Inhibition of plasma tPA activity by immunoglobulins purified from the plasma of 2 patients. The tPA activity was measured in a healthy control's plasma after 1 hour of incubation at 37°C with increasing amounts of immunoglobulins purified from the plasma of patients no. 1 and 2. Immunoglobulins purified from a healthy subject served as negative control and goat anti-tPA antibodies served as positive control. Results are expressed as IU/mL tPA activity.