Ficolins are a group of multimeric lectins made up of single subunits each of which is composed of a collagen-like domain and a fibrinogen-like domain. Most of the ficolins identified to date bind to acetylated compounds such as N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc). Ficolins in serum are complexed with MBL-associated serine proteases (MASPs) and their truncated proteins. These lectins play an important role in innate immunity. Binding of the ficolin-MASP complex to carbohydrates present on the surface of microbes initiates complement activation via the lectin pathway.