Paratope

In immunology, a paratope, also known as an antigen-binding site, is the part of an antibody which recognizes and binds to an antigen.^[1]^[2] It is a small region at the tip of the antibody's antigen-binding fragment and contains portions of the antibody's heavy chain and light chain.^[1]^[2] Each paratope is a set of six complementarity-determining regions - three on the light chain and three on the heavy chain - that extend from a fold of anti-parallel beta sheets.^[2] Each arm of the Y-shaped antibody has an identical paratope at the end.^[2]

B-cell receptors include antibodies, so they include paratopes. All of the paratopes on any individual B cell are identical.^[2] The uniqueness of a paratope allows it to bind to only one epitope with high affinity and, as a result, each B cell can only respond to one epitope. The binding of paratopes on B-cell receptors to their specific epitope is a critical step in the adaptive immune response.

Variability

The structure and properties of paratopes differ greatly among species. In jawed vertebrates, V(D)J recombination enables one individual to produce billions of different paratopes.^[3]^[4] However, the number of possible paratopes is limited by the composition of the V, D, and J genes and the structure of the antibody.^[3] In many species, additional mechanisms increase the diversity of possible paratopes. In cows, an extra-long complementarity-determining region is considered to have an essential role in diversifying paratopes.^[3]^[5] Chickens and rabbits use gene conversion to increase the number of possible paratopes.^[3]

References

1 2 3 Lefranc MP (2013). "Paratope". In Dubitzky W, Wolkenhauer O, Cho KH, Yokota H (eds.). Encyclopedia of Systems Biology. New York, NY: Springer. pp. 1632–1633. doi:10.1007/978-1-4419-9863-7_673. ISBN 978-1-4419-9863-7.
1 2 3 4 5 Punt J, Stranford SA, Jones PP, Owen JA (2019). Kuby immunology (Eighth ed.). New York. ISBN 978-1-4641-8978-4. OCLC 1002672752.{{cite book}}: CS1 maint: location missing publisher (link)
1 2 3 4 de los Rios M, Criscitiello MF, Smider VV (August 2015). "Structural and genetic diversity in antibody repertoires from diverse species". Current Opinion in Structural Biology. 33: 27–41. doi:10.1016/j.sbi.2015.06.002. PMC 7039331. PMID 26188469.
↑ Litman GW, Rast JP, Fugmann SD (August 2010). "The origins of vertebrate adaptive immunity". Nature Reviews. Immunology. 10 (8): 543–53. doi:10.1038/nri2807. PMC 2919748. PMID 20651744.
↑ Wang F, Ekiert DC, Ahmad I, Yu W, Zhang Y, Bazirgan O, et al. (June 2013). "Reshaping antibody diversity". Cell. 153 (6): 1379–93. doi:10.1016/j.cell.2013.04.049. PMC 4007204. PMID 23746848.

This immunology article is a stub. You can help Wikipedia by adding missing information.

[:1-1] 1 2 3 Lefranc MP (2013). "Paratope". In Dubitzky W, Wolkenhauer O, Cho KH, Yokota H (eds.). Encyclopedia of Systems Biology. New York, NY: Springer. pp. 1632–1633. doi:10.1007/978-1-4419-9863-7_673. ISBN 978-1-4419-9863-7.

[:0-2] 1 2 3 4 5 Punt J, Stranford SA, Jones PP, Owen JA (2019). Kuby immunology (Eighth ed.). New York. ISBN 978-1-4641-8978-4. OCLC 1002672752.{{cite book}}: CS1 maint: location missing publisher (link)

[:2-3] 1 2 3 4 de los Rios M, Criscitiello MF, Smider VV (August 2015). "Structural and genetic diversity in antibody repertoires from diverse species". Current Opinion in Structural Biology. 33: 27–41. doi:10.1016/j.sbi.2015.06.002. PMC 7039331. PMID 26188469.

[4] Litman GW, Rast JP, Fugmann SD (August 2010). "The origins of vertebrate adaptive immunity". Nature Reviews. Immunology. 10 (8): 543–53. doi:10.1038/nri2807. PMC 2919748. PMID 20651744.

[5] Wang F, Ekiert DC, Ahmad I, Yu W, Zhang Y, Bazirgan O, et al. (June 2013). "Reshaping antibody diversity". Cell. 153 (6): 1379–93. doi:10.1016/j.cell.2013.04.049. PMC 4007204. PMID 23746848.

[1]

[2]

[3]

[4]

[5]