The complement factor I is responsible for cleaving the alpha-chains of C4b and C3b in the presence of the cofactors C4-binding protein and factor H respectively. These protein cleavages inactivate complement components C3Bovine, iC3b and C4b. Factor I consists of a heterodimer of a light and heavy chains linked by disulfide bonds. Factor I deficiencies (CFI) result in increasing risks for pyrogenic infections, such as hemolytic uraemic syndrome (HUS), an acute renal failure in childhood due to E. coli infection. This antibody recognizes human complement factor I in ELISA.