Platelet-collagen adhesion: inhibition by a monoclonal antibody that binds glycoprotein IIb.
To identify platelet surface structures involved in adhesion to collagen, the effect of 16 murine antiplatelet membrane hybridoma antibodies were tested in a defined, in vitro assay. Four of these antibodies inhibited platelet-collagen adhesion and reacted with a polypeptide with Mr approximately 125,000, as determined by immunoblots after gel electrophoresis under reducing conditions. Through detailed studies with one of these antibodies, the monoclonal antibody PMI-1, the relevant antigen was identified as platelet glycoprotein IIb alpha, based upon (a) co-migration with this glycoprotein in two-dimensional gel electrophoresis and (b) co-purification by immunoaffinity chromatography with a protein with apparent Mr identical to that of glycoprotein III, under conditions in which glycoproteins IIb and III form a complex. Univalent antibody fragments prepared from monoclonal antibody PMI-1 inhibited greater than 80% of platelet-collagen adhesion, and inhibition was completely blocked by the immunopurified antigen. These results indicate that glycoprotein IIb participates in some aspect of platelet-collagen adhesion. In contrast, the purified antigen only partially neutralized a polyclonal antiserum that blocked platelet-collagen adhesion, to a maximum of approximately 25%, at saturating antigen concentrations. Thus, by these immunological criteria, glycoprotein IIb is not the only molecule involved in this process.
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D001792:Blood Platelets / Q000502:physiology*; D002846:Chromatography, Affinity; D003094:Collagen; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000032:analysis*; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis*; D008970:Molecular Weight; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins; D011863:Radioimmunoassay
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D006023:Glycoproteins; D008565:Membrane Proteins; D010980:Platelet Membrane Glycoproteins; D003094:Collagen