Figure 3.

LTA from Staphylococcus aureus ΔdltABCD has a reduced ability to inhibit platelet aggregation. A, Washed human platelets (4 × 10⁸ cells/mL) were incubated for 15 minutes with LTA extracted from S. aureus strains SA113 or SA113 ΔdltABCD (4 µg/mL) followed by stimulation with CRP-XL (0.5 µg/mL). B, Platelets in PRP were preloaded with Fluo-4NW dye. Platelets were then pre-incubated with LTA extracted from S. aureus strains SA113 or SA113 ΔdltABCD (4 µg/mL) or Tyrodes buffer for 15 minutes followed by stimulation by CRP-XL (0.5 µg/mL). Intracellular mobilization of calcium was measured by spectrofluorimetry for 120 seconds. Ai, Representative aggregation traces of washed platelets. Aggregation was measured for 90 seconds. Ai, Representative aggregation trace. Aii, Data are plotted as percentage maximum fluorescence (vehicle treated representing 100% aggregation) and represent mean values ± SEM. Bi, Representative calcium flux trace. Bii, Data are plotted as percentage endpoint fluorescence (vehicle treated representing 100% aggregation) and represent mean values ± SEM. *<.01, **P < .005. Abbreviations: CRP-XL, cross-linked collagen-related peptide; LTA, lipoteichoic acid; SEM, standard error of the mean.