Flow cytometry.

The suspension cell line Daudi (upper panel) or Raji (lower panel) was incubated 18 hours with either 0 (open squares) or 1000 IU/mL (closed circles) IFN-α2a and then analyzed for cell surface–exposed phosphatidylserine, as detected by the binding of coagulation factor Va (FVa; see “Materials and methods”). Ordinate represents percent of cells analyzed by flow cytometry detected as positive for bound FVa. Error bars represent mean and range of combined results of 2 independent experiments. Similar data were obtained for Jurkat cells (not shown).