Editing Peyer's patch

{{Short description|Lymphatic tissue in the lower small intestine}}
{{Infobox lymph
| Name        = Peyer's patch
| Latin       = noduli lymphoidei aggregati
| Image       = Peyer's patch (improved color).jpg
| Caption     = Cross section of [[ileum]] with a Peyer's patch circled
| Image2      =
| Caption2    =
| Precursor   =
}}
'''Peyer's patches''' or '''aggregated lymphoid nodules''' are organized [[lymphoid follicle]]s, named after the 17th-century Swiss anatomist [[Johann Conrad Peyer]].<ref name = "Peyer" >{{cite book |last1=Peyer |first1=Johann Conrad |title=Exercitatio Anatomico-Medica de Glandulis Intestinorum, Earumque Usu et Affectionibus |trans-title=Anatomical-medical essay on the intestinal glands, and their function and diseases |date=1677 |publisher=Onophrius à Waldkirch |location=Schaffhausen, Switzerland |language=Latin}}
*  Reprinted as: {{cite book |last1=Peyer |first1=Johann Conrad |title=Exercitatio Anatomico-Medica de Glandulis Intestinorum, Earumque Usu et Affectionibus |date=1681 |publisher=Henrik Wetstein |location=Amsterdam, Netherlands |url=https://books.google.com/books?id=AiM_AAAAcAAJ&pg=PP7 |language=Latin}}
*  Peyer referred to Peyer's patches as ''plexus'' or ''agmina glandularum'' (clusters of glands).  From (Peyer, 1681), p. 7: ''"Tenui a perfectiorum animalium Intestina accuratius perlustranti, crebra hinc inde, variis intervallis, corpusculorum glandulosorum Agmina sive Plexus se produnt, diversae Magnitudinis atque Figurae."'' (I knew from careful study of more advanced animals, the intestines bear — often here and there, at various intervals — clusters of glandular small bodies or "plexuses" of diverse size and shape.) From p. 15: ''"(has Plexus seu agmina Glandularum voco)"'' (I call them "plexuses" or clusters of glands)  He described their appearance.  From p. 8:  ''"Horum vero Plexuum facies modo in orbem concinnata; modo in Ovi aut Olivae oblongam, aliamve angulosam ac magis anomalam disposita figuram cernitur."'' (But the configurations of these "plexuses" are arranged at one time in a circle; at another time, it is seen in an egg [shape] or an oblong olive [shape] or other faceted and more irregularly arranged shape.)  Drawings of Peyer's patches appear after pages 22 and 24.</ref>  They are an important part of [[gut associated lymphoid tissue]] usually found in humans in the lowest portion of the [[small intestine]], mainly in the distal [[jejunum]] and the [[ileum]], but also could be detected in the [[duodenum]].<ref name="Cornes J S 1965">{{cite journal | vauthors = Zijlstra M, Auchincloss H, Loring JM, Chase CM, Russell PS, Jaenisch R | title = Skin graft rejection by beta 2-microglobulin-deficient mice | journal = The Journal of Experimental Medicine | volume = 175 | issue = 4 | pages = 885–93 | date = April 1992 | pmc = 1552287 | doi = 10.1136/gut.6.3.225 | pmid = 18668776 }}</ref>

== History == 

Peyer's patches had been observed and described by several anatomists during the 17th century,<ref>{{cite book |last1=Haller |first1=Albrecht von |title=Elementa Physiologiae corporis humani |trans-title=Elements of the physiology of the human body |date=1765 |publisher=Societas Typographica |location=Bern, Switzerland |volume=7 |page=35 |url=https://books.google.com/books?id=E3lIAAAAYAAJ&pg=PA35 |language=Latin}}  Anatomists who mentioned Peyer's patches included:
*  Johann Theodor Schenck (1619–1671):  {{cite book |last1=Schenck |first1=Johann Theodor |title=Exercitationes Anatomicæ ad Usum Medicum Accommodatæ |trans-title=Anatomical Exercises Suited to Medical Practice |date=1672 |publisher=Johann Ludwig Neuenhahn |location=Jena, (Germany) |page=334 |url=https://books.google.com/books?id=jRxmAAAAcAAJ&pg=PA334 |language=Latin}} Schenk thought that intestinal worms resided in Peyer's patches and that the orifices of the patches were the worms' mouths.  From p. 334:  ''"In canibus saepissime observavi non ad ventriculum … a praeter labente chylo sibi conveniens allicerent."''  (In dogs, I very often noticed — not only near the stomach but also on the walls of their small intestines — flesh-colored or  glandular blisters, [appearing] to swim one after another, [in] which, when we dissected [them], I observed some smooth reddish worms [''vermium''] living there in clusters [with] their heads facing towards the cavity of the intestines, in which part there were glands with orifices, [but] reversed, so that from there they obtained, from the chyle flowing past, nourishment [that was] suitable for them.)
*  Jeremias Loss (1643–1684):  {{cite book |last1=Loss |first1=Jeremias |title=Dissertatio Medica de Glandulis in Genere |trans-title=Medical Discourse on Glands in [Various] Species |date=1683 |publisher=Martin Schultz |location=Wittenberg, (Germany) |page=12 |url=https://wellcomecollection.org/works/evskthgv/items?canvas=14 |language=Latin}}  On page 12, Loss states that some glands are located "''inter Membranas viscerum quorundam''" (between the membranes of certain internal organs) "'' … prout id in Glandulis Intestinorum satis manifestum est.''" (as it is quite clear in the glands of the intestines), where "''In Intestinis ita congregantur, interdum pauciores, interdum plures, ut areolas quasdam constituant: … ''" (in the intestines there are thus gathered sometimes fewer [glands], sometimes more [glands], so that they form certain round patches.)      
*  Johannes Nicolaus Pechlin (1646–1706):  {{cite book |last1=Pechlin |first1=Johannes Nicolaus |title=De Purgantium Medicamentorum Facultatibus |trans-title=On the Means of Medicinal Purges |date=1672 |publisher=Daniel, Abraham, and Adrian à Gaasbeek |location=Leiden and Amsterdam, Netherlands |page=510 |url=https://books.google.com/books?id=POBbAAAAcAAJ&pg=PA510 |language=Latin}}  From p. 510:  ''" … ego tenuium glandularum glomeratum agmen esse ratus, … "'' (… I considered the heaped cluster of fine glands, … )
*  Martin Lister (ca. 1638–1712):  {{cite journal |last1=Lister |first1=Martin |title=A letter of Mr Lister dated May 21. 1673. in York, partly taking notice of the foregoing intimations, partly communicating some anatomical observations and experiments concerning the unalterable character of the whiteness of the chyle within the lacteous veins; together with divers particulars observed in the guts, especially several sorts of worms found in them. |journal=Philosophical Transactions of the Royal Society of London |date=23 June 1673 |volume=8 |issue=95 |pages=6060–6065 |doi=10.1098/rstl.1673.0026 |bibcode=1673RSPT....8.6060L |url=https://royalsocietypublishing.org/doi/epdf/10.1098/rstl.1673.0026}}  From p. 6062:  "As 1. ''Glandulae miliares'' of the small Guts, which may also in some Animals be well call'd ''fragi-formes'', from the figure of the one half of a ''Strawberry'', and which yet I take to be ''Excretive'' glanduls, because ''Conglomerate''." 
*  Nehemiah Grew (1641–1712):  {{cite book |last1=Grew |first1=Nehemiah |title=The Comparative Anatomy of Stomachs and Guts Begun. Being Several Lectures Read before the Royal Society. In the Year, 1676. |date=1681 |publisher=Self-published |location=London, England |page=3 |url=https://quod.lib.umich.edu/e/eebo2/B03528.0001.001/1:3?rgn=div1;view=fulltext}}  Grew called Peyer's patches ''pancreas intestinale''.</ref> but in 1677 Swiss anatomist Johann Conrad Peyer (1653–1712) described the patches so clearly that they were eventually named after him.<ref name = "Peyer" /><ref>There were many earlier names for Peyer's patches:
*  {{cite book |editor1-last=Todd |editor1-first=Robert Bentley |title=The Cyclopædia of Anatomy and Physiology |date=1859 |publisher=Longman, Brown, Green, Longmans, & Roberts |location=London, England |volume=5 |page=356 footnote |url=https://books.google.com/books?id=wjoAAAAAQAAJ&pg=RA2-PA356}}
*  {{cite book |last1=Leidy |first1=Joseph |title=An Elementary Treatise on Human Anatomy |date=1861 |publisher=J.B. Lippincott & Co. |location=Philadelphia, Pennsylvania, USA |page=313 footnote |url=https://books.google.com/books?id=b4YZAAAAYAAJ&pg=PA313}}</ref>  However, Peyer believed they were glands that secreted something into the small intestine to facilitate digestion. It was not until 1850 that the Swiss physician Rudolph Oskar Ziegler (1828–1881) suggested, after careful microscopic examination, that Peyer's patches were actually lymph glands.<ref>Ziegler, Rudolph Oskar (1850) [https://archive.org/details/b22355972 ''Ueber die solitären und Peyerschen Follikel : Inaugural-Abhandlung, der medicinischen Facultät der Julius-Maximilians-Universität zu Würzburg vorgelegt''] [On solitary and Peyer's follicles: Inaugural treatise, submitted to the medical faculty of the Julius-Maximilians-University of Würzburg] (in German) Würzburg, (Germany):  Friederich Ernst Thein.  From  p. 37:  ''"Ebensogross, wo nicht grösser ist die Aehnlichkeit der sogenannten Peyer'schen Drüsen und der Lymphdrüsen."'' (Just as great, if not greater, is the resemblance between the so-called Peyer's glands and the lymph glands.)  From  p. 38: ''" … ja, man könnte selbst versucht sein, die letzteren für nichts als eine Art von zwischen den Wänden der Darmsschleimhaut eingebetteten Lymphdrüsen zu halten."'' ( … indeed, one could even be tempted to regard the latter [i.e., the Peyer's patches] as nothing but some type of lymph glands [which are] embedded between the walls of the intestinal mucosa.)</ref>

== Structure ==
Peyer's patches are observable as elongated thickenings of the [[intestinal mucosa]] measuring a few centimeters in length. About 100 are found in humans. Microscopically, Peyer's patches appear as oval or round lymphoid follicles (similar to [[lymph nodes]]) located in the [[mucosa]] layer of the [[ileum]] and extend into the [[submucosa]] layer.
The number of Peyer's patches peaks at age 15–25 and then declines during adulthood.<ref name="Cornes J S 1965"/>
In the distal ileum, they are numerous and they form a lymphoid ring. At least 46% of Peyer's patches are concentrated in the distal 25&nbsp;cm of ileum in humans. It is important to note that there are large variations in size, shape, and distribution of Peyer's patches from one individual to another one.<ref>{{cite journal | vauthors = Van Kruiningen HJ, West AB, Freda BJ, Holmes KA | title = Distribution of Peyer's patches in the distal ileum | journal = Inflammatory Bowel Diseases | volume = 8 | issue = 3 | pages = 180–5 | date = May 2002 | pmid = 11979138 | doi = 10.1097/00054725-200205000-00004 | s2cid = 22514793 | doi-access = free }}</ref>
In adults, B lymphocytes are seen to dominate the follicles' germinal centers.  [[T lymphocytes]] are found in the zones between follicles. Among the mononuclear cells, CD4+/CD25+ (10%) cells and CD8+/CD25+ (5%) cells are more abundant in Peyer's patches than in the peripheral blood.<ref name="pmid21188221">{{cite journal | vauthors = Jung C, Hugot JP, Barreau F | title = Peyer's Patches: The Immune Sensors of the Intestine | journal = International Journal of Inflammation | volume = 2010 | pages = 823710 | date = September 2010 | pmid = 21188221 | pmc = 3004000 | doi = 10.4061/2010/823710 | doi-access = free }}</ref>

Peyer's patches are characterized by the follicle-associated epithelium (FAE), which covers all lymphoid follicles.<ref name="ReferenceA">{{cite journal | vauthors = Owen RL, Jones AL | title = Epithelial cell specialization within human Peyer's patches: an ultrastructural study of intestinal lymphoid follicles | journal = Gastroenterology | volume = 66 | issue = 2 | pages = 189–203 | date = February 1974 | pmid = 4810912 | doi=10.1016/s0016-5085(74)80102-2| doi-access = free }}</ref> FAE differs from typical small [[intestinal villus]] epithelium: it has fewer [[goblet cells]]<ref>{{cite journal | vauthors = Onori P, Franchitto A, Sferra R, Vetuschi A, Gaudio E | title = Peyer's patches epithelium in the rat: a morphological, immunohistochemical, and morphometrical study | journal = Digestive Diseases and Sciences | volume = 46 | issue = 5 | pages = 1095–104 | date = May 2001 | pmid = 11341655 | doi=10.1023/a:1010778532240| s2cid = 34204173 }}</ref> therefore mucus layer is thinner,<ref>{{cite journal | vauthors = Ermund A, Gustafsson JK, Hansson GC, Keita AV | title = Mucus properties and goblet cell quantification in mouse, rat and human ileal Peyer's patches | journal = PLOS ONE | volume = 8 | issue = 12 | pages = e83688 | year = 2013 | pmid = 24358305 | doi = 10.1371/journal.pone.0083688 | pmc = 3865249 | bibcode = 2013PLoSO...883688E | doi-access = free }}</ref> and it is also characterized by the presence of specialized M cells or [[microfold cells]], which provide uptake and transport of antigens from lumen.<ref name="ReferenceA"/> Moreover, [[basal lamina]] of follicle-associated epithelium is more porous compared to intestinal villus.<ref>{{cite journal | vauthors = Takeuchi T, Gonda T | title = Distribution of the pores of epithelial basement membrane in the rat small intestine | journal = The Journal of Veterinary Medical Science | volume = 66 | issue = 6 | pages = 695–700 | date = June 2004 | pmid = 15240945 | doi=10.1292/jvms.66.695| doi-access = free }}</ref> Finally, follicle-associated epithelium is less permeable for ions and macromolecules, basically due to higher expression of [[tight junction]] proteins.<ref>{{cite journal | vauthors = Markov AG, Falchuk EL, Kruglova NM, Radloff J, Amasheh S | title = Claudin expression in follicle-associated epithelium of rat Peyer's patches defines a major restriction of the paracellular pathway | journal = Acta Physiologica | volume = 216 | issue = 1 | pages = 112–9 | date = January 2016 | pmid = 26228735 | doi = 10.1111/apha.12559 | hdl = 11701/6438 | s2cid = 13389571 | hdl-access = free }}</ref>

== Function ==
Because the [[Lumen (anatomy)|lumen]] of the [[gastrointestinal tract]] is exposed to the external environment, much of it is populated with potentially [[pathogen]]ic [[microorganism]]s. Peyer's patches thus establish their importance in the immune surveillance of the intestinal lumen and in facilitating production of the immune response within the [[mucosa]].

Pathogenic microorganisms and other [[antigen]]s entering the intestinal tract encounter [[macrophages]], [[dendritic cell]]s, [[B-cells|B-lymphocytes]], and [[T-lymphocytes]] found in Peyer's patches and other sites of [[gut-associated lymphoid tissue]] (GALT). Peyer's patches thus act for the gastrointestinal system much as the [[tonsil]]s act for the [[respiratory system]], trapping foreign particles, surveilling them, and destroying them. Peyer's patches have adaptive immune capabilities through inducing selective apoptosis of B cells due [[CD122]]-targeted [[Interleukin 2|interleukin-2]] (IL-2) signaling. Additionally, the B cell population can be restored. <ref>{{Cite journal |last1=Singh |first1=Ayushi |last2=Dhume |first2=Kunal |last3=Tejero |first3=Joanne D. |last4=Strutt |first4=Tara M. |last5=McKinstry |first5=K. Kai |date=2020-07-29 |title=CD122-targetted IL-2 signals cause acute and selective apoptosis of B cells in Peyer's Patches |journal=Scientific Reports |language=en |volume=10 |issue=1 |pages=12668 |doi=10.1038/s41598-020-69632-5 |issn=2045-2322 |pmc=7391758 |pmid=32728053|bibcode=2020NatSR..1012668S }}</ref>

Peyer's patches are covered by a special follicle-associated epithelium that contains specialized cells called microfold cells ([[Microfold cell|M cells]]) which sample antigen directly from the lumen and deliver it to [[antigen-presenting cells]] (located in a unique pocket-like structure on their [[Epithelial polarity#Basolateral membranes|basolateral side]]). Dendritic cells and macrophages can also directly sample the lumen by extending dendrites through transcellular M cell-specific pores.<ref>{{cite journal | vauthors = Lelouard H, Fallet M, de Bovis B, Méresse S, Gorvel JP | title = Peyer's patch dendritic cells sample antigens by extending dendrites through M cell-specific transcellular pores | journal = Gastroenterology | volume = 142 | issue = 3 | pages = 592–601.e3 | date = March 2012 | pmid = 22155637 | doi = 10.1053/j.gastro.2011.11.039 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Bonnardel J, Da Silva C, Henri S, Tamoutounour S, Chasson L, Montañana-Sanchis F, Gorvel JP, Lelouard H | title = Innate and adaptive immune functions of peyer's patch monocyte-derived cells | journal = Cell Reports | volume = 11 | issue = 5 | pages = 770–84 | date = May 2015 | pmid = 25921539 | doi = 10.1016/j.celrep.2015.03.067 | doi-access = free | url = https://amu.hal.science/hal-01212685/file/1-s2.0-S2211124715003587-main.pdf }}</ref> At the same time the paracellular pathway of follicle-associated epithelium is closed tightly to prevent penetration of antigens and continuous contact with immune cells.<ref>{{cite journal | vauthors = Diener M | title = Roadblock for antigens--take a detour via M cells | journal = Acta Physiologica | volume = 216 | issue = 1 | pages = 13–4 | date = January 2016 | pmid = 26335934 | doi = 10.1111/apha.12595 | doi-access = free }}</ref> [[T cells]], [[B-cell]]s and memory cells are stimulated upon encountering [[antigen]] in Peyer's patches. These cells then pass to the [[mesenteric lymph nodes]] where the immune response is amplified. Activated lymphocytes pass into the blood stream via the [[thoracic duct]] and travel to the gut where they carry out their final effector functions. The maturation of B-lymphocytes takes place in the Peyer's patch.

==Clinical significance==
Although important in the immune response, excessive growth of lymphoid tissue in Peyer's patches is pathologic, as [[Organ hypertrophy|hypertrophy]] of Peyer's patches has been closely associated with idiopathic [[intussusception (medical disorder)|intussusception]].

Having too many or larger than normal Peyer's patches is associated with an increased risk of [[prion disease]]s, and [[intussusception (medical disorder)|intussusception]] in children. A history of viral illness is a risk factor for enlarged or inflamed Peyer's patches.<ref>{{Cite book |last=MD |first=Steven M. Fiser |title=The ABSITE Review |date=2022-08-30 |publisher=LWW |isbn=978-1-9751-9029-3 |edition=7th |language=English}}</ref>

''[[Salmonella|Salmonella typhi]]'' and [[poliovirus]] also target this section of the intestine.<ref name=BMJ />

Disturbances in the gut microbiota and immune regulation within Peyer's patches are implicated in the pathogenesis of autoimmune diseases, such as Crohn's disease, where chronic inflammation can arise due to overactive immune responses.<ref name=C/> As Peyer's patches are packed with immune cells and produce protective proteins such as secretory IgA to maintain gut balance, their dysfunction can trigger inappropriate immune responses, driving the inflammation and tissue damage characteristic of autoimmune diseases.<ref>{{Cite journal |last1=Abo-Shaban |first1=T. |last2=Sharna |first2=S. S. |last3=Hosie |first3=S. |last4=Lee |first4=C. Y. Q. |last5=Balasuriya |first5=G. K. |last6=McKeown |first6=S. J. |last7=Franks |first7=A. E. |last8=Hill-Yardin |first8=E. L. |date=2023-03-01 |title=Issues for patchy tissues: defining roles for gut-associated lymphoid tissue in neurodevelopment and disease |journal=Journal of Neural Transmission |language=en |volume=130 |issue=3 |pages=269–280 |doi=10.1007/s00702-022-02561-x |issn=1435-1463 |pmc=10033573 |pmid=36309872}}</ref>

==See also==
{{Portal|Medicine}}
*[[Influenza]]
*[[Lung cancer]]

== References ==
{{Commons category|Peyer's patches}}{{clear}}
{{Reflist|refs=


<ref name=BMJ>
{{Citation
| last1      = Pascall
| first1     = C R
| last2     = Stearn
| first2    = E J
| last3     = Mosley
| first3    = J G
| title     = Short Reports
| newspaper = [[BMJ|British Medical Journal]]
| pages     = 26
| date      = 1980-07-05
| pmc       = 1713722
| quote     = Unlike S hadar peritonitis, S typhi peritonitis is due to perforation of Peyer's patches.
| pmid      = 7407483
| volume=281
| issue = 6232
| doi = 10.1136/bmj.281.6232.26-a

}}
</ref>
<ref name="C">{{cite journal |last1=Biskou |first1=Olga |last2=Meira de-Faria |first2=Felipe |last3=Walter |first3=Susanna M. |last4=Winberg |first4=Martin E. |last5=Haapaniemi |first5=Staffan |last6=Myrelid |first6=Pär |last7=Söderholm |first7=Johan D. |last8=Keita |first8=Åsa V. |title=Increased Numbers of Enteric Glial Cells in the Peyer's Patches and Enhanced Intestinal Permeability by Glial Cell Mediators in Patients with Ileal Crohn's Disease |journal=Cells |date=January 2022 |volume=11 |issue=3 |pages=335 |doi=10.3390/cells11030335 |doi-access=free |pmid=35159145 |pmc=8833935 |language=en |issn=2073-4409}}</ref>

}}

==External links==
{{Spoken Wikipedia|Peyer's_patch.ogg|date=2019-7-30}}
{{Lymphatic_system}}
{{Digestive tract}}
{{Authority control}}

{{DEFAULTSORT:Peyer's Patch}}
[[Category:Lymphatic system]]
[[Category:Lymphatic tissue]]
[[Category:Small intestine]]