Figure 5.

IgM cleavage by Ide_Ssuis reduces surface bound F(ab‘)2 and Fc antigen of porcine IgM. S. suis strain 10 (wt), 10∆ide_Ssuis (∆ide_Ssuis), 10∆ide_Ssuis∇ide_Ssuis_EcoRI (∇ide_Ssuis_EcoRI), 10∆ide_Ssuis∇ide_Ssuis_C195S (∇ide_Ssuis_C195S) were incubated in a porcine anti-S. suis serotype 2 hyperimmune serum for 0.5 hours at 4°C and then for four hours at 37°C. Bacteria were stained with IgM F(ab‘)2 and IgM Fc specific antibodies and measured by flow cytometry (n = 7) before and after incubation at 37°C. (a) Reduction of the percentage of IgM Fc positive bacteria. (b) Reduction of the geometric mean fluorescence intensity (MFI) of the IgM Fc signal. (c) Reduction of the percentage of IgM F(ab‘)2 positive bacteria. (d) Reduction of the geometric mean fluorescence intensity (MFI) of the IgM F(ab‘)2 signal. The reduction in IgM labeling was calculated by subtracting the percental amount or MFI of IgM positive bacteria after a four-hour incubation period at 37°C from an initially one hundred percent positive population before incubation at 37°C. Bars and error bars indicate mean and standard deviation. Asterisks indicate significant differences. Probabilities were considered as follows p < 0.05 *, p < 0.01 **, p < 0.001 ***.