The present invention relates to substantially pure mannan-binding lectin associated serine protease-2 (MASP-2) polypeptides and fragments thereof as well as nucleic acids encoding such polpeptides. Furthermore, the present invention relates to uses of a substantially pure polypeptide comprising amino acid sequences derived from mannan-binding lectin associated serine protease-2 (MASP2) or a functional homologue thereof for the production of a pharmaceutical composition as well as pharmaceutical compositions comprising MASP-2 and/or MASP-2 fragments. In addition the present invention relates to inhibitors of MASP-2 and pharmaceutical compositions comparing such inhibitors. Methods for detecting MASP-2 nucleic acid expression are included in the invention.