MV prepared and stained in phosphate

buffered saline or HEPES buffered saline (HBS; pH 7.4) without calcium served as negative controls for annexin-V. The absolute count of MV either in the absence or presence of single or dual staining was calculated with the relation: MV=GMVGTCTCVwhere GMV is the number of events in the MV gate, GTC is the number of events in the TruCOUNT™ bead gate, and TC is the number of TruCOUNT™ beads added to the sample of volume V (Shet et al., 2003 and Jayachandran et al., 2008). Except for comparison of instruments, the FACSCanto™ flow cytometer was used for all other measurements. find more Unless otherwise indicated data are shown as mean ± SD. PFP (5 μL) was diluted 1/20 with Hanks’/HEPES (pH7.4), and then 4 μL of fluorochrome-conjugated annexin-V and cell-specific

antibodies were added. These mixtures were briefly vortexed and incubated Belinostat mw in the dark for 25–30 min at room temperature. The mixture was diluted with 800 μL of Hanks’/HEPES or buffered saline solution (HBS; 20 mM HEPES, 150 mM NaCl, 2.5 mM calcium) and 100 μL of TruCOUNT™ beads. Side scatter events from size calibration beads of 0.2 μm, 0.5 μm, 1 μm and 2 μm were resolved from instrument noise with the 18-bit FACSCanto (105-channel) flow cytometer (Fig. 1). Inspection of the scatter plot (Fig. 1B) indicates that 0.2 μm is the lower limit for beads, which have a higher index of refraction, Wilson disease protein and therefore lower size threshold, than membrane vesicles (Koch et al., 1966, Foladori et al., 2008, Lacroix et al., 2010 and Yuana et al., 2011). More than 90% of MV isolated from plasma showed scatter intensities lower than that of 1 μm beads (Fig. 1C). Fluorescence events from anti-CD42a and annexin V from within the MV scatter gate accounted for more than 99% of events (Fig. 1C). For the sample shown in Fig. 1D, all but a small fraction (Q4) of counts were positive for both ligands, a finding typical for platelet MV (Jayachandran et al., 2008). MV counts were calculated from the nominal number of

beads added per volume of sample, with a minimum of 1000 TruCOUNT™ bead events (typically 2500) per analysis. The coefficient of variation of ten aliquots of 0.5, 1 and 2 μm beads was 7.2%, 2.6% and 2.4%, and MV counts calculated with the TruCOUNT™ internal standard were not significantly affected by flow rate. The choice of anticoagulant had a substantial impact on both platelet and endothelial MV counts (Fig. 2). Both platelet and endothelial MV were fewer in preparations from blood collected in calcium chelating anticoagulants versus protease inhibitors. When counts were above the 90th percentile, endothelial (CD62-E positive) MV were effectively eliminated (P < 0.003) in preparations from blood collected in sodium citrate compared to H&S.