Effects of thrombin, HLE, Cat G, and PR3 on the expression of the thrombin receptor at the surface of platelets. Unstirred platelets were incubated for 5 minutes with thrombin (A) or the neutrophil proteinases (B to D) as described in the legend to Fig 6. Binding of the IIaR-A antibody was measured by flow cytometry as detailed in the legend to Fig 5. For each experimental condition, the observed tracing (in black) is shown for comparison with a typical tracing (superimposed) representative of the control condition (ie, without pretreatment with any of the proteinases). The MFI value for the control irrelevant monoclonal IgG was 15.2 ± 2.1 (n = 10). Tracings are representative of at least three distinct experiments.