Systemic blockade of both TLR4 and TLR2 upon S. enterica or E. coli challenge inhibits cytokine release, enhances pathology if an infection is not followed by antibiotic therapy, and protects from septic shock if synchronized with the start of antibiotic therapy. (A–C) Mice received 1A6 and T2.5 mAb (⋄; n = 6) or isotype control mAb (▴; n = 6) 1 h before i.p. challenge with 5 × 10⁷ CFU E. coli that had been pretreated with antibiotics in vitro immediately before injection (▪, TLR2^−/−/TLR4^−/− mice, used as positive control; n = 3). Serum samples drawn as indicated were subjected to ELISA. Each experimental group was analyzed in the course of three individual experiments. (D) Wild-type mice received mAbs (i.c., isotype control; T2.5, anti-TLR2; 1A6, anti-TLR4) 1 h before infection with 10⁶ CFU S. enterica (ent.) by i.p. injection. 24 h later, mice were killed and bacterial loads of compartments indicated were determined (n = 6 for each experimental group). (E–J) Wild-type mice received mAb (⋄, isotype control; •, 1A6; ▿, T2.5; ▴, 1A6 and T2.5; *, P < 0.004 for comparison to specific dual TLR blockade groups): 1 h before infection with 10⁸ CFU S. enterica to be left untreated thereafter (E; n = 7 per group split for three independent experiments), 1 h before infection with 5 × 10⁹ CFU E. coli and 2 h before antibiotic therapy (F; n = 5 per group split for two independent experiments), at the start of antibiotic therapy 1 h after infection with 5 × 10⁹ CFU E. coli or 10⁹ CFU S. enterica (G and H; two individual experiments with n = 5 per group), or (results of three individual experiments) at the start of antibiotic therapy 4 h after infection with 5 × 10⁸ CFU E. coli (n = 9 for ▴, n = 10 for ⋄) or 10⁸ CFU S. enterica (n = 10 for both experimental groups; I and J).