Complement factor I, Human, Natural

Complement Factor I (fI) is a protein of the complement system, first isolated in guinea pig serum that regulates complement activation by cleaving cell-bound or fluid phase C3b and C4b.
Factor I deficiency in turn leads to low levels of complement component 3 (C3) in plasma, due to unregulated activation of the complement alternative pathway, and it has been associated with recurrent bacterial infections in children; more recently, mutations in the Factor I gene have been shown to be implicated in development of Haemolytic Uremic Syndrome, a renal disease also caused by unregulated complement activation.