What are the genetic changes related to mannose-binding lectin deficiency ?
Relatively common mutations in the MBL2 gene can lead to mannose-binding lectin deficiency. This gene provides instructions for making a protein that assembles into a complex called mannose-binding lectin. Functional mannose-binding lectins are made up of two to six protein groups called trimers, which are each composed of three of the protein pieces (subunits) produced from the MBL2 gene.  Mannose-binding lectin plays an important role in the body's immune response by attaching to foreign invaders such as bacteria, viruses, or yeast and turning on (activating) the complement system. The complement system is a group of immune system proteins that work together to destroy foreign invaders (pathogens), trigger inflammation, and remove debris from cells and tissues. Mannose-binding lectin can also stimulate special immune cells to engulf and break down the attached pathogen.  Disease-associated mutations in the MBL2 gene can reduce the production of the mannose-binding lectin subunit or eliminate the subunit's ability to assemble into functional mannose-binding lectin. A decrease in the availability of the normal subunit protein may lead to a reduction of the functional mannose-binding lectin in blood. With decreased levels of mannose-binding lectin, the body does not recognize and fight foreign invaders efficiently. Consequently, infections can be more common in people with this condition.  However, not everyone with a change in the MBL2 gene has decreased levels of mannose-binding lectin, and not everyone with decreased protein levels is prone to infection. Researchers believe that a number of factors, including other genetic and environmental factors, are involved in the development of mannose-binding lectin deficiency and susceptibility to infection.