Summary

The newly identified platelet collagen receptor glycoprotein VIbinds to fibrous collagen, inducing platelet activation. Severalantibodies against GPVI have been reported, including apatient’s auto-antibodies, that activates platelets through theirability to crosslink this glycoprotein. We have developed amonoclonal antibody (mAb) against GPVI using the recombinantextracellular domain of GPVI as an antigen. This antibody,mAb 204-11, induced platelet aggregation and tyrosine phosphorylationof proteins similar to those induced by GPVI-reactiveproteins, collagen and convulxin. Its interaction with GPVI was analyzed by measuring the effect of the antibody on GPVIbinding to collagen using a dimeric form of recombinant GPVI,GPVI-Fc₂. MAb 204-11 inhibited the binding of GPVI-Fc₂ tofibrous collagen particles, but enhanced the GPVI binding toimmobilized collagen, suggesting that the antibody binds to aregion near the collagen binding site of GPVI. MAb 204-11 alsoinhibited the GPVI binding to convulxin at a low concentration,but not completely. Since mAb 204-11 reacts specifically withGPVI and is applicable for immunoblotting and immunoprecipitation,this antibody would be useful for studies on GPVI.