The use of PhastSystem crossed immunoelectrophoresis with immunoblotting to demonstrate a complex between glycoprotein Ib and the actin‐binding protein (ABP) of human platelets

The study shows how a technique described in an accompanying paper can be applied to solve a biological problem. The technique makes use of the observation that a monoclonal antibody that has been coprecipitated with its antigen during crossed immunoelectrophoresis can be transferred to a nitrocellulose membrane and visualized. Previous studies using crossed immunoelectrophoresis of Triton X‐100 extracts of platelets have indicated that a particular immunoprecipitate (peak III) of the membrane receptor glycoprotein Ib (GP Ib) might contain a complex between the receptor and the actin‐binding protein (filamin). When a monoclonal antibody (PM6/ 317) directed towards the actin‐binding protein was added to a platelet extract prior to immunoelectrophoresis and blotting, this was visualized on the blot as a replica of the peak III immunoprecipitate. This demonstrates a colocalization of GP Ib and the actin‐binding protein in the precipitate, and thus the existence of a complex between the membrane receptor and the cytoskeletal protein.