Editing T cell (section)

===Innate-like T cells===
'''Innate-like T cells''' or '''unconventional T cells''' represent some subsets of T cells that behave differently in immunity. They trigger rapid immune responses, regardless of the major histocompatibility complex (MHC) expression, unlike their conventional counterparts (CD4 T helper cells and CD8 cytotoxic T cells), which are dependent on the recognition of peptide antigens in the context of the MHC molecule. Overall, there are three large populations of unconventional T cells: NKT cells, MAIT cells, and gammadelta T cells. Now, their functional roles are already being well established in the context of infections and cancer.<ref>{{cite journal|vauthors = Godfrey DI, Uldrich AP, McCluskey J, Rossjohn J, Moody DB|title = The burgeoning family of unconventional T cells|journal = Nature Immunology|volume = 16|issue = 11|pages = 1114–1123|date = November 2015|pmid = 26482978|doi = 10.1038/ni.3298|s2cid = 30992456}}</ref> Furthermore, these T cell subsets are being translated into many therapies against malignancies such as leukemia, for example.<ref>{{cite journal|vauthors = de Araújo ND, Gama FM, de Souza Barros M, Ribeiro TL, Alves FS, Xabregas LA, Tarragô AM, Malheiro A, Costa AG|display-authors = 6|title = Translating Unconventional T Cells and Their Roles in Leukemia Antitumor Immunity|journal = Journal of Immunology Research|volume = 2021|pages = 6633824|date = 2021|pmid = 33506055|pmc = 7808823|doi = 10.1155/2021/6633824|doi-access = free}}</ref>

====Natural killer T cell====
{{Main|Natural killer T cell}}
[[Natural killer T cell]]s (NKT cells – not to be confused with [[natural killer cell]]s of the innate immune system) bridge the [[adaptive immune system]] with the [[innate immune system]]. Unlike conventional T cells that recognize protein peptide antigens presented by [[major histocompatibility complex]] (MHC) molecules, NKT cells recognize glycolipid antigens presented by [[CD1d]]. Once activated, these cells can perform functions ascribed to both helper and cytotoxic T cells: cytokine production and release of cytolytic/cell killing molecules. They are also able to recognize and eliminate some tumor cells and cells infected with herpes viruses.<ref>{{cite journal|vauthors = Mallevaey T, Fontaine J, Breuilh L, Paget C, Castro-Keller A, Vendeville C, Capron M, Leite-de-Moraes M, Trottein F, Faveeuw C|title = Invariant and noninvariant natural killer T cells exert opposite regulatory functions on the immune response during murine schistosomiasis|journal = Infection and Immunity|volume = 75|issue = 5|pages = 2171–80|date = May 2007|pmid = 17353286|pmc = 1865739|doi = 10.1128/IAI.01178-06}}</ref>

====Mucosal associated invariant T cells====
{{main|Mucosal associated invariant T cell}}
Mucosal associated invariant T (MAIT) cells display [[Innate immune system|innate]], effector-like qualities.<ref name=":02">{{cite journal|vauthors = Napier RJ, Adams EJ, Gold MC, Lewinsohn DM|title = The Role of Mucosal Associated Invariant T Cells in Antimicrobial Immunity|journal = Frontiers in Immunology|volume = 6|pages = 344|date = 2015-07-06|pmid = 26217338|pmc = 4492155|doi = 10.3389/fimmu.2015.00344|doi-access = free}}</ref><ref>{{cite journal|vauthors = Gold MC, Lewinsohn DM|title = Mucosal associated invariant T cells and the immune response to infection|journal = Microbes and Infection|volume = 13|issue = 8–9|pages = 742–8|date = August 2011|pmid = 21458588|pmc = 3130845|doi = 10.1016/j.micinf.2011.03.007}}</ref> In humans, MAIT cells are found in the blood, liver, lungs, and [[Mucous membrane|mucosa]], defending against microbial activity and infection.<ref name=":02"/> The [[MHC class I]]-like protein, [[MR1 (gene)|MR1]], is responsible for presenting bacterially-produced [[B vitamins|vitamin B]] metabolites to MAIT cells.<ref name=":4">{{cite journal|vauthors = Eckle SB, Corbett AJ, Keller AN, Chen Z, Godfrey DI, Liu L, Mak JY, Fairlie DP, Rossjohn J, McCluskey J|title = Recognition of Vitamin B Precursors and Byproducts by Mucosal Associated Invariant T Cells|journal = The Journal of Biological Chemistry|volume = 290|issue = 51|pages = 30204–11|date = December 2015|pmid = 26468291|pmc = 4683245|doi = 10.1074/jbc.R115.685990|doi-access = free}}</ref><ref name=":6">{{cite journal|vauthors = Ussher JE, Klenerman P, Willberg CB|title = Mucosal-associated invariant T-cells: new players in anti-bacterial immunity|journal = Frontiers in Immunology|volume = 5|pages = 450|date = 2014-10-08|pmid = 25339949|pmc = 4189401|doi = 10.3389/fimmu.2014.00450|doi-access = free}}</ref><ref name=":12">{{cite journal|vauthors = Howson LJ, Salio M, Cerundolo V|title = MR1-Restricted Mucosal-Associated Invariant T Cells and Their Activation during Infectious Diseases|journal = Frontiers in Immunology|volume = 6|pages = 303|date = 2015-06-16|pmid = 26136743|pmc = 4468870|doi = 10.3389/fimmu.2015.00303|doi-access = free}}</ref> After the presentation of foreign antigen by MR1, MAIT cells secrete pro-inflammatory [[cytokine]]s and are capable of [[Lysis|lysing]] bacterially-infected cells.<ref name=":02"/><ref name=":12"/> MAIT cells can also be activated through MR1-independent signaling.<ref name=":12"/> In addition to possessing innate-like functions, this T cell subset supports the [[Adaptive immune system|adaptive]] immune response and has a memory-like phenotype.<ref name=":02"/> Furthermore, MAIT cells are thought to play a role in [[autoimmune disease]]s, such as [[multiple sclerosis]], arthritis and [[inflammatory bowel disease]],<ref name=":5">{{cite journal|vauthors = Hinks TS|title = Mucosal-associated invariant T cells in autoimmunity, immune-mediated diseases and airways disease|journal = Immunology|volume = 148|issue = 1|pages = 1–12|date = May 2016|pmid = 26778581|pmc = 4819138|doi = 10.1111/imm.12582}}</ref><ref name=":9">{{cite journal|vauthors = Bianchini E, De Biasi S, Simone AM, Ferraro D, Sola P, Cossarizza A, Pinti M|title = Invariant natural killer T cells and mucosal-associated invariant T cells in multiple sclerosis|journal = Immunology Letters|volume = 183|pages = 1–7|date = March 2017|pmid = 28119072|doi = 10.1016/j.imlet.2017.01.009}}</ref> although definitive evidence is yet to be published.<ref>{{cite journal|vauthors = Serriari NE, Eoche M, Lamotte L, Lion J, Fumery M, Marcelo P, Chatelain D, Barre A, Nguyen-Khac E, Lantz O, Dupas JL, Treiner E|title = Innate mucosal-associated invariant T (MAIT) cells are activated in inflammatory bowel diseases|journal = Clinical and Experimental Immunology|volume = 176|issue = 2|pages = 266–74|date = May 2014|pmid = 24450998|pmc = 3992039|doi = 10.1111/cei.12277}}</ref><ref>{{cite journal|vauthors = Huang S, Martin E, Kim S, Yu L, Soudais C, Fremont DH, Lantz O, Hansen TH|title = MR1 antigen presentation to mucosal-associated invariant T cells was highly conserved in evolution|journal = Proceedings of the National Academy of Sciences of the United States of America|volume = 106|issue = 20|pages = 8290–5|date = May 2009|pmid = 19416870|pmc = 2688861|doi = 10.1073/pnas.0903196106|bibcode = 2009PNAS..106.8290H|doi-access = free}}</ref><ref>{{cite journal|vauthors = Chua WJ, Hansen TH|title = Bacteria, mucosal-associated invariant T cells and MR1|journal = Immunology and Cell Biology|volume = 88|issue = 8|pages = 767–9|date = November 2010|pmid = 20733595|doi = 10.1038/icb.2010.104|s2cid = 27717815|doi-access = free}}</ref><ref>{{cite journal|vauthors = Kjer-Nielsen L, Patel O, Corbett AJ, Le Nours J, Meehan B, Liu L, Bhati M, Chen Z, Kostenko L, Reantragoon R, Williamson NA, Purcell AW, Dudek NL, McConville MJ, O'Hair RA, Khairallah GN, Godfrey DI, Fairlie DP, Rossjohn J, McCluskey J|title = MR1 presents microbial vitamin B metabolites to MAIT cells|journal = Nature|volume = 491|issue = 7426|pages = 717–23|date = November 2012|pmid = 23051753|doi = 10.1038/nature11605|bibcode = 2012Natur.491..717K|s2cid = 4419703|url = https://espace.library.uq.edu.au/view/UQ:284808/UQ284808_OA.pdf}}</ref>

====Gamma delta T cells====
{{Main|Gamma delta T cell}}
[[Gamma delta T cell]]s (γδ T cells) represent a small subset of T cells which possess a γδ TCR rather than the αβ TCR on the cell surface. The majority of T cells express αβ TCR chains. This group of T cells is much less common in humans and mice (about 2% of total T cells) and are found mostly in the gut [[mucosa]], within a population of [[intraepithelial lymphocyte]]s. In rabbits, sheep, and chickens, the number of γδ T cells can be as high as 60% of total T cells. The antigenic molecules that activate γδ T cells are still mostly unknown. However, γδ T cells are not MHC-restricted and seem to be able to recognize whole proteins rather than requiring peptides to be presented by MHC molecules on [[antigen presenting cells|APCs]]. Some [[murinae|murine]] γδ T cells recognize MHC class IB molecules. Human γδ T cells that use the Vγ9 and Vδ2 gene fragments constitute the major γδ T cell population in peripheral blood. These cells are unique in that they specifically and rapidly respond to a set of nonpeptidic phosphorylated [[isoprenoid]] precursors, collectively named [[phosphoantigen]]s, which are produced by virtually all living cells. The most common phosphoantigens from animal and human cells (including cancer cells) are [[isopentenyl pyrophosphate]] (IPP) and its isomer [[dimethylallyl pyrophosphate]] (DMPP). Many microbes produce the active compound hydroxy-DMAPP ([[HMB-PP]]) and corresponding mononucleotide conjugates, in addition to IPP and DMAPP. Plant cells produce both types of phosphoantigens. Drugs activating human Vγ9/Vδ2 T cells comprise synthetic phosphoantigens and [[bisphosphonates|aminobisphosphonates]], which upregulate endogenous IPP/DMAPP.