Monoclonal antibodies against plasminogen and alpha-2-antiplasmin: binding to native and modified antigens

Two monoclonal antibodies against plasminogen and two against alpha-2-antiplasmin were characterized regarding their binding properties towards their respective native and modified antigens and towards the plasmin-alpha-2-antiplasmin complex. Using an ELISA system, the two monoclonal antibodies against plasminogen (MPW1PG, MPW2PG), reacted equally well with purified Glu-plasminogen; binding of one (MPW1PG) to the purified plasmin-alpha-2-antiplasmin complex was, however, more than three orders of magnitude weaker than that of the other. Similarly, both antibodies against alpha-2-antiplasmin (MPW2AP, MPW3AP) reacted equally well with native alpha-2-antiplasmin but binding of MPW3AP to the plasmin-alpha-2-antiplasmin complexes was more than one order of magnitude weaker than that of the other. These results were confirmed by immunoblotting by which it was made evident that the antiplasminogen antibody MPW1PG reacted only with the free or complexed Glu-form of plasminogen or plasmin, while MPW2PG reacted equally well with the Glu- and Lys-form. The alpha-2-antiplasmin antibody MPW2AP reacted with native and complexed alpha-2-antiplasmin while MPW3AP reacted only with the native antigen and with a 8,000 dalton cleavage product of the complex.