May function in innate immunity through activation of the lectin complement pathway. Calcium-dependent and GlcNAc-binding lectin. Enhances phagocytosis of S.typhimurium by neutrophils, suggesting an opsonic effect via the collagen region. Homotrimer (PubMed:17215869). Interacts with elastin. Interacts with MASP1 and MASP2. Interacts with CR1. Expressed by the liver and secreted in plasma. The fibrinogen-like domain (FBG) contains calcium-binding sites that may be involved in carbohydrate binding. Belongs to the ficolin lectin family.