[Application of a monoclonal antibody SZ-51 specific for activated human platelets in canine thrombosis imaging].

To detect specifically the localization of thrombus in vivo, we prepared a monoclonal antibody (McAb) SZ-51 specific for an alpha-granule membrane protein (GMP-140) exposed on the surface of activated human platelets. 131I labeled SZ-51 antibody combined preferentially with thrombus induced by thrombin in vitro. Owing to McAb SZ-51 crossreaction with the activated platelets of dogs, thrombi in both femoral artery and vein were prepared and imaged with SPECT in dogs. The ratio of radioactivity between thrombi and blood pool was significantly increased in both arterial and venous thrombus after injection of 131I-SZ-51, especially at the 4th hour. Moreover, the imaging of arterial thrombus is better than that of venous thrombus. However, both arterial and venous thrombi could not be imaged by the injection of 131I-nonimmune IgG. These findings were in agreement with the radioactivity ratios between the removed thrombi and blood 24 hours after injection. Therefore, these results indicate that McAb SZ-51 has the power of detecting thrombi in vivo.