Figure 4.

C3b deposition by antiserum to factor H binding protein (fHbp) ID 1 or 55 with fH-depleted or fH-repleted human complement. A, fHbp ID 1 mutant strain incubated with mouse antisera and fH-depleted human serum. Antiserum to fHbp ID 1 is denoted by the solid black line, antiserum to fHbp ID 55 is denoted by the dashed black line, and negative control antiserum (adjuvant alone) is denoted by the dotted grey line. B, ID 55 mutant strain incubated with mouse antisera and fH-depleted complement. Line patterns are the same as in A. C, ID 1 mutant strain incubated with mouse antisera and fH-repleted complement (addition of 50 µg/mL purified human fH). D, ID 55 mutant strain incubated with mouse antisera and fH-repleted complement. Experiments used 5% fH-depleted, pooled human serum that also had been depleted of immunoglobulin G as the source of complement (see Materials and Methods).