Ficolins are a group of proteins containing both a collagen-like domain and a fibrinogen-like domain. They are found in various tissues. The domain organizations between ficolins and mannose binding lectin (MBL) are similar, although the carbohydrate-binding moieties are different. In man two types of ficolins (Lficolin/ P35 and H-ficolin) are present in serum and one type (M-ficolin) in cells. L-ficolin/P35 (also L-ficolin, ficolin L, EBP-37 or hucolin) is produced primarily by the liver. The association between L-ficolin/P35 and MASPs/sMAP is Ca 2+ -dependent. MASPs in L-ficolin/P35-MASP complexes have proteolytic activities for C4, C2 and C3. L-ficolin/P35 also shows opsonic activity.