Abstract: The present invention relates to the identification of novel regulators of the innate immune system, in particular the complement system. More particularly, the present invention relates to specific C5 convertase inhibitors. These novel inhibitors are particularly useful for treating inflammatory diseases involving the complement system. In a first aspect, the present invention focuses on the use of CFHR proteins and functional fragments or functional derivatives thereof for preventing inflammatory reactions. In a further aspect, the present invention focuses on the use of said CFHR proteins for inactivating complement activation during transplantation and dialysis and for coating devices which come into contact with blood or body fluids, in particular implants. The invention furthermore provides a pharmaceutical composition comprising functional CFHR protein in combination with functional factor H.