Figure 6.

CR2-FH prevented triggered C3 accumulation on the GBM. Mice with combined deficiency of FH and FI (Cfh^−/−.Cfi^−/−) were treated with CR2-FH or PBS and 1 hour later either did (+) or did not (–) receive an injection of serum deficient in both C3 and FH (as a source of FI) to trigger GBM C3 deposition. Animals were culled 24 hours later and (A) plasma C3, (B) plasma C5, and (C,D) glomerular C3, and (C) CR2-FH assessed. (A) The C3 alpha prime chain of C3b was present in the Cfh^−/−.Cfi^−/− mice irrespective of prior treatment with CR2-FH or PBS. C3 alpha chain fragments were detected in all mice that received C3- and FH-deficient mouse serum irrespective of pretreatment with CR2-FH or PBS. (B) C5 became detectable in animals that had received CR2-FH irrespective of subsequent injection with C3- and FH-deficient serum. (C) Representative images of glomerular C3 (green) and CR2-FH (red), original magnification ×40, and (D) quantitative glomerular C3 immunofluorescence, horizontal bars denote median values. *P<0.001, Bonferroni’s Multiple Comparison Test. NS, not significant. GBM C3 reactivity was detected in mice injected with C3- and FH-deficient serum alone, but not in those who had been pretreated with CR2-FH with consequent significant reduction in glomerular C3 staining intensity. The intensity of the mesangial C3 staining pattern seen in mice that had not received C3- and FH-deficient serum was not altered by pretreatment with CR2-FH.