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Genetic and Rare Diseases Information Center (GARD)

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Mannose-binding lectin protein deficiency


* Not a rare disease
Other Names for this Disease
  • Mannose-binding protein deficiency
  • MBL deficiency
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What causes mannose-binding lectin protein (MBL) deficiency?

MBL deficiency can occur as a result of one or more variations in the MBL2 gene, which codes for the MBL protein. A lack of this protein can cause this condition, but it is likely further influenced by other genetic and environmental factors that are currently poorly understood.[1] 

The mannose-binding lectin (MBL) protein is excreted by the liver and is part of our innate immune defense. This protein binds to sugars on the surface of microorganisms to signal their destruction and triggers one of the major complement cascades called the “mannose-binding lectin (MBL) pathway.” Complement cascades are made up of proteins that work together to destroy bacteria and other antigens. The mannose binding protein circulates in the blood in an inactive form. When it is activated it sets in motion a domino effect where each component of the mannose-binding lectin pathway takes its turn in a precise chain of steps. The end products from the cascade are able to destroy invading bacteria and other antigens.[2] 

More information on immune system responses can be found at the following link from MedlinePlus, the National Library of Medicine Web site designed to help you research your health questions.
Last updated: 4/9/2012

  1. Eisen DP. Mannose-binding lectin deficiency and respiratory tract infection. J Innate Immun. February 2010; Accessed 1/9/2012.
  2. Immune system, Complement system. National Institute of Allergy and Infectious Disease. October 2008; Accessed 1/9/2012.