Genetic disruption of PIGA augments cell killing in aHUS serum. (A) Comparison of nonviable cells between TF-1 wild-type and TF-1 PIGA-null cells (data are presented as mean with SEM) after incubation with normal and aHUS serum. (B) Percentage of nonviable PIGA-null TF1 cells among different disease entities (data are presented as mean with SEM). Serum from aHUS patients induces significantly increased percentages of nonviable cells compared with healthy controls (P < .001), TTP (P < .001), and DIC (P = .001). Gray triangles symbolize values of aHUS patients treated with eculizumab, whereas black triangles symbolize aHUS in acute phase or remission. CVF, CVF-activated serum; Stec-HUS, Shiga-toxin–associated hemolytic uremic syndrome.