Platelet Imaging in Man using Antiplatelet Monoclonal Antibodies

Radiolabeled platelets have been used in experimental imaging studies using the gamma camera to localize and quantify platelet accumulation. Conventional radiolabelling methods have been laborious, requiring specialized expertise and facilities. Recent advances in biotechnology have provided a number of murine monoclonal antibodies for the selective radiolabelling of circulating cells, cellular components and proteins. Most of these antibodies have been used for the in vitro study of platelet membrane structures. Relatively few antibodies have been administered to humans for in vivo imaging. Nevertheless, the use of monoclonal antibodies as a means of in vivo radiolabelling of platelets following a single intravenous injection represents a significant advance over the established techniques. Clinical studies currently underway have demonstrated that antibodies specific for platelets have the potential for replacing the conventional methods of radiolabelling and can result in images of outstanding quality. This paper reviews the current experimental and clinical studies using antibodies specific for platelets. In the main, these antibodies bind to the platelet membrane glycoprotein complexes IIb/IIIa or Ia/IIa. Recently, however, an antibody binding to P-selectin, and therefore specific to activated platelets, has been introduced and represents an interesting new development. The future application of this technology based on either humanized or synthetic molecules recognizing platelet antigens is likely to become routinely accepted for the study of platelet deposition in experimental settings and for thrombus imaging in clinical practice.