β2-glycoprotein I:: Target antigen for 'antiphospholipid' antibodies.: Immunological and molecular aspects

It has become clear that beta(2)-glycoprotein I (beta(2)GPI) is the most common and best-characterised antigenic target for 'antiphospholipid' (aPL) autoantibodies. These antibodies preferentially bind beta(2)GPI that has been immobilised on anionic phospholipid membranes or certain synthetic surfaces. These surfaces appear to act by increasing antigen density to allow binding of intrinsically low-affinity anti-beta(2)GPI autoantibodies. Binding of beta(2)GPI in fluid phase is weak and requires high concentrations of beta(2)GPI. Our understanding of the pathophysiology of the 'Antiphospholipid' Syndrome (APS) has increased exponentially with the number of studies into the interactions of aPL antibodies and beta(2)GPI.