Figure 5.

Relative effects of α_IIbβ₃ clustering and affinity modulation on the binding of multivalent PAC1 IgM and monovalent PAC1 Fab to CHO cells. Cells stably expressing α_IIb(FKBP)₂β₃ were incubated with a saturating concentration of PAC1 IgM (40 nM) or recombinant PAC1 Fab (30 nM) for 30 min in the absence or presence of AP1510, and specific binding of PAC1 was quantitated by flow cytometry. Unlike most other experiments, PAC1 was expressed here simply as mean fluorescence intensity in arbitrary units since correction for the degree of integrin expression was not necessary. Data represent the means ± SD of triplicate values from one experiment representative of two so performed.