Human Ficolin is formed in the liver and secreted in the blood and is a major pattern recognition molecule in the serum plasma. It consists of collagen like tail linked to fibrinogen related globular head. Human ficolin has a complete set of complex binding site which is arranged in the internal cleft which enables the recognition of various molecular patterns. This kind of binding sites are not observed in other ficolins.  It is one amongst the few molecules which are known to activate the compliment lectin pathway. Human ficolins are three in number and present in the blood. M-Ficolin, L-ficolin and H-ficolin and are known as monocyte ficolin, liver ficolin and hakata antigen respectively. L and M-ficolin have similar amino acid sequences while H-ficolin has 50% similarity to the other two ficolins.

H-ficolin is defined and identified by autoantibodies which are present in lupus patients and is synthesized in lung and liver. L-ficolin insufficiency is usually associated with perinatal infection in preterm babies. Serum L-ficolin values are observed to be lower than normal in women who experience recurrent miscarriages. L-ficolin is increased by several folds during normal pregnancy and lower in preeclamptic pregnancies. L-ficolin is also important in various respiratory infections and it binds to respiratory pathogens and also opsonises them. Various pathogens include P. aeruginosa, S. aureus, S. pneumoniae, and H.influenzae. Insufficient levels of L-ficolin are associated with allergic rhinitis and asthma infections. A clear association of low L-ficolin levels in serum to idiopathic bronchiectasis is also known. There are many evidences which prove the basis of protection against P.aeruginosa colonization. People with low L-ficolin in serum are associated with diseases and experience poor quality of life.