Fibrinogen binding and P-selectin expression are normal in diYF platelets. (A-B) Flow cytometry analysis of fibrinogen binding (A) and P-selectin expression (B) in WT and diYF platelets. Platelets were stimulated with the indicated concentrations of the PAR-4 agonist AYPGKF. Data are expressed as the percentage of positive cells (mean ± SEM, n = 3). (C-D) Representative photomicrographs from WT and diYF platelets showing GPIb (red) and P-selectin (green) expression by immunofluorescence. Platelets were stimulated with 100-µm AYPGKF and allowed to spread on immobilized fibrinogen for 45 minutes at 37°C. The cells were fixed and stained with anti-GPIb and anti-P-selectin without permeabilization to assess surface protein expression.