Binding of CHO cells, transiently transfected with α_IIb plus either normal or deleted β₃ mutants, to fibrinogen or PAC-1. (A) The surface expression of α_IIbβ₃ complexes was determined by flow cytometry using a mAb directed against α_IIb, as described in “Materials and methods.” (B-C) Transfected CHO cells were incubated with FITC-PAC-1 (B) and FITC-Fg (C) as described in “Materials and methods.” Nonspecific fibrinogen binding was determined in the presence of 10 mM EDTA (▦). Data are expressed in arbitrary units. The values are means ± SEMs of 4 independent experiments performed in duplicate.