Definition:

There is an increasing number of clinical studies indicating that deficiency of the lectin pathway has been associated with an increased risk, severity, and frequency of infections but also autoimmune disorders. MBL deficiency is one of the most common human immunodeficiencies and arises primarily from three single point mutations in exon 1 of the MBL-2 gene. These mutations result in a failure to assemble fully functional multimeric protein. Inherited MASP-2 deficiency has been described as the result of a mutation causing the exchange of aspartic acid with a glycine at position 105, a position in the first domain, CUB1, involved in calcium binding. This mutation abolishes the binding to MBL and ficolins, and deprives MASP-2 of functional activity.