Editing Thymus (section)

==History==
The thymus was known to the [[ancient Greeks]], and its name comes from the Greek word θυμός (''thumos''), meaning "anger",  or in Ancient Greek, "heart, soul, desire, life", possibly because of its location in the chest, near where emotions are subjectively felt;<ref>{{Cite web|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=qumo/s|title=θυμός| first1 = Henry George | last1 = Liddell | first2 = Robert | last2 = Scott | name-list-style = vanc |website=A Greek-English Lexicon|access-date=2019-12-10}}</ref> or else the name comes from the herb ''thyme'' (also in Greek ''θύμος'' or ''θυμάρι''), which became the name for a "warty excrescence", possibly due to its resemblance to a bunch of thyme.<ref>{{Cite web|url=https://www.etymonline.com/word/thymus|title=thymus {{!}} Origin and meaning of thymus by Online Etymology Dictionary|website=www.etymonline.com|language=en|access-date=2019-12-10}}</ref>

[[Galen]] was the first to note that the size of the organ changed over the duration of a person's life.<ref>{{cite journal | vauthors = Nishino M, Ashiku SK, Kocher ON, Thurer RL, Boiselle PM, Hatabu H | title = The thymus: a comprehensive review | journal = Radiographics | volume = 26 | issue = 2 | pages = 335–48 | year = 2006 | pmid = 16549602 | doi = 10.1148/rg.262045213 }}</ref>

In the 19th century, a condition was identified as ''status thymicolymphaticus'' defined by an increase in lymphoid tissue and an enlarged thymus. It was thought to be a cause of [[sudden infant death syndrome]] but is now an obsolete term.<ref>{{cite book|last1=Sapolsky|first1=Robert M. | name-list-style = vanc |author-link=Robert Sapolsky|title=Why zebras don't get ulcers|date=2004|publisher=Henry Hold and Co./Owl Books|location=New York|isbn=978-0805073690|pages=182–185|edition=3rd}}</ref>

The importance of the thymus in the immune system was discovered in 1961 by [[Jacques Miller]], by surgically removing the thymus from one-day-old mice, and observing the subsequent deficiency in a lymphocyte population, subsequently named T cells after the organ of their origin.<ref>{{cite journal | vauthors = Miller JF | title = The discovery of thymus function and of thymus-derived lymphocytes | journal = Immunological Reviews | volume = 185 | issue = 1 | pages = 7–14 | date = July 2002 | pmid = 12190917 | doi = 10.1034/j.1600-065X.2002.18502.x | s2cid = 12108587 }}</ref><ref>{{cite journal | vauthors = Miller JF | title = Events that led to the discovery of T-cell development and function--a personal recollection | journal = Tissue Antigens | volume = 63 | issue = 6 | pages = 509–17 | date = June 2004 | pmid = 15140026 | doi = 10.1111/j.0001-2815.2004.00255.x }}</ref> Until the discovery of its immunological role, the thymus had been dismissed as an "evolutionary accident", without functional importance.<ref name=":0" /> The role the thymus played in ensuring mature T cells tolerated the tissues of the body was uncovered in 1962, with the finding that T cells of a transplanted thymus in mice demonstrated tolerance towards tissues of the donor mouse.<ref name=":0" /> B cells and T cells were identified as different types of lymphocytes in 1968, and the fact that T cells required maturation in the thymus was understood.<ref name=":0" /> The subtypes of T cells (CD8 and CD4) were identified by 1975.<ref name=":0" /> The way that these subclasses of T cells matured – positive selection of cells that functionally bound to MHC receptors – was known by the 1990s.<ref name=":0" /> The important role of the AIRE gene, and the role of negative selection in preventing autoreactive T cells from maturing, was understood by 1994.<ref name=":0" />

Recently, advances in [[immunology]] have allowed the function of the thymus in T-cell maturation to be more fully understood.<ref name=":0">{{cite journal | vauthors = Miller JF | title = The golden anniversary of the thymus | journal = Nature Reviews. Immunology | volume = 11 | issue = 7 | pages = 489–95 | date = May 2011 | pmid = 21617694 | doi = 10.1038/nri2993 | s2cid = 21191923 }}</ref>