Effects of blocking FH and MCP on the regulation of C3 deposition from WT or R139W sera. (A) GEnCs preactivated with TNFα/IFNγ were incubated for 30 minutes with the standard normal human serum, FHdpl, or R139W sera, in the presence or absence of blocking mAbs against FH (Ox24) or MCP (GB24). The C3 deposition was evaluated by flow cytometry as in Figure 2A. ***P < .0001, unpaired t test. Unless specifically mentioned, the comparison was made with the NHS (the first bar with a black and white pattern). (B) GEnCs activated with TNFα/IFNγ were incubated for 30 minutes with normal human sera, FHdpl, or R139W sera in the presence of increasing doses of purified FH. C3 deposition in the absence of FH for the FHdpl or R139W-positive sera (from aHUS patient and healthy carriers) was taken as 100% and each C3 level percentage, in the presence of different doses of FH, was calculated. The starting FH concentration was in the normal range for P5, 5.F, and 5.S1. The level of C3 deposition from a normal serum is given as a straight line.