LOS- and LPS-induced complement activation in vivo and in vitro. ELISAs of plasma C3 activation products in wild-type (WT) and properdin^−/− mice 1 hour after LOS (A) or LPS (B) treatment. LOS or LPS was given at 20 mg/kg (intraperitoneally) and phosphate-buffered saline was used as a vehicle control. N = 3 mice per group. Error bars represent standard deviations. A wild-type mouse plasma sample treated with CVF in vitro was used as a reference for C3 activation (100%). ELISA of LOS– (C) or LPS–induced (D) total complement activation in wild-type (WT), properdin^−/−, or factor B knockout (fB^−/−) mouse serum in GVB²⁺ buffer.