Association of CIB with GPIIb upon platelet adhesion to immobilized Fg. (A) Confocal images of washed platelets that were fixed at various stages of platelet spreading on Fg. Platelets were then stained for CIB (red) and GPIIb (green). The bottom row shows the merged images. Original magnification, × 1600. (B) Western blot analysis of CIB immunoprecipitates from detergent extracts of platelets plated on BSA or Fg. The majority of CIB interacts with GPIIb only after platelet adhesion to Fg. (C) Densitometric analysis of panel B, indicating that significant amounts of CIB and GPIIb/IIIa associate when platelets spread on Fg (P < .05). Error bars indicate mean ± sem of at least 3 independent experiments. (D) Western blot analysis of CIB immunoprecipitates from the RIPA buffer–solubilized Triton X-100–insoluble pellet of platelets plated on BSA or Fg. CIB and GPIIb/IIIa are associated with each other upon Fg binding, and this association is not disrupted upon translocation to the platelet cytoskeleton.