May function in innate immunity through activation of the lectin complement pathway. Calcium-dependent and GlcNAc-binding lectin. Has affinity with GalNAc, GlcNAc, D-fucose, as mono/oligosaccharide and lipopolysaccharides from S.typhimurium and S.minnesota. Homotrimer (PubMed:17215869). May form an octadecamer consisting of an elementary trimer unit. Does not interact with fibronectin, elastin or zymosan. Interacts with MASP1 and MASP2. Found in blood plasma, bronchus, alveolus and bile duct. Liver and lung. In liver it is produced by bile duct epithelial cells and hepatocytes. In lung it is produced by both ciliated bronchial epithelial cells and type II alveolar epithelial cells. The N-terminus is blocked. The disease is caused by variants affecting the gene represented in this entry. Belongs to the ficolin lectin family.