Anti-FH.07 restores complement regulation in aHUS patient serum on E_S. (A) Schematic representation of the 20 CCP domains of FH with the location of the heterozygous mutations of each of the aHUS patients (numbered 1 to 11), as well as the domain targeted with anti-FH.07. (B) Incubation of E_S with serum from an aHUS patient carrying a heterozygous mutation in CFH (n = 2) or a serum pool from healthy individuals (NHS pool, n = 3). Hemolysis was measured at 412 nm and corrected for background at 690 nm. The hemolysis observed by incubation of E_S with 0.6% (wt/vol) saponin was set to 100%. (C) Addition of anti-FH.07 or an isotype control to 10% (vol/vol) serum of aHUS #1 or a NHS pool (n = 4). (D) Hemolysis observed in 11 aHUS sera (10%, vol/vol) with different CFH mutations before and after addition of anti-FH.07 or an isotype control; numbers correspond to the aHUS patient number in panel A. Addition of EDTA serves as the negative control of E_S lysis. Each point represents the mean of duplicates of a single experiment, and red lines indicate overall mean with standard deviation. (E) Comparison of the effect intact IgG and Fab′ fragments from a control IgG mAb and anti-FH.07 in the E_S hemolytic assay performed with 10% (vol/vol) aHUS#1 serum. Data in panels C-E are presented as mean with standard deviation. *P < .05, ****P < .0001, 2-way ANOVA.