Immunopurification of human β2-glycoprotein I with a monoclonal antibody selected for its binding kinetics using surface plasmon resonance biosensor

The beta(2)-glycoprotein I (beta(2)GPI)-binding properties of five murine monoclonal antibodies immobilized as capture antibodies were studied using surface plasmon resonance detection. The monoclonal antibody with the fastest dissociation kinetics (6F3) was selected for the development of an immunoaffinity chromatography procedure, assuming that its behaviour would be similar in both systems since the covalent coupling chemistries involved amino groups in both cases. Under our experimental conditions of a fast one-step procedure, beta(2)GPI was purified to homogeneity from human plasma with a yield of about 50%. beta(2)GPI was eluted under fairly mild conditions, either at low pH or at high pH. The immunoadsorbent was used five times without any apparent loss of binding capacity. The immunopurified protein showed similar binding to cardiolipin-coated polystyrene wells as beta(2)GPI purified by conventional methods. However, differences in the pattern of immunoreactivity in relation to the purification procedure were observed by surface plasmon resonance using the monoclonal antibody with the highest association kinetics (9G1) immobilized on the sensor surface. (C) 1998 Elsevier Science B.V.