Summary
The two urokinase preparations currently undergoing clinical trials in the United States [Abbott urokinase (UK-A) and Sterling-Winthrop urokinase (UK-SW)] were compared immunologically using an antiserum prepared against UK-SW. Based on a previously described designation system, 2 components (III and IV) were found to be common to both preparations while the other two (I and II) detected by the antiserum were found only in UK-SW.
In order to relate functional activity to the immunological reactions seen in immunodiffusion and immunoelectrophoresis, inhibition titrations were carried out with simultaneous qualitative testing of the antigen-antibody mixtures. Two inflection points on the inhibition curve were correlated with the appearance of components III and IV in antigen excess or at equivalence. In the case of one globulin preparation (710) no plateau effect was observed, and components III and IV appeared in antigen excess at the same time.
The results of these studies indicate that 2 active components are present in both UK-A and UK-SW. These two are the components designated III and IV and are common to both preparations. The difference in equivalence points for these two components and those for inactive I and II make it possible to precipitate I and II completely while III and IV are in antigen excess, thus providing a reagent for identifying urokinase of either III- or IV- specificity in other samples.
