FcγRII binding is required for PGN-induced integrin αIIbβ3 upregulation but not PS exposure. Platelet-rich plasma was stimulated with PGN (10 μg/mL) or anti-CD9 (10 μg/mL) at 37°C for 30 minutes. After fixation, platelets were permeabilized with saponin and stained with anti-phosphotyrosine antibody in the (A) absence or (B) presence of 10 mM free phosphotyrosine. (C-H) Flow cytometry analysis of PAC-1 staining (C-E) and annexin V staining (F-H) using washed platelets suspended in Tyrode buffer. Platelets were stimulated with nothing (no stimulation) or PGN preincubated with plasma for 30 minutes at 37°C (PGN + Plasma). Stimulation was done in the presence or absence of anti-human FcγRII blocking Abs (IV.3). (I) Quantitative and statistical data of 3 similar experiments. *P < .05; NS, not significant.
