Figure 1.

LTA from Staphylococcus aureus inhibits platelet aggregation. Washed human platelets (4 × 10⁸ cells/mL) or PRP were preincubated with LTA or tyrodes buffer and stimulated with various platelet agonists. Aggregation was measured as change in light transmission. Ai–Di, Representative aggregation traces of platelets incubated with LTA and stimulated with various platelet agonists. All aggregation traces commence upon addition of agonist. Aii–Dii, Data are plotted as percentage inhibition of aggregation or percentage aggregation (vehicle treated representing 100% aggregation) and represent mean values ± SEM. A, Platelets were pre-incubated with LTA at a range of concentrations followed by stimulation with CRP-XL (0.5 µg/mL). Aggregation was measured for 90 seconds. B, Platelets were preincubated with LTA at a range of concentrations followed by stimulation with Paf (37.5 µg/mL). Aggregation was measured for 90 seconds. C, Platelets were pre-incubated with LTA at a range of concentrations followed by stimulation with thrombin (0.05 units/mL). Aggregation was measured for 90 seconds. D, Platelets were preincubated with LTA (4 µg/mL) for 8, 10, 12, 14, and 16 minutes followed by stimulation with CRP-XL (0.5 µg/mL). Aggregation was measured for 90 seconds. E, PRP was pre-incubated with various concentrations of LTA for 15 minutes followed by stimulation with whole S. aureus SA113 cells (2 × 10⁸ cells/mL). Aggregation was measured for up to 20 minutes. Data are plotted as increase in lag time and represent mean values ± SEM. *P < .05 Abbreviations: CRP-XL, cross-linked collagen-related peptide; LTA, lipoteichoic acid; PRP, platelet-rich plasma; SEM, standard error of the mean.