A MONOCLONAL-ANTIBODY PREVENTING BINDING OF TISSUE-TYPE PLASMINOGEN-ACTIVATOR TO FIBRIN - USEFUL TO MONITOR FIBRINOGEN BREAKDOWN DURING T-PA INFUSION

  • 1 May 1986
    • journal article
    • research article
    • Vol. 67  (5) , 1482-1487
Abstract
One (MA-1C8) of 36 monoclonal antibodies obtained by fusion of P3X63-Ag8-6.5.3 myeloma cells with spleen cells of mice immunized with purified human tissue-type plasminogen activator (t-PA) blocked the activity of t-PA on fibrin plates but not on chromogenic substrates. MA-1C8 at a concentration of 200 .mu.g/mL inhibited plasma clot lysis and bindig of t-PA to the clot. MA-1C8 had no influence on the activation of plasminogen by t-PA, which obeys Michaelis-Menten kinetics with Km = 105 .mu.mol/L and kcat = 0.05 s-1; however, it abolished the influence of CNBr-digested fibrinogen on Km. These findings confirm that the stimulatory effect of fibrin on the activation of plasminogen by t-PA is mediated by binding of t-PA to fibrin and provide additional support for the kinetic model. Addition of t-PA to pooled fresh human plasma to a concentration of 5 .mu.g/mL resulted in extensive fibrinogen breakdown after incubation for one hour at 37.degree. C or during storage at -20.degree.) C for one day. In both instances, fibrinogen degradation was completely prevented by addition of MA-1C8 to a concentration of 200 .mu.g/mL of plasma. MA-1C8 also effectively prevented in vitro fibrinogen degradation and in vitro plasminogen activation in plasma samples obtained during infusion of recombinant t-PA in patients with thromboembolic disease. Thus, MA-1C8 is a useful tool for discriminating between in vivo and in vitro fibrinolysis during thrombolytic therapy with t-PA.

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