Effect of complement on LPS-induced cytokine production in vivo. (A) ELISA assays of activated C3 products in plasmas of wild-type (WT) and DAF^−/− mice at various time points after LPS treatment. Percentage of C3 activation was relative to that of a mouse plasma sample activated in vitro by CVF. (B) ELISA assays of plasma IL-6 and IL-12p40 levels in WT, DAF^−/−, C3^−/−, and DAF^−/−/C3^−/− mice 3 hours after LPS challenge. (C) ELISA assays of plasma IL-6 and IL-12p40 levels in WT mice 3 hours after CVF, LPS, or CVF/LPS treatment. (D) Effect of a C3a receptor antagonist (C3aRa) and a C5a receptor antagonist (C5aRa) on LPS-induced plasma IL-6 levels in DAF^−/− mice. Polyethylene glycol 400 (PEG) was used as a vehicle control. Antagonists were administered 30 minutes before LPS injection. (E) ELISA assays of plasma IL-6 and IL-12p40 levels in WT, C3aR^−/−, and C5aR^−/− mice 3 hours after LPS or LPS/CVF treatment. N = 4-6 mice per group for panels A-E. Values shown are mean (± SEM); *P < .05, **P < .01, Student t test.