FIGURE 2.

C3a generation by Cap+ and Cap− isogenic meningococcal mutants. Five Cap+ and Cap− isogenic mutant pairs of meningococcal strains (one representative of each meningococcal serogroup) that lacked LOS sialic acid, fHbp, and NspA were incubated with C2-depleted human serum (final concentration 25% (v/v)). Aliquots were collected at 10 and 30 min and C3a generated in the reaction mixture was measured by ELISA. Baseline levels of C3a generation were measured in control reaction mixtures that contained C2-depleted serum in HBSS²⁺ (no bacteria added) and is shown by the bar labeled C2-dep. Each data point represents the mean ± S.D. of 3 separate experiments.