Complement Activation, Classical Pathway (Bos taurus)

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Description

The complement system is a biochemical cascade that helps, or complements, the ability of antibodies to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime. However, it can be recruited and brought into action by the adaptive immune system. The Classical pathway of activation of the complement system is a group of blood proteins that mediate the specific antibody response. [source: Wikipedia]

The Classical pathway begins with circulating C1Q binding to an antigen on the surface of a pathogen, which goes on to active and recruit 2 copies of each C1R and C1S, forming a C1 complex. The activated C1 complex cleaves C2 and C4. Activated cleavage products C2A and C4B combine to form C3 convertase, which cleaves C3. The cleavage product C3B joins the complex to form C5 convertase, which cleaves C5. The cleavage product C5B joins C6, C7, C8 and multiple copies of C9 to form the Membrane Attack Complex, which forms a channel for water to flood into the target cell, leading to osmotic lysis. The Decay accelerating factor (DAF) inhibits C3 convertase.

The Lectin pathway involves mannose-binding lectin (MBL) binding the surface of the pathogen instead of C1Q. MBL-associated serine proteases MASP1 and MASP1 can cleave C2 and C4 in place of the C1 complex, leading to the formation of C3 convertase and the subsequent cascade.

The Alternative pathway relies on the spontaneous hydrolysis of C3 and the cleavage of factor B (CFB) by factor D (CFD), which form an alternative C3 convertase stabilized by factor P (CFP). Additional copies of the cleavage product C3B are recruited to the complex, resulting in an alternative C5 convertase, which cleaves C5 and contributes C5B to the formation of the Membrane Attack Complex.

Comments

HomologyConvert 
This pathway was inferred from Homo sapiens pathway WP545(72062) with a 100.0% conversion rate.

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Ontology Terms

 

Bibliography

  1. Brook E, Herbert AP, Jenkins HT, Soares DC, Barlow PN; ''Opportunities for new therapies based on the natural regulators of complement activation.''; Ann N Y Acad Sci, 2005 PubMed

History

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CompareRevisionActionTimeUserComment
89917view13:31, 6 October 2016MkutmonOntology Term : 'immune response pathway' added !
89916view13:31, 6 October 2016MkutmonOntology Term : 'classical complement pathway' added !
89915view13:31, 6 October 2016MkutmonOntology Term : 'innate immune response pathway' added !
89914view13:30, 6 October 2016MkutmonModified description
80673view15:21, 30 June 2015Mkutmonhomology conversion
63463view17:19, 10 May 2013MaintBotUpdated to 2013 gpml schema
40598view19:34, 1 March 2011MaintBotRemoved redundant pathway information and comments
33835view00:30, 9 December 2009MaintBotAutomatic update of empty xrefs
33622view10:02, 1 December 2009MaintBotRemoved group label
31636view22:24, 13 August 2009MaintBotFixed text labels
30546view21:58, 29 July 2009MaintBotNew pathway

External references

Datanodes

View all...
NameTypeDatabase referenceComment
C1QAGeneProductENSBTAG00000007153 (Ensembl)
  • update: C1QA HUMAN
  • HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:712
C1QBGeneProductENSBTAG00000011196 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:713
C1QCGeneProductENSBTAG00000011193 (Ensembl)
  • update C1QC HUMAN
  • HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:714
C1RGeneProductENSBTAG00000037743 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = En:ENSG00000159403
C1SGeneProductENSBTAG00000004840 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:716
C2GeneProductENSBTAG00000007450 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:717
C3GeneProductENSBTAG00000017280 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:718
C4AGeneProductENSBTAG00000006864 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:720
C4BGeneProductENSBTAG00000006864 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:721
C5GeneProductENSBTAG00000012210 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:727
C6GeneProductENSBTAG00000014177 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:729
C7GeneProductENSBTAG00000011766 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:730
C8AGeneProductENSBTAG00000003774 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:731
C8BGeneProductENSBTAG00000003775 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:732
C9GeneProductENSBTAG00000016149 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:735
CD55GeneProductENSBTAG00000006984 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:1604
H2OMetaboliteHMDB02111 (HMDB)
MASP1GeneProductENSBTAG00000012467 (Ensembl) HomologyConvert: Homo sapiens to Bos taurus: Original ID = L:5648

Annotated Interactions

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