Complement activation on necrotic endothelial cells. (A) Necrotic HUVECs (spontaneously detached during a 24-hour culture) were incubated with one-fourth diluted factor B–depleted human serum, reconstituted with recombinant WT or mutant factor B, and analyzed as in Figure 5A. The figure presents a typical flow cytometry histogram. The anti-C3c mean fluorescence intensity for the 2 mutations (n = 4 independent experiments) was significantly higher than the WT (t test, P < .05). (B) Levels of sC5b-9 in the serum after incubation with necrotic HUVECs. Results represent the mean ± SD of the results obtained from samples from 2 independent experiments tested in duplicate.