Anti-platelet monoclonal antibody P256 in the diagnosis of renal transplant rejection.

Platelets labeled in vitro with In-111 have a recognized place in the diagnosis of renal transplant rejection. Following their introduction for imaging thrombi, radio-labeled anti-platelet antibodies may also have a role in the diagnosis of transplant rejection. Four of 11 patients with recently donated transplants had biopsy-proven acute rejection episodes close to the time of administration of In-111 P256 Fab' fragment, which recognizes the IIb-IIIa fibrinogen receptor on primate platelets. The transplant-to-background count rate at 3 and 24 hours after these injections were 2.2 (SE 0.14) and 2.3 (0.23), respectively, almost identical to the ratios, 2.0 (0.1) and 2.2 (0.11), recorded at the corresponding times after 19 injections of P256 Fab' that were remote in timing from rejection episodes. P256 Fab' may have value in the detection of postoperative venous thrombosis, but it has no value for the detection of transplant rejection.