Figure 3.

Effects of extracellular calcium and the GPIb-IX and GPIIb-IIIa complexes on TR_1–41-induced platelet activation. Diluted whole blood from normal volunteers was incubated (22°C, 10 min) with TR_1–41, TR_42–55, concomitant TR_1–41 and TR_42–55, or thrombin at the indicated concentrations in the presence of buffer alone (control), 2 mM EDTA, or 2 mM EGTA. Also, diluted whole blood from a patient with either Bernard–Soulier syndrome or Glanzmann’s thrombasthenia was incubated (22°C, 10 min) with TR_1–41 or thrombin at the indicated concentrations. The platelet surface binding of the P-selectin-specific mAb S12 was determined by flow cytometry. Binding is expressed as a percent of the binding with maximal thrombin (2 units/ml). Data are mean ± SEM. n = 6 except for data for Bernard–Soulier syndrome and Glanzmann’s thrombasthenia, which are means of two experiments.