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.
