Quinine-dependent reactions of mAb 314.1 with CHO cells expressing human/rat chimeric or wild-type human GPIIb paired with human GPIIIa. (A) mAb 314.1 reacted with wild-type GPIIb (H, solid histogram) and with a GPIIb containing human sequence in the N-terminal β propeller domain (H_1-452R, dotted histogram) but not with the inverse construct containing rat sequence in the β propeller domain (R_1-452H, dashed histogram). (B) mAb 314.1 binding was lost when the first 2 (R_1-144H, dotted histogram) or 3 (R_1-246H, dashed histogram) N-terminal repeats (blades) of the human β propeller domain were replaced by a rat sequence. All reactions contained quinine 0.4 mM. There were no significant reactions in the absence of quinine (not shown). (C,D) Reactions of mAb AP2 (specific for the GPIIb/IIIa complex) with the same CHO cell lines showed that all constructs were satisfactorily expressed.