BASIC SCIENCES Thrombus Imaging with Indium- 111 and Iodine-131-Labeled Fibrin-Specific Monoclonal Antibody and Its F(ab')2 and Fab Fragments

We have previously reported successful imaging of fresh (2-4 hr old) and aged (1-5 days old) canine thrombi with 131l-labeled intact monoclonal antibody (MAb) specific for fibrin. We now report thrombus imaging with 131l-labeled F(ab')2and Fab and 111ln-labeled intact MAb, F(ab')2, and Fab. lndium-111-labeled F(ab')2proved to be the best imaging agent due to less nonspecific binding in the liver than whole IgG. Image quality was improved by the higher administered dose permissible with "1ln and its better physical characteristics for imaging, compared to 131I.Immunofluorescence of fresh human histologie sections showed intact MAb and F(ab')2 binding to thrombi, pulmonary emboli, and atherosclerotic plaques, strengthening the feasibility of clinical thrombus imaging. J NucÃ-Med 29:1212-1222,1988 IVadi iioimmunoimaging of fresh and aged canine venous thrombi with iodine-131-(13'I) labeled fibrin-specific MAb T2Gls has proven successful (1,2). The antigenic site is between amino acids 15-22 on the beta-chain of human fibrin (3). Because this amino-termina