Immunohistochemical analysis of C3 and C9 (C5b-9) staining in kidney biopsy specimens from aHUS patients. Representative results are shown. (A) C3 deposits with main endothelial localization in a glomerulus from a patient with a CFI mutation and normal SC5b-9 plasma levels. (B) C9 staining restricted to hilar area in a glomerulus from a patient with a C3 mutation. (C) Diffuse C9 deposits in 2 glomeruli with marked ischemic injury from a patient with CFH mutation and increased SC5b-9 levels. (D) C9 deposits in glomeruli from a patient without mutations/anti-CFH antibodies. (E-F) endothelial C3 staining in arterioles from patients with CFH (E) and CFI (F) mutations. (G) Subendothelial localization of C9 staining in an arteriole from a patient with a CFH mutation and normal SC5b-9 level. (H) Control section (healthy portion of nephrectomy for cancer, C9 staining). Original magnification ×400, counterstaining with hematoxylin.