TLR9 and infection: Treating SAOS-2 cells with the antioxidant DPI obviously reduced S. aureus killing ability of the TLR9 agonist, CpG-ODN2216, because survival of intracellular S. aureus has significantly increased 4 h and 20 h after infection in SAOS-2 cells pretreated with both ODN2216 and DPI in comparison to treatment with ODN2216 alone indicating that intracellular S. aureus was killed throughTLR9-mediated oxidative stress (Fig. 4).