Antibody: Difference between revisions

An '''antibody''' ('''Ab''') is the secreted form of a [[B cell]] receptor; the term '''immunoglobulin''' ('''Ig''') can refer to either the membrane-bound form or the secreted form of the B cell receptor, but they are, broadly speaking, the same protein, and so the terms are often treated as synonymous.<ref name="Rhoades">{{cite book|url=https://archive.org/details/humanphysiologyw00rodn/page/584|title=Human Physiology|vauthors=Rhoades RA, Pflanzer RG|publisher=Thomson Learning|year=2002|isbn=978-0-534-42174-8|edition=5th|page=[https://archive.org/details/humanphysiologyw00rodn/page/584 584]|url-access=registration}}</ref> Antibodies are large, Y-shaped [[protein]]s belonging to the [[immunoglobulin superfamily]] which are used by the [[immune system]] to identify and neutralize foreign objects[[Antigen|antigens]] such as [[pathogenic bacteria|bacteria]] and [[virus]]es, including those that cause disease. Antibodies can recognize virtually any size antigen with diverse chemical compositions from molecules.<ref>{{cite journal |last1=Wilson |first1=Ian A. |last2=Stanfield |first2=Robyn L. |title=50 Years of structural immunology |journal=The Journal of Biological Chemistry |date=3 May 2021 |volume=296 |pages=100745 |doi=10.1016/j.jbc.2021.100745 |doi-access=free |pmid=33957119 |pmc=8163984 |issn=0021-9258 |quote=Antibodies (A–D) can recognize virtually any antigen whether large or small, and which can have diverse chemical compositions from small molecules (A) to carbohydrates to lipids to peptides (B) to proteins (C and D) and combinations thereof.}}</ref> Each antibody recognizes one or more specific [[antigen]]s.<ref name="Janeway5">{{cite book|url=https://archive.org/details/immunobiology00char|title=Immunobiology| vauthors = Janeway C |publisher=Garland Publishing|year=2001|isbn=978-0-8153-3642-6|edition=5th|url-access=registration}}</ref><ref name="pmid8450761">{{cite journal | vauthors = Litman GW, Rast JP, Shamblott MJ, Haire RN, Hulst M, Roess W, Litman RT, Hinds-Frey KR, Zilch A, Amemiya CT | title = Phylogenetic diversification of immunoglobulin genes and the antibody repertoire | journal = Molecular Biology and Evolution | volume = 10 | issue = 1 | pages = 60–72 | date = January 1993 | pmid = 8450761 | doi = 10.1093/oxfordjournals.molbev.a040000 | doi-access = free }}</ref> This termAntigen literally means "antibody generator", as it is the presence of an antigen that drives the formation of an antigen-specific antibody. Each tip of the "Y" of an antibody contains a [[paratope]] that specifically binds to one particular [[epitope]] on an antigen, allowing the two molecules to bind together with precision. Using this mechanism, antibodies can effectively "tag" a [[microbe]] or an infected cell for attack by other parts of the immune system, or can neutralize it directly (for example, by blocking a part of a virus that is essential for its invasion).