Fig 3.

Deposition of human C4b and C3b on live bacterial cells of group B strain H44/76 as measured by flow cytometry. The bacteria were incubated with human complement and 4 μg of chimeric anti-fHbp MAbs/ml. IgG1, black solid lines; IgG2, gray solid lines; and IgG3, black dashed lines. An irrelevant human MAb (4 μg/ml) was used as a negative control (gray filled histograms). (A) Activation of C4b deposition using 10% commercial C6-depleted human serum, which also had been depleted of IgG as described in Materials and Methods. (B) Activation of C3b deposition. The MAb concentrations and complement were the same as those for panel A. Similar respective results were obtained in two independent experiments with C6-depleted human serum as the complement source and in a third experiment with a different human complement source that had not been C6-depleted (data not shown).