Effect of mutations on the ability of FH19-20 in preventing FH-mediated protection of erythrocytes from complement-mediated lysis in serum. (A) Es were incubated in EGTA-containing NHS (15%) in the presence of increasing concentrations of wt or mutant FH19-20. (B) Eh were incubated with wt or mutant FH19-20 (20 µM) in 33% NHS with EGTA. (A-B) Hemolysis in each sample was determined by measuring the absorbance of the supernatant at 414 nm compared with that obtained with total lysis performed with water. The assays were performed (A) 6 or (B) 3 times. Shown are average values ± standard deviation (SD). One-way analysis of variance (ANOVA) with Tukey’s multiple comparison posttests was performed. ***P < .001.