Biosensor Analysis of β2-Glycoprotein I–Reactive Autoantibodies: Evidence for Isotype-Specific Binding and Differentiation of Pathogenic from Infection-Induced Antibodies

Abstract Background: For the laboratory diagnosis of the antiphospholipid syndrome (APS) we developed a biosensor with the ability to distinguish between disease-relevant anti-β2-glycoprotein I (β2GPI) autoantibodies (anti-β2GPI) and pathogen-specific β2GPI cross-reactive antibodies that occur transiently during infections. Methods: We used a surface plasmon resonance (SPR) biosensor device. For the detection of anti-β2GPI in serum samples, affinity-purified human β2GPI was covalently attached to a functionalized n-alkanethiol self-assembling monolayer on the biosensor chip. After verifying the specificity of the biosensor system with a panel of monoclonal antibodies to β2GPI, we analyzed s…