Evidence that plasma fibrinogen and platelet membrane GPIIb-IIIa are involved in the adhesion of platelets to an artificial surface exposed to plasma

We investigated the molecular mechanism(s) by which platelets adhere to an artificial surface exposed to plasma, using polystyrene microtiter plates pretreated with plasma. Washed platelets labelled with ⁵¹Cr were incubated with the plates under static conditions. Prostaglandin E₁(PGE₁) was added to the platelets to prevent platelet-platelet interactions. Adhesion required the presence of a divalent cation such as Mg⁺⁺ or Ca⁺⁺. Polyclonal anti-fibrinogen antibody inhibited adhesion by 70%. Polyclonal antibodies against fibronectin, vitronectin, von Willebrand's Factor, and the Fc portion of human IgG, had no effect on adhesion. Platelets adhered normally to a surface pretreated with plasma from a patient with severe von Willebrand's disease. No platelet adhesion occurred when the surface was pretreated with an afibrinogenemic plasma. Monoclonal antibodies against platelet membrane GPIIb-IIIa, potent inhibitors of ADP-induced fibrinogen binding to platelets, completely inhibited adhesion. Monoclonal antibodies against the GPIbα subunit and GPIc(VLA α₅) showed no inhibitory effects on adhesion. Platelets from a patient with Glanzmann's thrombasthenia (type 1) did not adhere to the surface pretreated with normal plasma. These results suggest that plasma fibrinogen adsorbed onto the surface and that platelet membrane glycoprotein(GP)IIb-IIIa were responsible for adhesion in an activation-independent manner.