Binding of FMC25 and SZ1 to GPIX chimeras. The WT GPIX and the 4 human/mouse chimeras were expressed on the surface of CHOαβ cells, and the binding of anti-GPIX moAbs FMC25 and SZ1 was examined. An isotype-matched IgG was used as the negative control (gray solid histogram). Open histograms (black) depict the binding of FMC25 and SZ1 to CHOαβ cells expressing WT GPIX, chimeras 1, 2, 3, and 4.