Figure 2.

The inhibition is due to the presence of Staphylococcus aureus LTA. A, Washed human platelets (4 × 10⁸ cells/mL) were preincubated with anti-LTA antibody (1 µg/mL) before incubation for 15 minutes with LTA (2 µg/mL) followed by stimulation with CRP-XL (0.5 µg/mL). Aggregation was measured as change in light transmission for 90 seconds. NB: In Ai, lines representing platelets treated with 2 µg/mL + anti-LTA antibodies and untreated platelets, overlap extensively. B, Washed platelets were incubated for 15 minutes with LTA extracted from S. aureus SA113 (4 µg/mL), Bacillus subtilis, or Streptococcus pnuemoniae D34 (12.5 µg/mL) followed by stimulation with CRP-XL (0.5 µg/mL). C, Washed platelets were incubated for 15 minutes with LTA extracted from B. subtilis at a range of concentrations followed by stimulation with CRP-XL (0.5 µg/mL). D, Washed platelets were incubated for 15 minutes with supernatant from S. aureus SEJ1, SEJ1 ΔgdpP, SEJ1 ΔltaS ΔgdpP or SEJ1 ΔltaS ΔgdpP pCN34-ltaS (10 µg/mL), followed by stimulation with CRP-XL (0.5 µg/mL). (Ai, Bi, Di) Representative aggregation traces of washed platelets. Aggregation was measured for 90 seconds. (Aii, Bii, C, Dii) Data are plotted as percentage inhibition of aggregation represent mean values ± SEM. *P < .05, **P < .001. Abbreviations: CRP-XL, cross-linked collagen-related peptide; LTA, lipoteichoic acid; SEM, standard error of the mean.