Flow cytometric analysis of CHO-GPIIIa cells stably transfected with cDNAs encoding normal or mutant [intron 5]GPIIb. CHO cells derived from hygromycin-resistant clones were analyzed for surface expression of GPIIb-IIIa by flow cytometry. The cells were incubated with either anti-GPIIb (M3) or anti-GPIIIa (P37) MoAbs and then treated with FITC-conjugated rabbit F(ab′) antimouse IgG. (A) Surface expression of GPIIIa and GPIIb in cells inherently expressing human recombinant GPIIIa (CHO-GPIIIa cells). (B) Surface expression of GPIIb and GPIIIa in CHO-GPIIIa cells stably transfected with cDNA encoding normal human GPIIb. (C) Surface expression of GPIIb and GPIIIa in CHO-GPIIIa cells stably transfected with cDNA encoding [intron 5]GPIIb. NC, negative control, fluorescence of cells incubated only with the second antibody.