The invention relates to polypeptides, and in particular to polypeptides that are capable of inhibiting the activity or activation of the complement system. It also relates to nucleic acids that encode the polypeptides and to uses of the polypeptides.The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It forms part of the innate immune system. Down-regulation of complement activation has been demonstrated to be effective in treating several disease indications in animal models and in ex vivo studies. The present invention provides novel polypeptides that can be used for the treatment of diseases or disorders that relate to inappropriate activation of one or more of the complement pathways.
