FIG. 6.

SAP inhibits the LPS-mediated, antibody-independent, activation of the classical complement pathway. E. coli J5 was grown overnight in Mueller-Hinton broth, washed, and incubated in 3% SAP⁻/Ab⁻ serum in the absence of antibodies or in the presence of 3 and 30 μg of rabbit anti-E. coli J5 antibodies/ml with increasing concentrations of SAP for 30 min at 37°C. C3 deposition was determined via a subsequent incubation with FITC-labeled anti-C3c MAb. Data are MFI for three separate experiments ± SEM.