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. 2019 May 21;87(6):e00077-19. doi: 10.1128/IAI.00077-19

FIG 4.

FIG 4

Sialic acid-mediated decrease in IgM binding is required for decreased complement-mediated killing of NTHi. NTHi 11P6H bacteria were incubated with 10% HI-IgA/IgM-deficient serum (IgG/IgM) or 10% IgA/IgM-deficient serum (C3/C5b9) with or without IgM supplementation in HBSS3+ for 30 min, and surface binding of IgG (A), IgM (B), C3 (C), or C5b9 (D) was determined by flow cytometry (n = 4). (E and F) NTHi 11P6H (E) and NTHi 11P6HΔsiaP (F) bacteria were incubated with 5% IgA/IgM-deficient serum or 5% HI-IgA/IgM-deficient serum with or without IgM supplementation in HBSS3+ for 1 h, and survival was determined by dividing the CFU counts in IgA/IgM-deficient serum by the CFU counts in HI-IgA/IgM-deficient serum after 1 h of incubation (n = 4). A two-tailed paired t test was used for statistical analysis. *, P < 0.05; **, P < 0.01; ***, P < 0.001; NS, not significant.