MBL

MBL or Mannose-binding lectin is a protein that plays a crucial role in the immune system. It is a form of collectin that is found in the blood plasma and is associated with the innate immune system. MBL recognizes carbohydrates on the surface of many pathogens, including bacteria, viruses, and fungi, and activates the complement system via the lectin pathway.

Structure

MBL is a complex protein composed of smaller subunits. Each subunit consists of a polypeptide chain with a collagen-like region at the N-terminal end and a C-type lectin domain at the C-terminal end. The subunits assemble into higher-order structures, typically dimers, trimers, and tetramers, which are then further assembled into the functional MBL protein.

Function

The primary function of MBL is to bind to specific sugar moieties found on the surface of many pathogens. This binding can lead to opsonization of the pathogen, enhancing phagocytosis, or it can activate the complement system via the lectin pathway. The complement system is a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane.

Clinical significance

Deficiencies in MBL can lead to an increased susceptibility to infection, particularly in childhood. MBL deficiency is associated with a number of diseases, including rheumatoid arthritis, systemic lupus erythematosus, and Crohn's disease. Conversely, high levels of MBL are associated with nephropathy in type 1 diabetes and may contribute to tissue damage in autoimmune diseases.

See also

• Complement system
• Innate immune system
• Lectin pathway
• Collectin

References

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