Figure 1. Nucleotide-binding oligomerization domain (Nod2)^−/− mice exhibit attenuated cecal ligation and puncture (CLP)-induced sepsis through suppression of C5a generation.

To induce sepsis, the cecum of wild-type (WT) or Nod2^−/− mice was ligated and punctured. (A) Serum and peritoneal C5a and C3a levels were evaluated in WT and Nod2^−/− mice 24 h after CLP (n = 4). (B) The percentages of surviving mice were estimated during CLP-induced sepsis (^aP = 0.951[not significant], ^bP = 0.0077, ^cP = 0.0141, log-rank test; WT [n = 12], WT mice injected with recombinant C5a [n = 8], Nod2^−/− [n = 8], Nod2^−/− mice injected with recombinant C5a [ n = 8]) (C) Peritoneal cells obtained from WT (n = 4), Nod2^−/− (n = 4), or Nod2^−/− mice injected with recombinant C5a (n = 6) 4 and 12 h after CLP were incubated with LPS or PBS for 6 h and cytokine levels were measured. The responsiveness of peritoneal cells to LPS was determined by estimating the ratios of individual cytokines produced in response to LPS versus PBS. (D) Serum D-dimer levels were measured in WT (n = 5), Nod2^−/−(n = 5), Nod2^−/− mice injected with recombinant C5a (n = 4) 24 h after CLP. (E) Phagocytosis activity of peritoneal cells obtained from mice 24 h after CLP was determined by measuring the percentage of cells with intracellular FITC-conjugated E. coli after 15 min incubation. (n = 3) (F) Bacterial CFUs were counted using blood and liver homogenates obtained from mice 24 h after CLP. (n = 3) *P<0.05, **P<0.01, ***P<0.001 (two-tailed unpaired t-test [a, c–f]) for WT B6 vs. Nod2^−/− mice and Nod2^−/− vs. Nod2^−/− mice injected with recombinant C5a. Results shown are representative of three independent experiments except for (B) (mean and SEM).