Mannose-binding lectin in human health and disease

Mannose-binding lectin (MBL) plays, as a soluble pattern recognition molecule, a central role in the innate immune response. MBL binds to the surface of carbohydrates on a wide variety of pathogens and mediates opsonophagocytosis via activation of the lectin complement pathway or by directly promoting opsonophagocytosis in a complement-independent manner, it has been reported that MBL acts as an immunomodulator and promoter of apoptosis. Additionally, MBL and the MBL-associated serine proteases-1 and -2 have been associated with the coagulation system. Therefore, it is not surprising that MBL deficiency has been associated with increased susceptibility to various infectious and autoimmune diseases. As a key component of the innate immune system, MBL is particularly important when the adaptive immune response is either immunocompromised or immunosuppressed; consequently, the majority of the reported cases of MBL deficiency associated with disease are found in infants or young children and immunocompromised patients. In this chapter, we will give a comprehensive overview of the literature on MBL by discussing its structure, function, interaction with its serine proteases, genetics and its role in association with various pathologies.