Binding of biotinylated fibrinogen to srGPIIb-IIIa (A) and platelet GPIIb-IIIa (B). Fibrinogen reacted spontaneously with srGPIIb-IIIa and this binding was enhanced slightly by the LIBS MoAb AP5. Binding to platelet GPIIb-IIIa occurred only when AP5 was added. In both cases, fibrinogen binding was completely inhibited by RGDS peptide. Data points are the average of triplicate determinations, which varied from each other by no more than ±5%.