Platelet aggregation, secretion, and αIIbβ3 activation induced by ADP or thrombin are impaired in both patients. (A-C) Aggregation of washed platelets was initiated by various concentrations of ADP (10 and 20 μM) and thrombin (25 and 50 mU/mL) for 3 minutes. Aggregation was expressed as the percentage change in light transmission, with the value of the blank (buffer without platelets) set at 100%. Tracings are representative of at least 2 experiments per patient. (B-D) Quantification of activated αIIbβ3 at the surface of washed platelets was assessed by flow cytometry by binding of the specific monoclonal antibody (mAb) PAC1 to control and P1 and P2 platelets upon activation with ADP (5 and 10 μM) and thrombin (50 and 100 mU/mL). (E-F) Quantification of P-selectin exposure was assessed by flow cytometry using anti-P-selectin antibody and dense granule release with an ATP determination kit, respectively, to control and P1 platelets upon activation by thrombin (50 and 100 mU/mL). Results are representative of 2 experiments for each patient.