May function in innate immunity through activation of the lectin complement pathway. Binds to GalNAc and GlcNAc carbohydrate moieties. Homotrimer. May form higher-order oligomers. Expressed in peripheral blood leukocytes. Also detected at lower levels in spleen and lung. The fibrinogen C-terminal domain mediates calcium-dependent binding to carbohydrates. The domain undergoes a conformational switch at pH under 6.2, and loses its carbohydrate-binding ability. N-glycosylated. Belongs to the ficolin lectin family.