FIGURE 5.

iC3b is deposited on group W-135 and Y capsular polysaccharides. A, Western blotting to detect capsular polysaccharide on Cap+ strains. The five Cap+ strains that were incubated with 25% (v/v) Mg/EGTA-NHS were Western blotted and probed with a mAb against the respective capsular polysaccharide. No reactivity was seen in control blots (anti-capsular mAb excluded; data not shown). B, iC3b is deposited selectively on group W-135 and Y capsular polysaccharides. The Cap+ mutant strains were incubated with 25% (v/v) Mg/EGTA-treated serum for 30 min. Bacteria incubated with heat-inactivated normal human serum (HI-NHS) served as negative controls. Following washing of bacteria, the pellets were treated with DNase I to decrease sample viscosity. Western blotting for iC3b detection and Coomassie staining to confirm similar loading across strains was performed as described in the legends to Figs. 3 and 4.