisation; Affinity; Avidity; Anti-β2-GPI antibodies
• ISSN: 1568-9972; 1568-9972
• DOI: 10.1016/j.autrev.2005.01.001

The terms affinity and avidity are often used indiscriminately, despite clearly differing. Since affinity refers to monovalent binding of antibodies to a monovalent epitope, the majority of data on the binding of anti-β 2-glycoprotein I antibodies (anti-β2-GPI) characterized their avidity rather than affinity. Anti-β2-GPI were generally believed to be of low avidity, but heterogeneous avidity of patients' IgG anti-β2-GPI has been demonstrated. High avidity anti-β2-GPI monoclonals were reported to possess higher pathogenicity than low avidity anti-β2-GPI. Polyclonal high avidity anti-β2-GPI were found to be more common in patients with antiphospholipid syndrome (APS) and associated with thrombosis. Some conformational changes of β2-GPI are required for the binding of polyclonal anti-β2-GPI to the antigen: neither high density of the antigen nor high avidity of the anti-β2-GPI alone is sufficient for the recognition. Avidity of anti-β2-GPI should be considered in any attempt of inter-laboratory standardisation and/or evaluation of anti-β2-GPI enzyme-linked immunosorbent assay (ELISA).