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a trodden path (同)footpath
any of several plant glycoproteins that act like specific antibodies but are not antibodies in that they are not evoked by an antigenic stimulus

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/09/14 20:36:44」(JST)

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Natta projection of mannose in its α-D-mannopyranose form. Mannan is a polymer of mannose.

The lectin pathway is similar in structure to the classical complement pathway,^[1] in that, after activation, it proceeds through the action of C4 and C2 to produce activated complement proteins further down the cascade. In contrast to the classical complement pathway, the lectin pathway does not recognize antibody bound to its target. The lectin pathway starts with mannose-binding lectin or ficolin binding to certain sugars.

In this pathway, mannose-binding lectin binds to mannose, glucose or other sugars with 3- and 4-OH groups placed in the equatorial plane, in terminal positions on carbohydrate or glycoprotein components of microorganisms including bacteria such as Salmonella, Listeria, and Neisseria strains. Fungal pathogens such as Candida albicans and Cryptococcus neoformans as well as some viruses such as HIV-1 and Respiratory syncytial virus (RSV) are bound by MBL.

Mannan-binding lectin (MBL, also called mannose-binding protein) is a protein belonging to the collectin family that is produced by the liver and can initiate the complement cascade by binding to pathogen surfaces.

MBL

MBL is a 6- to 18-headed molecule that forms a complex with MASP-1 (Mannan-binding lectin-Associated Serine Protease), MASP-2 and MASP-3, that are protease zymogens. The MASPs are very similar to C1r and C1s molecules of the classical complement pathway, respectively, and are thought to have a common evolutionary ancestor. When the carbohydrate-recognising heads of MBL bind to specifically arranged mannose residues on the surface of a pathogen, MASP-1 and MASP-2 are activated to cleave complement components C4 and C2 into C4a, C4b, C2a, and C2b. In addition, two smaller MBL-associated proteins (MAps) are found in complex with MBL. MBL-associated protein of 19 kDa (MAp19) and MBL-associated protein of 44 kDa (Map44). MASP-1, MASP-3 and MAp44 are alternative splice products of the MASP1 gene, while MASP-2 and MAp19 are alternative splice products of the MASP-2 gene. MAp44 has been suggested to act as a competitive inhibitor of lectin pathway activation, by displacing MASP-2 from MBL, hence preventing cleavage of C4 and C2 ^[2]

C3 convertase

C4b and C2a combine on the surface of the pathogen to form C3 convertase (C4b and C2a), while C4a and C2b act as chemoattractants.

C3 convertase is, in classical terms, C4b2a.

Clinical significance

It has been found that people deficient in MBL experience a substantial increase in infections during the early years of childhood.

References

^ Wallis R, Mitchell DA, Schmid R, Schwaeble WJ, Keeble AH (2010). "Paths reunited: Initiation of the classical and lectin pathways of complement activation". Immunobiology 215 (1): 1–11. doi:10.1016/j.imbio.2009.08.006. PMC 2824237. PMID 19783065. http://linkinghub.elsevier.com/retrieve/pii/S0171-2985(09)00146-6.
^ Degn, Søren; Annette G. Hansen, Rudi Steffensen,Christian Jacobsen, Jens C. Jensenius and Steffen Thiel (November 2009). "MAp44, a Human Protein Associated with Pattern Recognition Molecules of the Complement System and Regulating the Lectin Pathway of Complement Activation". Journal of Immunology 183 (11): 7371–7378. doi:10.4049/jimmunol.0902388. PMID 19917686. http://www.jimmunol.org/cgi/content/full/183/11/7371.

External links

http://pathmicro.med.sc.edu/ghaffar/complement.htm

This immunology article is a stub. You can help Wikipedia by expanding it.

UpToDate Contents

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1. マンノース結合レクチン mannose binding lectin
2. 補体経路 complement pathways
3. 補体系の遺伝性疾患 inherited disorders of the complement system
4. マンノース結合レクチン欠損症 mannose binding lectin deficiency
5. 補体系の概要および臨床的評価 overview and clinical assessment of the complement system

English Journal

Molecular and structural basis for N-glycan-dependent determination of glycoprotein fates in cells.

Kamiya Y, Satoh T, Kato K.SourceOkazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan; Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
Biochimica et biophysica acta.Biochim Biophys Acta.2012 Sep;1820(9):1327-37. Epub 2012 Jan 5.
BACKGROUND: N-linked oligosaccharides operate as tags for protein quality control, consigning glycoproteins to different fates, i.e. folding in the endoplasmic reticulum (ER), vesicular transport between the ER and the Golgi complex, and ER-associated degradation of glycoproteins, by interacting wit
PMID 22240168

Circulating ficolin-2 and ficolin-3 in normal pregnancy and pre-eclampsia.

Halmos A, Rigó J Jr, Szijártó J, Füst G, Prohászka Z, Molvarec A.SourceFirst Department of Obstetrics and Gynecology Third Department of Internal Medicine, Semmelweis University Research Group of Inflammation Biology and Immunogenomics, Hungarian Academy of Sciences, Budapest, Hungary.
Clinical and experimental immunology.Clin Exp Immunol.2012 Jul;169(1):49-56. doi: 10.1111/j.1365-2249.2012.04590.x.
Ficolins are soluble molecules of the innate immune system that recognize carbohydrate molecules on microbial pathogens, apoptotic and necrotic cells. They act through two distinct routes: initiating the lectin pathway of complement activation and mediating a primitive opsonophagocytosis. In this st
PMID 22670778

Japanese Journal

ランゲルハンス細胞とHIV

川村龍吉
日本臨床免疫学会会誌 = Japanese journal of clinical immunology 34(2), 70-75, 2011-04-28
世界における新規ヒト免疫不全ウイルス（HIV）感染の約8割は異性間の性的接触による．粘膜・皮膚表皮内ランゲルハンス細胞（LC）は，HIV感染初期においてHIVに対する初期免疫応答の誘導に重要な役割を担っている．さらに，LCに発現されるLangerinに捕獲されたHIVは不活化を受けることが最近明らかとなり，LCはHIVの侵入を防ぐバリアーとしても機能する．一方，Langer …
NAID 10029431867

Stable coexpression of two human sialylation enzymes in plant suspension-cultured tobacco cells(PLANT BIOTECHNOLOGY)

Kajiura Hiroyuki,Misaki Ryo,Fujiyama Kazuhito,Seki Tatsuji
Journal of bioscience and bioengineering 111(4), 471-477, 2011-04
… In this study, we introduced hCSS and hST genes into suspension-cultured tobacco BY2 cells to provide the machinery for the sialylation pathway in plants. … Furthermore, the results of the purification of the coupled-reaction products by Sambucus sieboldian lectin column chromatography and digestion with linkage-specific neuraminidase revealed that the modified terminal residue was α2,6-linked NeuAc. …
NAID 110008607505

Related Pictures

★リンクテーブル★

リンク元	「補体」「フィコリン」
関連記事	「pathway」

「補体」

　　[★]

英: complement
同: アレキシン alexin
関: 補体活性化経路、補体価

図：IMM.63

pathway	start	first step
classical pathway	antigen-antibody complex	C1q, C1r, C1s, C4, C2
lectin pathway	mannose-binding lectin or ficolin binds carbohydrate on pathogen surface	MBL/ficolin, MASP-2, C4, C2
alternative pathway	pathogen surface	C3, B, D

補体の相互作用 IMM.62

古典的経路 classical pathway

C1qがカスケードの最初となる。3つの方法で補体カスケードがはじまる。

(1)多価陰イオン表面(例えば、グラム陰性細菌のリポテイコ酸)
(2)バクテリアの多糖のホスホコリンに結合(例えば肺炎球菌のC蛋白質)
(3)抗原抗体複合体に結合して自然免疫と獲得免疫のエフェクター機構を結びつける。

レクチン経路 lectin pathway

炭化水素鎖を認識するレクチンがカスケードの最初となる。

1. lectin MBL：mannose-containing carbohydrates
2. ficolin　：N-acetylglucosamine

代替経路 alternative pathway

C3からはじまる。血漿中のC3が病原体の表面で自発的に活性化されることで補体反応がはじまる。

３つの経路は共通してC3 convertaseを生成。C3 convertaseはC3→C3a+C3b
C3a: C3a is a peptide mediator of local inflammation
C3b: C3b binds covalently to the bacterial cell membrane and opsonizes the bacteria

C5 convertaseはC3bにC3 convertaseが結合してできる
C5 converaseはC5→C5a+C5b
C5a: powerful peptide mediator of inflammation
C5b: C5b,C6,C7,C8,C9: membrane-attack complex

C3aとC5a。C4a

炎症部位に血管外に抗体、補体、食細胞を集め、組織液を増やすことで抗原提示細胞がリンパ節に移動するのを促進する(IMM.75)

C5a,C3a,C4a: smooth muscle contraction.(IMM.75)
C5a,C3a: act on the endo thelial cells lining blood vessels to induce adhesion molecules.(IMM.75)
C5a>C3a>C4a: increase in blood flow, increase vascular permeability, increase binding of phagocytes to exdothielial cells.(IMM.76)
C5a: activates mast cells to release mediators, such as histamine and TNF-α. that contribute the inflammatory response(IMM.76).
C5a: acts directly on neutrophils and monocytes and attracting neutrophils and monocytes(IMM.75)
C3a: contributes to the pypotension and edema seen in endotoxic shock
C5a: activated by endotoxin, funcions in neutrophil chemotaxis