FIG. 2.

The CCP (but not the ACP) is required for serum killing of the lptA::spc mutant. Serum bactericidal assays were performed using FA19, its lptA mutant (lptA::spc; labeled lptA), and the complemented lptA mutant (lptA::spc lptA⁺; labeled lptA⁺ Comp) using 20% (vol/vol) C1q-depleted (C1q⁻) NHS without CCP and MBL-deficient (A) or factor B-depleted (fB⁻) NHS that was ACP deficient (C). In control assays CCP activity was restored to C1q⁻ serum by the addition of purified C1q (final concentration of 100 μg/ml) (B), and ACP activity was restored to fB⁻ sera by the addition of fB (final concentration of 200 μg/ml) (D). Values represent the average percent survival calculated from three or more independently performed experiments. Where indicated, the assay was performed in the presence or absence of 1 mM IPTG.