Fibrinogen binding to platelets assayed by flow cytometry.

(A) Background fluorescence of unstimulated platelets incubated with the FITC-conjugated anti-insulin control antibody. The line above the x-axis was placed at approximately the point where the fluorescence curve terminated, and the number shows mean fluorescence intensity above the background. (B) Unstimulated platelets incubated with FITC-conjugated antifibrinogen antibody. (C) Fibrinogen binding to platelets stimulated with 100 pg/mL Stx1 (3% of cells were positive in this experiment; range, 3%-10% in 6 experiments). (D) Fibrinogen binding to platelets was reduced by preincubation of 100 pg/mL Stx1 (final concentration; see “Patients, materials, and methods”) with anti-Stx1.