微生物の表面に存在する繰り返しスパーターンの分子構造を認識する仕組み。病原体関連分子パターンを認識する、パターン認識レセプターのひとつ。
血漿中のタンパク質として存在し、補体活性化のレクチン経路を開始することが出来る。コラーゲンに類似したドメインとC型レクチンのドメインをひとつずつもち（コレクチン）パターン認識受容体として微生物細胞表面に規則正しく並んだマンノースまたはフコースと結合し、貪食細胞により処理される。（オプソニン化）
マクロファージがもつマンノースレセプターもMBLとよく似た仕組みで病原体（細菌やHIVなど）を認識する。
Mannose-binding protein C
Short name=MBP-C
Alternative name(s):
Collectin-1
MBP1
Mannan-binding protein
Mannose-binding lectin
:Function
Calcium-dependent lectin involved in innate immune defense. Binds mannose, fucose and N-acetylglucosamine on different microorganisms and activates the lectin complement pathway. Binds to late apoptotic cells, as well as to apoptotic blebs and to necrotic cells, but not to early apoptotic cells, facilitating their uptake by macrophages. May bind DNA. Ref.11
Subunit structure
Oligomeric complex of 3 or more homotrimers. Interacts with MASP1 and MASP2. Interacts with MEP1A and MEP1B and may inhibit their catalytic activity. Ref.10 Ref.13
Subcellular location
Secreted Ref.9.
Tissue specificity
Plasma protein produced mainly in the liver. Ref.14
Polymorphism
Genetic variations in MBL2 influence susceptibility to hepatitis B virus (HBV) infection [MIM:610424].
Genetic variations in MBL2 are responsible for mannose-binding protein deficiency [MIM:614372]. This condition is defined as MBL2 protein level of less than 100 ng/ml, is present in about 5% of people of European descent and in about 10% of sub-Saharan Africans. Most MBL2-deficient adults appear healthy, but low levels of MBL2 are associated with increased risk of infection in toddlers, in cancer patients undergoing chemotherapy, and in organ-transplant patients receiving immunosuppressive drugs, particularly recipients of liver transplants. There is an association between low levels of MBL2 and a defect of opsonization which results in susceptibility to frequent and chronic infections (Ref.16). Functional MBL2 deficiency may be associated with protection against tuberculosis caused by Mycobacterium africanum but not by Mycobacterium tuberculosis, as observed in studies on Ghanaian patients with pulmonary tuberculosis (Ref.22).
Sequence similarities
Contains 1 C-type lectin domain.
Contains 1 collagen-like domain.
