Human Plasminogen Activation is Blocked by Monoclonal Antibody
An H4 monoclonal antibody that selectively binds to plasminogen (PLG), but not to mini-plasmin has been obtained. This selectivity probably results from the interaction between the antibody and the PLG activation site. The antibody sharply blocks the PLG activation by urokinase-type (uPA) or tissue (tPA) PLG activator. The activation is not blocked by the control G8 antibody which equally binds to PLG and mini-plasmin. The H4 antibody is specific to human PLG; the rabbit PLG activation is not inhibited. The H4 antibody disrupts the cycle of the mutual activation of PLG and uPA: both uPA-dependent PLG activation and PLG-dependent pro-uPA activation are blocked. Thus, in the presence of the H4 antibody, pro-uPA is not activated by plasmin in a mixture of PLG, pro-uPA and activated uPA, which makes it possible to measure in this mixture of the activated uPA concentration.