FIG 3.

Uptake of sialic acid decreases binding of CRP, IgG, and IgM to multiple NTHi bacteria. (A) NTHi 11P6H bacteria were incubated with 5% C1q-depleted serum or 5% HI-C1q-depleted serum with or without C1q supplementation in HBSS3+ for 1 h, and survival was determined by dividing the CFU counts in C1q-depleted serum by the CFU count in HI-C1q-depleted serum after 1 h of incubation (n = 4). Bacteria were incubated with 10% HI serum in HBSS3+ for 30 min, and surface binding of CRP (B), IgG (C), and IgM (D) was determined by flow cytometry (n = 4). A two-tailed paired t test was used for statistical analysis. *, P < 0.05; **, P < 0.01; NS, not significant.