C3 and atypical hemolytic-uremic syndrome: The surface of the host cells is also protected from the action of C3 convertase, thanks to polyanionic molecules exposed on the membrane such as glycosaminoglycans, heparin and sialic acid, which by binding to FH facilitate its interaction with C3b, promoting its hydrolysis by FI (94) Mutations affecting the genes coding for regulatory proteins, present in heterozygosity (haploinsufficiency), predispose subjects to pathologies, such as atypical Hemolytic Uremic Syndrome (aHUS), type II Membranoproliferative Glomerulonephritis and Macular Degeneration related to age (95).