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. 2020 Sep 2;11:2122. doi: 10.3389/fimmu.2020.02122

FIGURE 2.

FIGURE 2

FH6-7/IgG competes out serum FH, but C4BP1-2/IgM does not compete out serum C4BP. (A) M. catarrhalis were pre-incubated in increasing amounts of FH6-7/IgG, followed by the addition of OmCI-treated serum (C5-inhibitor). The binding of FH from NHS was assessed by flow cytometry using antibodies specific to domains present in serum derived FH but absent on the fusion proteins. (B) FH6-7/IgG and NHS were added simultaneously to the bacteria and binding of FH from NHS was assessed. (C) M. catarrhalis pre-incubated in increasing amounts of C4BP1-2/IgM, followed by OmCI-treated serum were tested for the binding of C4BP from NHS by flow cytometry using antibodies specific to domains present in serum derived C4BP but absent on the fusion proteins. (D) Alexa Fluor 488-labeled C4BP-IgM was added simultaneously with differing concentrations of OmCI-treated serum to bacteria to assess the binding of the fusion protein. Mean (±SD) from three independent experiments are shown. Statistical significance of differences was calculated using one-way ANOVA with Dunnett’s post-test; ***p < 0.001 and ****p < 0.0001.