Reactions of DDAb2 with constructs 1 to 3 and platelet GPIIIa (Western blot). (Left) DDAb2 recognizes constructs 1 to 3 and platelet GPIIIa (Pl) in the presence of quinine. (Middle) DDAb2 fails to react with these targets in the absence of drug. (Right) Recognition of the same targets by monoclonal AP5 specific for the 5 N-terminal amino acids of GPIIIa.