AN EXPERIMENTAL SYSTEM FOR INVESTIGATION OF PENETRATION OF COMPONENTSOF THE FIBRINOLYTIC SYSTEM INTO A PLASMA CLOT

An experimental system is described that allows visualization and quan tification by means of fluorescence microscopy of the penetration of p roteins into a plasma clot. Localization of FITC-labelled proteins in the clot situated between two glass slides was monitored continuously without separation of the outer medium from the clot. Two strongly dif ferent modes of penetration were demonstrated for protein molecules wi thout affinity to fibrin, and for high affinity anti-fibrin(ogen) anti body. The latter was concentrated in a thin superficial layer of the c lot, its penetration inside the clot being decreased in comparison wit h freely diffusing molecules. The mode of penetration of two-chain uro kinase-type plasminogen activator into the clot was remarkably changed in the presence of bispecific antibody with an affinity for both urok inase and fibrin.