Neoantigenic expression in enzyme-inhibitor complexes. A means to demonstrate activation of enzyme systems.

Human thrombin-antithrombin III and plasmin-antiplasmin, two enzyme-inhibitor complexes composed of four different molecules, contain antigenic structures not present in the parent molecules, which can be directly quantitated in plasma with the use of non-cross-reacting antisera. It is anticipated that this neonatigenic expression is a more general phenomenon, which could provide a simple means of measuring activation of enzyme systems in biological fluids.