MONOCLONAL ANTIIDIOTYPIC ANTIBODY TO A POTENT THROMBOXANE-A2 RECEPTOR ANTAGONIST AND ITS INTERACTION WITH THROMBOXANE-A2 RECEPTOR

A monoclonal anti-idiotypic antibody that interacts with thromboxane A2 receptor was generated using an anti-idiotypic approach. Idiotypic antibodies against a potent receptor antagonist, HS-145, were generated in rabbit. The idiotypic antibodies were then selected by an affinity procedure using SQ29,548-Affi-Gel-102 matrix. The selected idiotypic antibodies were used as surrogate receptor for anti-idiotypic antibody generation. A mouse monoclonal antibody, 3D-9E-12, was generated. It was shown to displace I-125-HS-145 from affinity-purified idiotypic antibodies. It also inhibits I-125-IS-145 binding to thromboxane A2 receptor in human platelet membranes in a dose-dependent manner. Furthermore, it attenuated U46,619-induced increase in [S-35]guanosine 5'-O-(thiotriphosphate) binding and GTPase activity in human platelet membranes. Finally, it inhibited U46,619- but not PAF-induced platelet aggregation. These results indicate that 3D-9E-12 acts as a specific antagonist in the thromboxane A2 receptor.