Anti-FH.07 increases complement regulation on human cell surfaces. (A) Immunofluorescent imaging of C3b deposition on HUVECs incubated with 10% (vol/vol) NHS, HI-NHS, or aHUS-like NHS in the absence or presence of anti-FH.07. For each condition, a representative image of independent experiments (n = 3) is shown. (B) Relative C3b deposition on HUVECs (from panel A), calculated by quantifying the mean fluorescence intensity (MFI) using a maximum intensity projection of the whole coverslip (10 × 10 × 15 images per coverslip). Anti-C3.19 MFI of NHS was set to 1. Bars represent mean with standard deviation (n = 3). (C) Immunofluorescent imaging of C3b deposition on HUVECs following incubation with 10% (vol/vol) serum of 5 aHUS patients in the absence of presence of an isotype control mAb or anti-FH.07. In panels A,C, HUVECs were stained with Hoechst (turquoise, nuclei), WGA (magenta, plasma membrane), and anti-C3.19 (green, C3b deposition). Scale bars in panels A,C represent 100 µm. *P < .05, 1-way ANOVA.