Potential application of labeled antibodies for thrombus detection.

Labeling platelets with monoclonal antibodies in whole blood for imaging thrombi is less cumbersome than the established 111In-oxine method.. 7E3, a murine monoclonal antibody directed against glycoprotein IIb and/or IIIa on both human and dog platelets was used to label canine platelets. Thrombi were induced by transcatheter placement of a copper coil followed by electrocoagulation. 7E3 was iodinated with 131I and labelled with 111In using 7E3-DTPA conjugate. Whole blood was incubated with 0.5-1.0 micrograms labeled 7E3/mL blood. In 4/4 dogs, experimental deep vein thrombi were identified using both 131I- and In 1/3 dogs, experimental coronary thrombus could be identified ex vivo at 4 h. Clot to blood ratios ranged between 7 to 13:1. Using the 111In-oxine method, 0/3 coronary thrombi were seen. Thus, 131I- and 111In-labeled 7E3 may be used to readily identify peripheral venous thrombi. For reliable and prompt identification of coronary thrombi, more rapid clearance of the labeled platelets is required.