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Monovalent binding of autoantibodies to β 2 ‐glycoprotein I, detected using surface plasmon resonance at low antigen density

2000; Wiley; Volume: 109; Issue: 1 Linguagem: Inglês

10.1046/j.1365-2141.2000.01976.x

1365-2141

Véronique Regnault, Emmanuel de Maistre, Denis Wahl, Thomas Lecompte,

Complement system in diseases

The precise mechanism of interaction between autoantibodies and β 2 ‐glycoprotein I (β 2 GPI) and the experimental conditions to be used for their detection are still under debate. Until now, these interactions have been studied under static conditions. We have investigated the interactions of purified IgG from 25 lupus anticoagulant‐positive patients with immobilized β 2 GPI under flow conditions by real‐time analysis based on surface plasmon resonance technology. Sensor chips were coated with purified human β 2 GPI coupled to dextran via amino groups at low densities (1·4, 1·8 or 2·4 ng β 2 GPI/mm 2 ). Four patients' IgG displayed efficient binding and had the highest so‐called antiphospholipid IgG levels by enzyme‐linked immunosorbent assay (ELISA) and the highest absorbance values in an anti‐ β 2 GPI ELISA at a β 2 GPI density reported to be around 12 ng/mm 2 . Binding of antibodies to the β 2 GPI sensor chips proved to be dependent upon the IgG concentration and β 2 GPI density and was inhibited by a rabbit antibody against β 2 GPI. Similar association and dissociation profiles were observed for the four efficient binders. The fast rate of dissociation limited the binding of autoantibodies to β 2 GPI and was highly suggestive of a monovalent association, confirmed by binding of Fab fragments under similar experimental conditions. In conclusion, monovalent binding of low‐affinity antibodies to β 2 GPI immobilized at a density as low as 1·8 ng/mm 2 could be detected using surface plasmon resonance.