[Use of avidin for speedy clearance of biotinylated immunoglobulins from the blood flow].

The phenomenon of a hundredfold more rapid blood clearance of biotinylated immunoglobulins after post-injection of an equiponderate dose of avidin is described. The concentration of 125I-labeled biotinylated IgG in rat circulation slowly decreased to 20% of the initial level in 24 hours. Avidin injection at any moment of this period induced a 90-95% reduction of blood radioactivity in 15 minutes. Up to 70% of the radioactivity was recovered in the liver. The technique of enhanced blood clearance developed in rats was checked in dogs using biotinylated monoclonal anti-human fibrinogen antibodies, capable of concentrating in dog thrombus. The results obtained offer the possibility of thrombus/blood contrast increase in radioimmunoimaging.