FIG. 4.

The expression of PrtF1/SfbI partially decreases C3d deposition on the surface of 90-226 M1⁻. In strain 90-226 M1⁻ pKH3 (A), 80% of the bacteria fix C3d on their surfaces, compared to 50% of the strain 90-226 M1⁻ F1⁺ population (B). The 90-226 strains were incubated with human heparinized plasma, and C3d deposition was quantitated by flow cytometry. Gray line, isotype control antibody; black line, mouse anti-human C3d antibody. Representative data from two experiments are shown. FITC, fluorescein isothiocyanate.