Figure 5.

Degradation of C4b by C4bp bound to OmpA⁺Escherichia coli. (a)Either OmpA⁺ or OmpA^–E. coli grown to LP and PEP were incubated with NHS or purified C4bp for various periods at 37°. The bacteria were then collected by centrifugation, washed, and incubated with C4b and FI for 1 hr at 37°. The bacteria were then pelleted and a portion (30 μl) of the supernatant was dissolved in SDS buffer, and subjected to immunoblotting with anti-C4d antibody (recognizes α-chain of C4b and C4d). The experiments were carried out at least three times with similar results. (b)The bands of C4d on the blot were scanned, the intensities of the bands were normalized to number of bacteria loaded, and plotted on graphs.