Collagen-Platelet Interactions: Evidence for a Direct Interaction of Collagen With Platelet GPIa/IIa and an Indirect Interaction With Platelet GPIIb/IIIa Mediated by Adhesive Proteins

• Published in: Blood Vol. 74; no. 1; pp. 182 - 192
• Main Authors: Coller, Barry S., Beer, Juerg H., Scudder, Lesley E., Steinberg, Mark H.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01.07.1989; The Americain Society of Hematology
• Subjects: Antibodies, Monoclonal; Biological and medical sciences; Blood coagulation. Blood cells; Blood Platelets - physiology; Cell Adhesion; Chromatography, Affinity; Collagen - physiology; Flow Cytometry; Fundamental and applied biological sciences. Psychology; Humans; Immunologic Techniques; In Vitro Techniques; Molecular and cellular biology; Platelet; Platelet Aggregation; Platelet Membrane Glycoproteins - isolation & purification; Platelet Membrane Glycoproteins - physiology; Receptors, Cell Surface - physiology; Aggregation; Human; Flow cytometry; Platelet; Antigenic determinant; Radiolabelling; Collagen; Molecular interaction; Monoclonal antibody; Inhibition; Blood plasma; Biological receptor
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V74.1.182.182

Using intact human platelets as the immunogen and a functional, collagen-coated bead agglutination assay, we have produced a murine monoclonal antibody (6F1) that blocks the interaction between platelets and collagen in the presence of Mg++ . 6F1 affinity-purified the platelet glycoprotein la/Ila complex, and approximately 800 molecules of 6F1 bound per platelet at saturation. 6F1 nearly completely inhibited collagen-induced platelet aggregation and inhibited platelet adhesion to collagen by >95% when plasma proteins were absent. Antibody 10E5, which blocks the binding of adhesive glycoproteins to GPIIb/IIIa, produced only minor inhibition (~25%) of adhesion under the same circumstances. In contrast, when tested in plateletrich plasma (PRP), 6F1 had only a minor effect on collagen- induced platelet aggregation, prolonging the lag phase but not the slope or maximum aggregation. Similarly, when collagen was precoated with plasma, 6F1 caused less inhibition of platelet adhesion (53%) than without the precoating (>95%). Antibody 10E5 inhibited this adhesion by 32%, and the combination of 6F1 and 10E5 was more effective than either alone, inhibiting it by 90%. Time course studies of platelet agglutination of collagen-coated beads using PRP containing physiologic concentrations of divalent cations showed early inhibition by 6F1, indicating that the GPIa/IIa receptor operates in this environment. With more prolonged incubation, however, 6F1 was less effective; this later agglutination could be partially prevented by adding 10E5 or PGE1 to the 6F1. These data support a model wherein collagen can directly interact with GPIa/IIa and can indirectly interact with GPIIb/IIIa via intermediary adhesive proteins. The physiological significance of these interactions, and potential interactions with other receptors, remains to be established.