FIG 5.

Binding of serum IgG, CRP, and C3b to S. mutans strains in the presence of serum. (A and B) Strains were treated with 20% human serum, and levels of surface IgG (A) and CRP (B) were determined by flow cytometry (MFI). S. pneumoniae strains D39 and TIGR4 were used as controls for CRP binding. (C) Levels of C3b binding were measured after treatment of bacteria with reference serum, serum depleted of C1q (C1q−), or serum depleted of C1q and supplemented with purified C1q (C1q+). Columns represent means of results from three independent experiments; bars represent standard deviations. Strains were compared by using a Kruskal-Wallis test with Dunn's post hoc test. Asterisks indicate significant differences in relation to UA159 under the same conditions (P < 0.05).