Mouse PECAM-1 binding properties of scFv/uPA-T. (A) ELISA: binding of anti–PECAMscFv/uPA-T and free lmw-scuPA to immobilized soluble mouse PECAM. (B) Inhibition of binding of fusion protein to soluble mouse PECAM by parental anti–PECAM IgG. (C) Thrombin-mediated release of the lmw-uPA-T moiety from PECAM-bound scFv/uPA-T. scFv/uPA-T was incubated with PECAM-immobilized wells and treated with thrombin as indicated in “Thrombin-mediated release of PECAM-bound fusion protein.” Error bars indicate standard error of the mean (SEM). (D) Amidolytic activity of scFv/uPA-T and lmw-scuPA bound to immobilized mouse PECAM after addition of thrombin. (E) Activation of plasminogen to plasmin by PECAM-associated scFv/uPA-T upon addition of thrombin. Error bars represent SEM.