class switching

同

isotype

関

isotype switching

WordNet

1. elegance in dress or behavior; "she has a lot of class"
2. a collection of things sharing a common attribute; "there are two classes of detergents" (同)category, family
3. a league ranked by quality; "he played baseball in class D for two years"; "Princeton is in the NCAA Division 1-AA" (同)division
4. a body of students who are taught together; "early morning classes are always sleepy" (同)form, grade, course
5. people having the same social, economic, or educational status; "the working class"; "an emerging professional class" (同)stratum, social_class, socio-economic class
6. a body of students who graduate together; "the class of 97"; "she was in my year at Hoehandle High" (同)year
7. (biology) a taxonomic group containing one or more orders

PrepTutorEJDIC

1. 〈C〉(何らかの類似性を持つ)(…の)『種類』,類(sort, kind)《+『of』+『名』》 / 〈C〉《集合的に》《単数扱い》『クラス』,学級,組 / 〈U〉〈C〉(クラス単位の)『授業』;授業時間 / 〈C〉《米》《集合的に》(主に高校・大学の)同期生 / 〈C〉《しばしば複数形で》(同程度の教育・経済力・社会的地位などを持つ)『階級』,階層 / 〈C〉(交通機関などの)『等級』 / 〈C〉(英国の大学の)試験の合格等級 / 〈C〉綱(こう)(動植物の分類で門(phylum, division)と目(もく)(order)の間) / 〈U〉《話》(その人の社会的地位を高く見せる)風格 / …'を'(…の)部類に入れる《+『名』+『among』(『with』)+『名』》,(…として)…'を'分類する《+『名』+『as』+『名』》

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/05/06 22:03:09」(JST)

wiki en

[Wiki en表示]

Mechanism of class switch recombination that allows isotype switching in activated B cells

Immunoglobulin class switching (or isotype switching or isotypic commutation or class switch recombination(CSR)) is a biological mechanism that changes a B cell's production of antibody from one class to another, for example, from an isotype called IgM to an isotype called IgG. During this process, the constant region portion of the antibody heavy chain is changed, but the variable region of the heavy chain stays the same (the terms "constant" and "variable" refer to changes or lack thereof between antibodies that target different epitopes). Since the variable region does not change, class switching does not affect antigen specificity. Instead, the antibody retains affinity for the same antigens, but can interact with different effector molecules.

Mechanism

Class switching occurs after activation of a mature B cell via its membrane-bound antibody molecule (or B cell receptor) to generate the different classes of antibody, all with the same variable domains as the original antibody generated in the immature B cell during the process of V(D)J recombination, but possessing distinct constant domains in their heavy chains.

Naïve mature B cells produce both IgM and IgD, which are the first two heavy chain segments in the immunoglobulin locus. After activation by antigen, these B cells proliferate. If these activated B cells encounter specific signaling molecules via their CD40 and cytokine receptors (both modulated by T helper cells), they undergo antibody class switching to produce IgG, IgA or IgE antibodies. During class switching, the constant region of the immunoglobulin heavy chain changes but the variable regions, and therefore antigenic specificity, stay the same. This allows different daughter cells from the same activated B cell to produce antibodies of different isotypes or subtypes (e.g. IgG1, IgG2 etc.).

The order of the heavy chain exons are as follows:

• μ - IgM
• δ - IgD
• γ3 - IgG3
• γ1 - IgG1
• pseudogene similar to ε gene that is not used
• α1 - IgA1
• γ2 - IgG2
• γ4 - IgG4
• ε - IgE
• α2 - IgA2^{[citation needed]}

Class switching occurs by a mechanism called class switch recombination (CSR) binding. Class switch recombination is a biological mechanism that allows the class of antibody produced by an activated B cell to change during a process known as isotype or class switching. During CSR, portions of the antibody heavy chain locus are removed from the chromosome, and the gene segments surrounding the deleted portion are rejoined to retain a functional antibody gene that produces antibody of a different isotype. Double-stranded breaks are generated in DNA at conserved nucleotide motifs, called switch (S) regions, which are upstream from gene segments that encode the constant regions of antibody heavy chains; these occur adjacent to all heavy chain constant region genes with the exception of the δ-chain. DNA is nicked and broken at two selected S-regions by the activity of a series of enzymes, including Activation-Induced (Cytidine) Deaminase (AID), uracil DNA glycosylase and apyrimidic/apurinic (AP)-endonucleases. The intervening DNA between the S-regions is subsequently deleted from the chromosome, removing unwanted μ or δ heavy chain constant region exons and allowing substitution of a γ, α or ε constant region gene segment. The free ends of the DNA are rejoined by a process called non-homologous end joining (NHEJ) to link the variable domain exon to the desired downstream constant domain exon of the antibody heavy chain. In the absence of non-homologous end joining, free ends of DNA may be rejoined by an alternative pathway biased toward microhomology joins. With the exception of the μ and δ genes, only one antibody class is expressed by a B cell at any point in time.

Cytokines responsible for class switching

T cell cytokines are responsible for class switching in mouse (Table 1) and human (Table 2). These cytokines may have suppressive effect on production of IgM.

Table 1. Class switching in mouse

T cells	Cytokines	Immunoglobulin classes
		IgG1	IgG2a	IgG2b	IgG3	IgA	IgE
Th2	IL-4	↑	↓	↓	↓	↓	↑
	IL-5					↑
Th1	IFNγ	↓	↑	↓	↓	↓	↓
Treg	TGFβ			↑	↓	↑

Table 2. Class switching in human

T cells	Cytokines	Immunoglobulin classes
		IgG1	IgG2	IgG3	IgG4	IgA	IgE
Th2	IL-4				↑		↑
	IL-5					↑
Th1	IFNγ
Treg	TGFβ					↑

See also

• immunogenetics
• antibody

References

External links

• MeSH Immunoglobulin+class+switching
• Diagram and description at med.sc.edu (see Figure 10)
• Diagram at umassmed.edu
• Diagram and description at cam.ac.uk
• Diagram at utoronto.ca

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

• 1. 成人における双極性障害：抗うつ剤による大うつ病エピソードの治療 bipolar disorder in adults treating major depression with antidepressants
• 2. 免疫遺伝学 immunoglobulin genetics
• 3. 移植免疫 transplantation immunobiology
• 4. 関節リウマチにおけるHLAおよびその他の感受性遺伝子 hla and other susceptibility genes in rheumatoid arthritis
• 5. 成人における単極性うつ病：難治性うつ病の治療 unipolar depression in adults treatment of resistant depression

English Journal

• Heme binds to an intrinsically disordered region of Bach2 and alters its conformation.

• Watanabe-Matsui M1, Matsumoto T2, Matsui T3, Ikeda-Saito M3, Muto A1, Murayama K4, Igarashi K5.
• Archives of biochemistry and biophysics.Arch Biochem Biophys.2015 Jan 1;565:25-31. doi: 10.1016/j.abb.2014.11.005. Epub 2014 Nov 18.
• The transcriptional repressor Bach2 regulates humoral and cellular immunity, including antibody class switching. It possesses a basic leucine zipper domain that mediates DNA binding. Heme inhibits the DNA-binding activity of Bach2 in vitro and induces the degradation of Bach2 in B cells. However, th
• PMID 25444856

• Silencing miR-146a influences B cells and ameliorates experimental autoimmune myasthenia gravis.

• Zhang J1, Jia G, Liu Q, Hu J, Yan M, Yang B, Yang H, Zhou W, Li J.
• Immunology.Immunology.2015 Jan;144(1):56-67. doi: 10.1111/imm.12347.
• MicroRNAs have been shown to be important regulators of immune homeostasis as patients with aberrant microRNA expression appeared to be more susceptible to autoimmune diseases. We recently found that miR-146a was up-regulated in activated B cells in response to rat acetylcholine receptor (AChR) α-s
• PMID 24962817

• Mast cells, basophils and B cell connection network.

• Merluzzi S1, Betto E2, Ceccaroni AA2, Magris R2, Giunta M3, Mion F2.
• Molecular immunology.Mol Immunol.2015 Jan;63(1):94-103. doi: 10.1016/j.molimm.2014.02.016. Epub 2014 Mar 23.
• It has been proven that both resting and activated mast cells (MCs) and basophils are able to induce a significant increase in proliferation and survival of naïve and activated B cells, and their differentiation into antibody-producing cells. The immunological context in which this regulation occur
• PMID 24671125

Japanese Journal

• Intracellular Delivery of Lipopolysaccharide Induces Effective Th1-Immune Responses Independent of IL-12.

• Watanabe Sachiko,Inoue Joe
• PloS one 8(7), 2013-07-00
• … It is thought that IL-12 is required for one of the protective immune responses induced by LPS, the T helper 1 (Th1)-immune response, which include the production of IFN-γ from Th1cells and IgG2c class switching. …
• NAID 120005306995

• M12-Tet-Off pTRE2pur FLAG mTRAF3細胞株の樹立

• 田邊 香野,坂本 瞳,乾 誠治,タナベ カノ,サカモト ヒトミ,イヌイ セイジ,Tanabe Kano,Sakamoto Hitomi,Inui Seiji
• 熊本大学医学部保健学科紀要 9, 27-38, 2013-03-30
• … IL-4 induces IgE class switching in B cells together with CD40 stimulation. …
• NAID 110009555909

• Design Equations for Off-Nominal Operation of Class E Amplifier with Nonlinear Shunt Capacitance at D=0.5

• SUETSUGU Tadashi,WEI Xiuqin,KAZIMIERCZUK Marian K.
• IEICE Transactions on Communications E96.B(9), 2198-2205, 2013
• … Design equations for satisfying off-nominal operating conditions of the class E amplifier with a nonlinear shunt capacitance for a grading coefficient of 0.5 and the duty cycle D=0.5 are derived. … By exploiting the off-nominal class E operation, various amplifier parameters such as input voltage, operating frequency, output power, and load resistance can be set as design specifications. …
• NAID 130003370273

Related Links

• class switching - definition of class switching in the Medical ...

class 1. a group of similar objects or values selected as a part of a classification. 2. a taxonomic category subordinate to a phylum and superior to an order. 3. a group of variables all of which show a value falling between certain limits.

• Class switching - definition of Class switching by the Free ...

class (klăs) n. 1. A set, collection, group, or configuration containing members regarded as having certain attributes or traits in common; a kind or category. 2. A division based on quality, rank, or grade, as: a. A grade of mail: a ...

Related Pictures

---

★リンクテーブル★

拡張検索	「immunoglobulin class switching」
関連記事	「class」「switching」

「immunoglobulin class switching」

　　[★]

免疫グロブリンクラススイッチ

関

class switching、isotype switching

「class」

　　[★]

• n.

• クラス、分類、種類、部門、(分類学)綱

関

assortment、branch、categorization、categorize、category、classification、classifier、classify、department、division、group、grouping、kind、pattern、section、sector、sort、systematization、typing

　 　 　 　 　 　 　 　

「switching」

　　[★]

• n.

• 転換、スイッチング

関

changeover、conversion、convert、diversion、interconversion、shift、switch