Mutations in the plasma complement regulator factor H (CFH) and the transmembrane
complement regulator membrane co-factor protein (MCP) have been shown to predispose to
atypical hemolytic uremic syndrome (HUS). Both of these proteins act as co-factors for
complement factor I (IF). IF is a highly specific serine protease that cleaves the α-chains of
C3b and C4b and thus downregulates activation of both the classical and the alternative
complement pathways. This study looked for IF mutations in a panel of 76 patients with HUS …