DDAbs reacted in Western blots with human, but not rat, GPIIIa, and were blocked by monoclonal AP3.

(A) The 3 DDAbs recognized human (H), but not rat (R), GPIIIa in the presence, but not in the absence, of quinine. Monoclonal AP6 reacted with GPIIIa from both species regardless of whether the drug was present. (B) The drug-dependent reaction of DDAb 3 with human GPIIIa (lane 2) was blocked by monoclonal AP3 (lane 3), but not by AP5 (lane 4). Reactions of an alloantibody specific for Pl^A1 (HPA-1a) were unaffected by AP3 (lane 5). Essentially identical reactions were obtained with DDAbs 1 and 2 (not shown).