Functional defects in WIP KO platelets. WT, WASp KO, WIP KO^low, and WIP KO^high platelets were activated with increasing concentrations of CRP or thrombin for 2 minutes at 37°C, as indicated. Platelets were then incubated with an FITC-labeled anti–mouse P-selectin antibody or with Oregon Green 488–labeled fibrinogen, and analyzed by flow cytometry. Results are percentage of positive platelets compared with rest and represent the mean ± SE of 4 independent experiments. Resting and activated platelets were fixed, permeabilized, stained with TRITC-labeled phalloidin, and analyzed by flow cytometry. Results are the ratio between the fluorescence of activated versus resting platelets and represent the mean ± SE of 3 independent experiments.