Flow cytometric analysis of binding of CHO cells expressing either normal or mutated β₃ receptors to FITC-labeled fibrinogen. CHO cells stably expressing heterodimers of normal or mutant β₃(616-690del) with endogenous α_v or with transfected α_IIb were incubated with soluble FITC-fibrinogen alone or in the presence of mAbs directed against activated α_vβ₃ (WOW-1) or activated α_IIbβ₃ (PAC-1), 2 mM MnCl₂,or 5mM EDTA. Bound fluorescence was determined by flow cytometric analysis.