Reactions of DDAbs 1 to 3 and monoclonal AP3 were lost when selected amino acids in GPIIIa were converted from human to the corresponding rat residue.

Reactions of the 3 DDAbs were abolished when amino acids 50, 62, or 66 were changed from the human to the corresponding rat residue, but similar modifications of amino acids 42, 63, 67, or 71 were without effect. Binding of monoclonal AP3 was abolished when only amino acids 50 or 62 were converted. None of the mutants were recognized by the DDAbs in the absence of quinine (not shown).