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C2b is the smallest , enzymatically active, fragment of C3 convertase in this pathway, C4b2b (NB: [[Complement system#Complement protein fragment nomenclature|some sources now refer]] to the larger fragment of C2 as C2b, making the C3 convertase C4b2b, whereas older sources refer to the larger fragment of C2 as C2a, making the C3 convertase C4b2a). The smaller fragment, C2a (or C2b, depending on the source) is released into the fluid phase.<ref name="c2 fragment structure">{{cite journal | vauthors = Krishnan V, Xu Y, Macon K, Volanakis JE, Narayana SV | title = The structure of C2b, a fragment of complement component C2 produced during C3 convertase formation | journal = Acta Crystallographica D | volume = 65 | issue = Pt 3 | pages = 266–274 | year = 2009 | pmid = 19237749 | pmc = 2651757 | doi = 10.1107/S0907444909000389 }}</ref>
== Clinical signficance ==
== Complement Component 2 Deficiency ==
Deficiency of the complement component 2 protein causes a malfunction in the [[immune system]].<ref name = "Medline">{{cite web | title = Complement component 2 deficiency | url = https://medlineplus.gov/genetics/condition/complement-component-2-deficiency/ | work = Medline Plus | publisher = U.S. National Libray of Medicine }}</ref> This malfunction results in a significantly increased risk of [[bacterial infection]]s as well as [[autoimmune disorder]]s such as [[systemic lupus erythematosus]] (SLE) and [[vasculitis]].<ref name = "Medline" /><ref name="Sjöholm_2006">{{cite journal | vauthors = Sjöholm AG, Jönsson G, Braconier JH, Sturfelt G, Truedsson L | title = Complement deficiency and disease: an update | journal = Molecular Immunology | volume = 43 | issue = 1-2 | pages = 78–85 | date = January 2006 | pmid = 16026838 | doi = 10.1016/j.molimm.2005.06.025 }}</ref><ref name="Wen_2004">{{cite journal | vauthors = Wen L, Atkinson JP, Giclas PC | title = Clinical and laboratory evaluation of complement deficiency | journal = The Journal of Allergy and Clinical Immunology | volume = 113 | issue = 4 | pages = 585–93; quiz 594 | date = April 2004 | pmid = 15100659 | doi = 10.1016/j.jaci.2004.02.003 }}</ref>
[[File:Protein_C2_PDB_2i6q.png|thumb|'''Complement C2''' is a protein that in humans is encoded by the C2 gene.]]
'''In the Molecular Biology,''' the [https://www.sciencedirect.com/topics/medicine-and-dentistry/complement-component-c2 deficiency of Complement Component 2 i]s a disorder that causes a major effect in the immune system, resulting in a form of immunodeficiency. This effect results in an inability to protect the body against any foreign invader. Complement component 2 deficiency is also connected with an increased risk of developing autoimmune disorders, such as systemic vasculitis. Complement deficiencies is a challenge to understand due to insufficient clinical trails. Using a hemolytic-plaque assay, RNA extraction, and blot analysis, it is fair to note that complement component 2 deficiency is a result of pre-translational regulatory detect in C2 gene expression. This detects a lack of synthesis within the C2 protein. This deficiency can be further understood by incorporating plasma protein deficiencies, especially those in tissue macrophages. It is also important to note that Complement component 2 deficiency can be caused by genetic and environmental factors. In genetic inheritance, Autosomal recessive conditions are inherited with mutations in both copies of the gene where parents of autosomal recessive condition typically do not show symptoms.
== Development of SLE ==
Complement component 2 deficiency is associated with an increased risk of developing autoimmune disorders, with females more likely to have SLE. Systemic lupus erythematosus (lupus) is a chronic autoimmune disease that causes inflammation and tissue damage, affecting many parts of the body. Lupus can range from mild to severe and can cause inflammation in organs, such as joints, skin, kidneys, and brain. The severity of the disorder varies.
C2 is an important component of both the classical and lectin pathways of complement activation, and is essential for first line defense against [https://bmcimmunol.biomedcentral.com/articles/10.1186/1471-2172-11-43 microbial infection.] It binds to MBL or ficolins to form the C3 convertase C4b2a. In C2 deficiency, C3 is not efficiently cleaved, leading to limited deposition of C3 fragments on immune complexes and apoptotic cells, leading to chronic activation of the complement system.
== Treatment and Management ==
'''Complement deficiency''' is managed on a case-by-case basis with antibiotics and regular visits with an immunologist. A form to treat complement component 2 deficiency includes replacing the missing component of the cascade, either through direct infusion of the protein or through gene therapy. Patients should be aware of symptoms of meningococcal infection and receive routine vaccinations. Patients should seek for accessible resources offered by the medical provider and take the necessary actions needed to treat for complement deficiency.
== Patient Education ==
Patients and parents should be educated on the symptoms of serious illness and seek care immediately. Vaccination is an important preventive measure for the deficiency of complement component 2. Early diagnosis, antibiotic prophylaxis, and vaccinations can help prevent life-threatening infections in hereditary C2 deficiency.
== Promoting Health Care Outcomes ==
The interprofessional team must be aware of the clinical features of patients with complement deficiency or immunodeficiency, and refer them to allergist/immunologists when necessary.
== References ==
{{Reflist}}
<small>1. Jonsson G, Truedsson L, Sturfelt G, Oxelius VA, Braconier JH, Sjoholm AG. Hereditary C2 deficiency in Sweden: frequent occurrence of invasive infection, atherosclerosis, and rheumatic disease. Medicine (Baltimore). 2005Jan;84(1):23-34. doi: 10.1097/01.md.0000152371.22747.1e. Citation on PubMed (https://pubmed.ncb i.nlm.nih.gov/15643297)
2. Complement+2 at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
Sjöholm AG, Jönsson G, Braconier JH, Sturfelt G, Truedsson L. Complement deficiency and disease: an update. Mol Immunol. 2006 Jan;43(1-2):78-85. doi: 10.1016/j.molimm.2005.06.025. PMID: 16026838.
3. Wen L, Atkinson JP, Giclas PC. Clinical and laboratory evaluation of complement deficiency. J Allergy Clin Immunol. 2004 Apr;113(4):585-93; quiz 594. doi: 10.1016/j.jaci.2004.02.003. PMID: 15100659.
4. Chen HH, Tsai LJ, Lee KR, Chen YM, Hung WT, Chen DY. Genetic association of complement component 2 polymorphism with systemic lupus erythematosus. Tissue Antigens. 2015 Aug;86(2):122-33. doi: 10.1111/tan.12602. Epub 2015 Jul 14. PMID: 26176736.</small>
== Further reading ==
* {{cite journal | vauthors = Parkes C, Gagnon J, Kerr MA | title = The reaction of iodine and thiol-blocking reagents with human complement components C2 and factor B. Purification and N-terminal amino acid sequence of a peptide from C2a containing a free thiol group | journal = The Biochemical Journal | volume = 213 | issue = 1 | pages = 201–209 | date = Jul 1983 | pmid = 6555044 | pmc = 1152109 | doi = 10.1042/bj2130201}}
* {{cite journal | vauthors = Kerr MA, Gagnon J | title = The purification and properties of the second component of guinea-pig complement | journal = The Biochemical Journal | volume = 205 | issue = 1 | pages = 59–67 | date = Jul 1982 | pmid = 6922702 | pmc = 1158446 | doi = 10.1042/bj2050059}}
* {{cite book | vauthors = Liu C-CCC, Ahearn JM | chapter = Chap. 13: Complement and systemic lupus erythematosus. | edition = 7th ed.| In:veditors = Wallace DJ, Hahn BH, editors.| title = Dubois’ Lupus Erythematosus. (Chap.| 13),___location = Philadelphia:| publisher = Lippincott Williams & Wilkins (| date = 2007). p.| 214–35.pages = 214–235 }}
* {{cite journal | vauthors = Grammatikos AP, Tsokos GC. | title = Immunodeficiency and autoimmunity: lessons from systemic lupus erythematosus. | journal = Trends Molin MedMolecular (2012)Medicine | volume = 18: | issue = 2 | pages = 101–8. | date = February 2012 | pmid = 22177735 | pmc = 3278563 | doi: = 10.1016/j.molmed.2011.10.005 }}
* {{cite journal | vauthors = Ippolito A, Wallace DJ, Gladman D, Fortin PR, Urowitz M, Werth V, etCostner al.M, AutoGordon C, Alarcón GS, Ramsey-antibodiesGoldman R, Maddison P, Clarke A, Bernatsky S, Manzi S, Bae SC, Merrill JT, Ginzler E, Hanly JG, Nived O, Sturfelt G, Sanchez-Guerrero J, Bruce I, Aranow C, Isenberg D, Zoma A, Magder LS, Buyon J, Kalunian K, Dooley MA, Steinsson K, van Vollenhoven RF, Stoll T, Weisman M, Petri M | display-authors = 6 | title = Autoantibodies in systemic lupus erythematosus: comparison of historical and current assessment of seropositivity. | journal = Lupus (2011)| volume = 20:250–5. | issue = 3 | pages = 250–255 | date = March 2011 | pmid = 21362750 | doi: = 10.1177/0961203310385738 }}
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