Editing Dendritic cell

{{Short description|Accessory cell of the mammalian immune system}}
{{about|the immune cell|component of the [[neuron]]|dendrite}}
{{Use dmy dates|date=March 2020}}
{{Infobox anatomy
| Name        = Dendritic cell
| Latin       = cellula dendritiformis
| Image       = Dendritic cells.jpg
| Caption     = Dendritic cells in skin
| Width       = 
| Image2      = Dendritic cell revealed.jpg
| Caption2    = Artistic rendering of the surface of a human dendritic cell illustrating sheet-like processes that fold back onto the membrane surface. Some researchers believe that these sheets, when exposed to [[HIV]], entrap viruses in the vicinity and focus them to contact zones with [[T cell]]s targeted for infection. These studies were carried out using [[Ion-abrasion SEM|ion abrasion scanning electron microscopy]].
| Precursor   = 
| System      = [[Immune system]]

| Artery      = 
| Vein        = 
| Nerve       = 
| Lymph       = 
}}
A '''dendritic cell''' ('''DC''')  is an [[antigen-presenting cell]] (also known as an ''accessory cell'') of the [[mammal]]ian [[immune system]]. A DC's main function is to process [[antigen]] material and [[Antigen presentation|present]] it on the cell surface to the [[T cell]]s of the immune system. They act as messengers between the [[Innate immune system|innate]] and [[adaptive immune system]]s.<ref name="Monga">{{cite journal | vauthors = Monga I, Kaur K, Dhanda S| title = Revisiting hematopoiesis: applications of the bulk and single-cell transcriptomics dissecting transcriptional heterogeneity in hematopoietic stem cells | journal = Briefings in Functional Genomics | volume = 21 | issue = 3 | pages = 159–176 | date = March 2022 | pmid = 35265979 | doi = 10.1093/bfgp/elac002}}</ref>

Dendritic cells are present in tissues that are in contact with the body's external environment, such as the [[skin]], and the inner lining of the [[nose]], [[lungs]], [[stomach]] and [[intestine]]s. They can also be found in an immature and mature state in the [[blood]].  Once activated, they migrate to the [[lymph node]]s, where they interact with [[T cell]]s and [[B cell]]s to initiate and shape the adaptive immune response.  At certain development stages they grow branched projections, the ''[[Dendrite (non-neuronal)|dendrites]],'' that give the cell its name (δένδρον or déndron being Greek for 'tree'). While similar in appearance to the dendrites of [[neuron]]s, these are structures distinct from them. Immature dendritic cells are also called '''veiled cells''', as they possess large cytoplasmic 'veils' rather than dendrites.{{Citation needed | date = October 2021 | reason = This seems counterintuitive.  Shouldn't the veils be outside the cells as well?}}

==History==
Dendritic cells were first described by [[Paul Langerhans]] (hence ''Langerhans cells'') in the late nineteenth century. The term ''dendritic cells'' was coined in 1973 by [[Ralph M. Steinman]] and [[Zanvil A. Cohn]].<ref name=Steinman>{{cite journal | doi=10.1084/jem.137.5.1142 |pmc=2139237|year=1973|last1=Steinman|first1=R. M.|title=Identification of a Novel Cell Type in Peripheral Lymphoid Organs of Mice : I. Morphology, Quantitation, Tissue Distribution|journal=The Journal of Experimental Medicine|volume=137|issue=5|pages=1142–1162|last2=Cohn|first2=Z. A.|pmid=4573839}}</ref> For discovering the central role of dendritic cells in the adaptive immune response,<ref name="pmid9521319">{{cite journal |vauthors=Banchereau J, Steinman RM|author-link2=Jacques Banchereau |title=Dendritic cells and the control of immunity |journal=Nature |volume=392 |issue=6673 |pages=245–52 |date=March 1998 |pmid=9521319 |doi=10.1038/32588 |bibcode=1998Natur.392..245B |s2cid=4388748 }}</ref> Steinman was awarded the [[Albert Lasker Award for Basic Medical Research]] in 2007<ref name="Lasker2007">{{cite web |url=http://www.laskerfoundation.org/awards/2007basic.htm |title=The Lasker Foundation – 2007 Awards |access-date=2010-11-27}}</ref> and the [[Nobel Prize in Physiology or Medicine]] in 2011.<ref name="Nobel2011">{{cite web |url=https://www.nobelprize.org/nobel_prizes/medicine/laureates/2011/# |title=Nobel Prize in Physiology or Medicine for 2011}}</ref>

==Types==
The [[Morphology (biology)|morphology]] of dendritic cells results in a very large surface-to-volume ratio.  That is, the dendritic cell has a very large surface area compared to the overall cell volume.

===''In vivo'' – primate===
{{main|Plasmacytoid dendritic cell}}
The most common division of dendritic cells is '''conventional dendritic cells''' (a.k.a. '''myeloid dendritic cells''') vs. [[plasmacytoid dendritic cell]] (most likely of [[Lymphopoiesis#Lymphopoiesis for dendritic cells|lymphoid]] lineage) as described in the table below:

{| class="wikitable"
!width=30%| Name 
!width=30%| Description 
!width=25%| Secretion
!width=15%| [[Toll-like receptor]]s <ref>{{cite journal |vauthors=Sallusto F, Lanzavecchia A |title=The instructive role of dendritic cells on T-cell responses |journal=Arthritis Res. |volume=4 |issue= Suppl 3|pages=S127–32 |year=2002 |pmid=12110131 |doi=10.1186/ar567 |pmc=3240143 |doi-access=free }}</ref>
|-
| Conventional dendritic cell (cDC)<br>(previously called ''myeloid dendritic cell'' (mDC)) 
|| Most similar to [[monocyte]]s. mDC are made up of at least two subsets:
# cDC-1, which is a major stimulator of cytotoxic T cells
#cDC-2, which stimulates helper T cells
|| [[Interleukin 12]] (IL-12), [[Interleukin 6]] (IL-6), TNF, chemokines 
|| [[TLR 2]], [[TLR 4]]
|-
|| Plasmacytoid dendritic cell (pDC) 
|| Look like [[plasma cell]]s, but have certain characteristics similar to myeloid dendritic cells.<ref>{{cite journal |vauthors=McKenna K, Beignon A, Bhardwaj N |title=Plasmacytoid Dendritic Cells: Linking Innate and Adaptive Immunity |journal=[[Journal of Virology|J. Virol.]] |volume=79 |issue=1 |pages=17–27 |year=2005 |pmid=15596797 |doi=10.1128/JVI.79.1.17-27.2005 |pmc=538703}}</ref>   
|| Can produce high amounts of [[interferon|interferon-α]]<ref name="pmid12953097">{{cite journal  |vauthors=Vanbervliet B, Bendriss-Vermare N, Massacrier C, etal |title=The Inducible CXCR3 Ligands Control Plasmacytoid Dendritic Cell Responsiveness to the Constitutive Chemokine Stromal Cell–derived Factor 1 (SDF-1)/CXCL12 |journal=J. Exp. Med. |volume=198 |issue=5 |pages=823–30 |date=September 2003 |pmid=12953097 |pmc=2194187 |doi=10.1084/jem.20020437 }}</ref> and were previously called ''interferon-producing cells''.<ref>{{cite journal |author=Liu YJ |title=IPC: professional type 1 interferon-producing cells and plasmacytoid dendritic cell precursors |journal=Annu. Rev. Immunol. |volume=23 |issue= 1|pages=275–306 |year=2005 |pmid=15771572 |doi=10.1146/annurev.immunol.23.021704.115633}}</ref> || [[TLR 7]], [[TLR 9]]
|}

The markers [[BDCA-2]], [[BDCA-3]], and [[BDCA-4]] can be used to discriminate among the types.<ref>{{cite journal |vauthors=Dzionek A, Fuchs A, Schmidt P, Cremer S, Zysk M, Miltenyi S, Buck D, Schmitz J |title=BDCA-2, BDCA-3, and BDCA-4: three markers for distinct subsets of dendritic cells in human peripheral blood |journal=J Immunol |volume=165 |issue=11 |pages=6037–46 |year=2000 |pmid=11086035 |url=http://www.jimmunol.org/cgi/reprint/165/11/6037.pdf |doi=10.4049/jimmunol.165.11.6037|s2cid=22459468 |doi-access=free }}</ref>

[[File:Centrocyte, centroblast and follicular dendritic cell in a follicular lymphoma.jpg|thumb|Histologic comparison of cell types in a [[germinal center]], including follicular dendritic cells, H&E stain:<br>- '''[[Centrocyte]]s''' are small to medium size with angulated, elongated, cleaved, or twisted nuclei.<br>- '''[[Centroblast]]s''' are larger cells containing vesicular nuclei with one to three basophilic nucleoli apposing the nuclear membrane.<br>- '''[[Follicular dendritic cell]]s''' have round nuclei, centrally located nucleoli, bland and dispersed chromatin, and flattening of adjacent nuclear membrane.]]

Lymphoid and myeloid DCs evolve from lymphoid and myeloid precursors, respectively, and thus are of [[hematopoietic]] origin. By contrast, [[follicular dendritic cells]] (FDC) are probably of [[mesenchymal]] rather than [[hematopoietic]] origin and do not express [[MHC class II]], but are so named because they are located in lymphoid follicles and have long "dendritic" processes.

===In blood===
The blood DCs are typically identified and enumerated in [[flow cytometry]]. Three types of DCs have been defined in human blood: the CD1c+ myeloid DCs, the [[CD141]]+ myeloid DCs and the [[CD303]]+ plasmacytoid DCs. This represents the nomenclature proposed by the nomenclature committee of the [[International Union of Immunological Societies]].<ref>{{Cite journal | doi = 10.1182/blood-2010-02-258558 | pmid=20628149| year=2010| last1=Ziegler-Heitbrock| first1=L| title=Nomenclature of monocytes and dendritic cells in blood| journal=Blood| volume=116| issue=16| pages=e74–80| last2=Ancuta| first2=P| last3=Crowe| first3=S| last4=Dalod| first4=M| last5=Grau| first5=V| last6=Hart| first6=D. N.| last7=Leenen| first7=P. J.| last8=Liu| first8=Y. J.| last9=MacPherson| first9=G| last10=Randolph| first10=G. J.| last11=Scherberich| first11=J| last12=Schmitz| first12=J| last13=Shortman| first13=K| last14=Sozzani| first14=S| last15=Strobl| first15=H| last16=Zembala| first16=M| last17=Austyn| first17=J. M.| last18=Lutz| first18=M. B.| hdl=11379/41075| s2cid=1570404| url=https://iris.unibs.it/bitstream/11379/41075/1/Ziegler%20Blood%202010.pdf| hdl-access=free}}</ref>
Dendritic cells that circulate in blood do not have all the typical features of their counterparts in tissue, i.e. they are less mature and have no dendrites. Still, they can perform complex functions including chemokine-production (in CD1c+ myeloid DCs), [[cross-presentation]] (in CD141+ myeloid DCs), and IFNalpha production (in CD303+ plasmacytoid DCs).

===''In vitro''===
In some respects, dendritic cells cultured [[in vitro]] do not show the same behaviour or capability as dendritic cells isolated ''ex vivo''. Nonetheless, they are often used for research as they are still much more readily available than genuine DCs.

* Mo-DC or MDDC refers to cells matured from [[monocyte]]s.<ref>{{cite journal |vauthors=Ohgimoto K, Ohgimoto S, Ihara T, Mizuta H, Ishido S, Ayata M, Ogura H, Hotta H |title=Difference in production of infectious wild-type measles and vaccine viruses in monocyte-derived dendritic cells |journal=Virus Res |volume=123 |issue=1 |pages=1–8 |year=2007 |pmid=16959355 |doi=10.1016/j.virusres.2006.07.006}}</ref>
* HP-DC refers to cells derived from [[Pluripotential hemopoietic stem cell|hematopoietic progenitor cells]].

==Development and life cycle==

===Formation of immature cells and their maturation===
[[File:Immune_Cells_Development.pdf|thumb|400px|Diagram of hematopoiesis from HSC, showing a separate dendritic cell lineage via CDP (Common Dendritic-cell Progenitor).]]
Dendritic cells are derived from [[hematopoietic stem cells|hematopoietic bone marrow progenitor cells]] (HSC). These progenitor cells initially transform into immature dendritic cells.  These cells are characterized by high endocytic activity and low T-cell activation potential.  Immature dendritic cells constantly sample the surrounding environment for pathogens such as [[virus (biology)|viruses]] and [[bacteria]]. This is done through [[pattern recognition receptors]] (PRRs) such as the [[toll-like receptor]]s (TLRs).  TLRs recognize specific chemical signatures found on subsets of pathogens. Immature dendritic cells may also [[phagocytosis|phagocytose]] small quantities of membrane from live own cells, in a process called nibbling.  Once they have come into contact with a presentable antigen, they become activated into mature dendritic cells and begin to migrate to a [[lymph node]].  Immature dendritic cells phagocytose pathogens and degrade their [[protein]]s into small pieces and upon maturation present those fragments at their cell surface using [[major histocompatibility complex|MHC]] molecules.  Simultaneously, they upregulate cell-surface receptors that act as [[co-stimulation|co-receptors]] in T-cell activation such as [[CD80]] (B7.1), [[CD86]] (B7.2), and [[CD40]] greatly enhancing their ability to activate T-cells.  They also upregulate [[CC chemokine receptors#CCR7|CCR7]], a chemotactic receptor that induces the dendritic cell to travel through the [[blood]] stream to the [[spleen]] or through the [[lymphatic system]] to a [[lymph node]]. Here they act as [[antigen-presenting cell]]s: they activate [[helper T-cell]]s and [[killer T-cell]]s as well as [[B-cell]]s by presenting them with antigens derived from the pathogen, alongside non-antigen specific costimulatory signals. Dendritic cells can also induce T-cell tolerance (unresponsiveness). Certain C-type lectin receptors (CLRs) on the surface of dendritic cells, some functioning as PRRs, help instruct dendritic cells as to when it is appropriate to induce immune tolerance rather than lymphocyte activation.<ref>{{cite journal |vauthors = Maverakis E, Kim K, Shimoda M, Gershwin M, Patel F, Wilken R, Raychaudhuri S, Ruhaak LR, Lebrilla CB | title = Glycans in the immune system and The Altered Glycan Theory of Autoimmunity | journal = J Autoimmun | volume = 57 | issue = 6 | pages = 1–13 | year = 2015 | pmid = 25578468 | doi = 10.1016/j.jaut.2014.12.002 | pmc=4340844}}</ref>

Every helper T-cell is specific to one particular antigen. Only professional [[antigen-presenting cells]] (APCs: macrophages, B lymphocytes, and dendritic cells) are able to activate a resting helper T-cell when the matching antigen is presented.  However, in non-lymphoid organs, macrophages and B cells can only activate [[memory T cells]]{{Citation needed|date=December 2008}} whereas dendritic cells can activate both memory and [[naive T cells]], and are the most potent of all the antigen-presenting cells. In the lymph node and secondary lymphoid organs, all three APCs can activate naive T cells. Whereas mature dendritic cells are able to activate antigen-specific naive CD8<sup>+</sup> T cells, the formation of CD8<sup>+</sup> memory T cells requires the interaction of dendritic cells with CD4<sup>+</sup> [[helper T cells]].<ref name="ReferenceA">{{cite journal | pmid= 15475958| year= 2004| last1= Smith| first1= C. M.| title= Cognate CD4(+) T cell licensing of dendritic cells in CD8(+) T cell immunity| journal= Nature Immunology| volume= 5| issue= 11| pages= 1143–8| last2= Wilson| first2= N. S.| last3= Waithman| first3= J| last4= Villadangos| first4= J. A.| last5= Carbone| first5= F. R.| last6= Heath| first6= W. R.| last7= Belz| first7= G. T.| doi= 10.1038/ni1129| s2cid= 27757632}}</ref> This help from CD4<sup>+</sup> T cells additionally activates the matured dendritic cells and licenses (empowers) them to efficiently induce CD8<sup>+</sup> memory T cells, which are also able to be expanded a second time.<ref name="ReferenceA"/><ref name="ReferenceB">{{cite journal | doi = 10.1002/eji.201444477| pmid = 25211552| title = Concurrent interaction of DCs with CD4+and CD8+T cells improves secondary CTL expansion: It takes three to tango| journal = European Journal of Immunology| volume = 44| issue = 12| pages = 3543–59| year = 2014| last1 = Hoyer| first1 = Stefanie| last2 = Prommersberger| first2 = Sabrina| last3 = Pfeiffer| first3 = Isabell A.| last4 = Schuler-Thurner| first4 = Beatrice| last5 = Schuler| first5 = Gerold| last6 = Dörrie| first6 = Jan| last7 = Schaft| first7 = Niels| s2cid = 5655814| doi-access = free}}</ref> For this activation of CD8+, concurrent interaction of all three cell types, namely CD4<sup>+</sup> T helper cells, CD8<sup>+</sup> T cells and dendritic cells, seems to be required.<ref name="ReferenceB"/>

As mentioned above, mDC probably arise from [[monocyte]]s, white blood cells which circulate in the body and, depending on the right signal, can turn into either dendritic cells or [[macrophage]]s. The monocytes in turn are formed from stem cells in the [[bone marrow]].
Monocyte-derived dendritic cells can be generated in vitro from [[peripheral blood mononuclear cell]] (PBMCs). Plating of PBMCs in a tissue culture flask permits adherence of monocytes. Treatment of these monocytes with interleukin 4 (IL-4) and granulocyte-macrophage colony stimulating factor (GM-CSF) leads to differentiation to immature dendritic cells (iDCs) in about a week. Subsequent treatment with tumor necrosis factor (TNF) further differentiates the iDCs into mature dendritic cells. Monocytes can be induced to differentiate into dendritic cells by a self-peptide Ep1.B derived from [[apolipoprotein E]].<ref>{{cite journal | vauthors = Stephens TA, Nikoopour E, Rider BJ, Leon-Ponte M, Chau TA, Mikolajczak S, Chaturvedi P, Lee-Chan E, Flavell RA, Haeryfar SM, Madrenas J, Singh B | pmid = 18981105 | volume=181 | issue=10 | title=Dendritic cell differentiation induced by a self-peptide derived from apolipoprotein E. | date=Nov 2008 | journal=J Immunol | pages=6859–71 | doi=10.4049/jimmunol.181.10.6859| s2cid = 23966566 | url=http://www.jimmunol.org/content/jimmunol/181/10/6859.full.pdf | doi-access=free }}</ref> These are primarily [[Tolerogenic dendritic cell|tolerogenic plasmacytoid dendritic cells]].<ref>{{cite journal | vauthors = Bellemore SM, Nikoopour E, Au BC, Krougly O, Lee-Chan E, Haeryfar SM, Singh B | year = 2014 | title = Anti-atherogenic peptide Ep1.B derived from Apolipoprotein E induces tolerogenic plasmacytoid dendritic cells | journal = Clin Exp Immunol | volume = 177 | issue = 3| pages = 732–42 | doi = 10.1111/cei.12370 | pmid = 24784480 | pmc = 4137858 }}</ref>

===Life span===
In mice, it has been estimated that dendritic cells are replenished from the blood at a rate of 4000 cells per hour, and undergo a limited number of divisions during their residence in the spleen over 10 to 14 days.<ref>{{Cite journal|last1=Liu|first1=Kang|last2=Waskow|first2=Claudia|last3=Liu|first3=Xiangtao|last4=Yao|first4=Kaihui|last5=Hoh|first5=Josephine|last6=Nussenzweig|first6=Michel|date=June 2007|title=Origin of dendritic cells in peripheral lymphoid organs of mice|journal=Nature Immunology|volume=8|issue=6|pages=578–583|doi=10.1038/ni1462|issn=1529-2908|pmid=17450143|s2cid=24736611}}</ref>

===Research challenges===
The exact genesis and development of the different types and subsets of dendritic cells and their interrelationship is only marginally understood at the moment{{when|date=March 2023}}, as dendritic cells are so rare and difficult to isolate that only in recent years they have become subject of focused research. Distinct surface antigens that characterize dendritic cells have only become known from 2000 on; before that, researchers had to work with a 'cocktail' of several antigens which, used in combination, result in isolation of cells with characteristics unique to DCs.{{citation needed|date=May 2020}}

== Cytokines ==
The dendritic cells are constantly in communication with other cells in the body. This communication can take the form of direct cell–cell contact based on the interaction of cell-surface proteins. An example of this includes the interaction of the membrane proteins of the [[B7 (protein)|B7]] family of the dendritic cell with [[CD28]] present on the [[lymphocyte]]. However, the [[cell–cell interaction]] can also take place at a distance via [[cytokine]]s.{{citation needed|date=May 2020}}

For example, stimulating dendritic cells ''in vivo'' with microbial extracts causes the dendritic cells to rapidly begin producing [[Interleukin 12|IL-12]].<ref name=Reis>{{cite journal  |vauthors=Reis e Sousa C, Hieny S, Scharton-Kersten T, Jankovic D, etal |title=In Vivo Microbial Stimulation Induces Rapid CD40 Ligand–independent Production of Interleukin 12 by Dendritic Cells and their Redistribution to T Cell Areas |journal=J. Exp. Med. |volume=186 |issue=11 |pages=1819–29 |year=1997 |pmid=9382881 |doi=10.1084/jem.186.11.1819 |pmc=2199158}}</ref> IL-12 is a signal that helps send naive [[CD4]] T cells towards a [[T helper cell|Th1]] phenotype. The ultimate consequence is priming and activation of the immune system for attack against the antigens which the dendritic cell presents on its surface. However, there are differences in the cytokines produced depending on the type of dendritic cell. The plasmacytoid DC has the ability to produce huge amounts of [[Interferon type 1|type-1 IFN]]s, which recruit more activated macrophages to allow phagocytosis.<ref name=Siegal>{{cite journal  |vauthors=Siegal FP, Kadowaki N, Shodell M, Fitzgerald-Bocarsly PA, etal | title=The nature of the principal type 1 interferon-producing cells in human blood | journal=Science | date=1999-06-11 | volume=284 | issue=5421 | pages=1835–7 | doi= 10.1126/science.284.5421.1835 | pmid=10364556}}</ref>

== Disease ==

=== Blastic plasmacytoid dendritic cell neoplasm ===
Blastic plasmacytoid dendritic cell neoplasm is a rare type of [[myeloid]] cancer in which malignant pDCs infiltrate the skin, bone marrow, central nervous system, and other tissues. Typically, the disease presents with skin lesions (e.g. nodules, tumors, [[papule]]s, bruise-like patches, and/or ulcers) that most often occur on the head, face, and upper torso.<ref name="pmid29760611">{{cite journal | vauthors = Owczarczyk-Saczonek A, Sokołowska-Wojdyło M, Olszewska B, Malek M, Znajewska-Pander A, Kowalczyk A, Biernat W, Poniatowska-Broniek G, Knopińska-Posłuszny W, Kozielec Z, Nowicki R, Placek W | title = Clinicopathologic retrospective analysis of blastic plasmacytoid dendritic cell neoplasms | journal = Postepy Dermatologii I Alergologii | volume = 35 | issue = 2 | pages = 128–138 | date = April 2018 | pmid = 29760611 | pmc = 5949541 | doi = 10.5114/ada.2017.72269 }}</ref> This presentation may be accompanied by cPC infiltrations into other tissues to result in swollen [[lymph node]]s, enlarged liver, enlarged spleen, symptoms of [[central nervous system]] dysfunction, and similar abnormalities in breasts, eyes, kidneys, lungs, gastrointestinal tract, bone, sinuses, ears, and/or testes.<ref name="pmid28906324"/> The disease may also present as a pDC [[leukemia]], i.e. increased levels of malignant pDC in blood (i.e. >2% of nucleated cells) and bone marrow and evidence (i.e. [[cytopenia]]s) of [[bone marrow failure]].<ref name="pmid28906324">{{cite journal | vauthors = Kim MJ, Nasr A, Kabir B, de Nanassy J, Tang K, Menzies-Toman D, Johnston D, El Demellawy D | title = Pediatric Blastic Plasmacytoid Dendritic Cell Neoplasm: A Systematic Literature Review | journal = Journal of Pediatric Hematology/Oncology | volume = 39 | issue = 7 | pages = 528–537 | date = October 2017 | pmid = 28906324 | doi = 10.1097/MPH.0000000000000964 | s2cid = 11799428 }}</ref> Blastic plasmacytoid dendritic cell neoplasm has a high rate of recurrence following initial treatments with various [[chemotherapy]] regimens. In consequence, the disease has a poor overall prognosis and newer [[Blastic plasmacytoid dendritic cell neoplasm#Treatment|chemotherapeutic]] and novel [[Blastic plasmacytoid dendritic cell neoplasm#Novel treatments|non-chemotherapeutic drug]] regimens to improve the situation are under study.<ref name="pmid29455234">{{cite journal | vauthors = Wang S, Wang X, Liu M, Bai O | title = Blastic plasmacytoid dendritic cell neoplasm: update on therapy especially novel agents | journal = Annals of Hematology | volume = 97 | issue = 4 | pages = 563–572 | date = April 2018 | pmid = 29455234 | doi = 10.1007/s00277-018-3259-z | s2cid = 3627886 }}</ref>

=== Viral infection ===
[[HIV]], which causes [[AIDS]], can bind to dendritic cells via various receptors expressed on the cell. The best studied example is [[DC-SIGN]] (usually on MDC subset 1, but also on other subsets under certain conditions; since not all dendritic cell subsets express DC-SIGN, its exact role in sexual HIV-1 transmission is not clear){{Citation needed|date=February 2011}}. When the dendritic cell takes up HIV and then travels to the lymph node, the virus can be transferred to helper CD4+ T-cells,<ref>{{cite journal |vauthors=Cavrois M, Neidleman J, Kreisberg JF, Greene WC |title=In Vitro Derived Dendritic Cells trans-Infect CD4 T Cells Primarily with Surface-Bound HIV-1 Virions  |journal=PLOS Pathogens |volume=3 |issue=1 |pages=e4 |year=2007 |doi=10.1371/journal.ppat.0030004 |pmid=17238285 |pmc=1779297 |doi-access=free }}</ref> contributing to the developing infection. This infection of dendritic cells by HIV explains one mechanism by which the virus could persist after prolonged [[Antiretroviral drug|HAART]].{{Citation needed|date=February 2011}}

Many other viruses, such as the [[SARS]] virus, seem to use DC-SIGN to 'hitchhike' to its target cells.<ref>{{cite journal |author=Yang, Zhi-Yong|title=pH-Dependent Entry of Severe Acute Respiratory Syndrome Coronavirus Is Mediated by the Spike Glycoprotein and Enhanced by Dendritic Cell Transfer through DC-SIGN |journal=[[Journal of Virology|J. Virol.]] |volume=78 |issue=11 |pages=5642–50 |year=2004 |pmid=15140961 |doi=10.1128/JVI.78.11.5642-5650.2004 |pmc=415834|display-authors=etal}}</ref> However, most work with virus binding to DC-SIGN expressing cells has been conducted using in vitro derived cells such as moDCs.  The physiological role of DC-SIGN in vivo is more difficult to ascertain.

=== Cancer ===
Dendritic cells are usually not abundant at tumor sites, but increased densities of populations of dendritic cells have been associated with better clinical outcome, suggesting that these cells can participate in controlling cancer progression.<ref name="pmid25446897">{{cite journal | vauthors = Broz ML, Binnewies M, Boldajipour B, Nelson AE, Pollack JL, Erle DJ, Barczak A, Rosenblum MD, Daud A, Barber DL, Amigorena S, Van't Veer LJ, Sperling AI, Wolf DM, Krummel MF | title = Dissecting the tumor myeloid compartment reveals rare activating antigen-presenting cells critical for T cell immunity | journal = Cancer Cell | volume = 10 | issue = 26 | pages = 638–52 | date = November 2014 | pmid = 25446897 | doi = 10.1016/j.ccell.2014.09.007 | pmc=4254577 }}</ref><ref name="pmid30955881">{{cite journal | vauthors = Binnewies M, Mujal AM, Pollack JL, Combes AJ, Hardison EA, Barry KC, Tsui J, Ruhland MK, Kersten K, Abushawish MA, Spasic M, Giurintano JP, Chan V, Daud AI, Ha P, Ye CJ, Roberts EW, Krummel MF | title = Unleashing Type-2 Dendritic Cells to Drive Protective Antitumor CD4+ T Cell Immunity | journal = Cell | volume = 177 | issue = 3 | pages = 556–571 | date = April 2019 | pmid = 30955881 | doi = 10.1016/j.cell.2019.02.005 | pmc = 6954108 }}</ref> Lung cancers have been found to include four different subsets of dendritic cells: three classical dendritic cell subsets and one plasmacytoid dendritic cell subset.<ref name="pmid30979687">{{cite journal | vauthors = Zilionis R, Engblom C, Pfirschke C, Savova V, Zemmour D, Saatcioglu HD, Krishnan I, Maroni G, Meyerovitz CV, Kerwin CM, Choi S, Richards WG, De Rienzo A, Tenen DG, Bueno R, Levantini E, Pittet MJ, Klein AM | title = Single-Cell Transcriptomics of Human and Mouse Lung Cancers Reveals Conserved Myeloid Populations across Individuals and Species | journal = Immunity | volume = 50 | issue = 5 | pages = 1317–1334 | date = April 2019 | pmid = 30979687 | doi = 10.1016/j.immuni.2019.03.009 | pmc = 6620049 }}</ref> At least some of these dendritic cell subsets can activate CD4+ helper T cells and [[Cytotoxic T cell|CD8+ cytotoxic T cells]], which are immune cells that can also suppress [[tumor]] growth. However, dendritic cell activity is commonly suppressed by regulatory T cells and multiple other factors.<ref>{{cite journal | url=https://doi.org/10.1038/s41586-020-2134-y | doi=10.1038/s41586-020-2134-y | title=A conserved dendritic-cell regulatory program limits antitumour immunity | date=2020 | last1=Maier | first1=Barbara | last2=Leader | first2=Andrew M. | last3=Chen | first3=Steven T. | last4=Tung | first4=Navpreet | last5=Chang | first5=Christie | last6=Leberichel | first6=Jessica | last7=Chudnovskiy | first7=Aleksey | last8=Maskey | first8=Shrisha | last9=Walker | first9=Laura | last10=Finnigan | first10=John P. | last11=Kirkling | first11=Margaret E. | last12=Reizis | first12=Boris | last13=Ghosh | first13=Sourav | last14=d'Amore | first14=Natalie Roy | last15=Bhardwaj | first15=Nina | last16=Rothlin | first16=Carla V. | last17=Wolf | first17=Andrea | last18=Flores | first18=Raja | last19=Marron | first19=Thomas | last20=Rahman | first20=Adeeb H. | last21=Kenigsberg | first21=Ephraim | last22=Brown | first22=Brian D. | last23=Merad | first23=Miriam | journal=Nature | volume=580 | issue=7802 | pages=257–262 | pmid=32269339 | pmc=7787191 | bibcode=2020Natur.580..257M }}</ref> Dendritic cell stimulating treatments, such as dendritic cell based vaccinations, have been emerging as a treatment with varying success.<ref>{{Cite journal |last=Saxena |first=Mansi |last2=Bhardwaj |first2=Nina |date=February 2018 |title=Re-Emergence of Dendritic Cell Vaccines for Cancer Treatment |url=https://linkinghub.elsevier.com/retrieve/pii/S2405803317302406 |journal=Trends in Cancer |language=en |volume=4 |issue=2 |pages=119–137 |doi=10.1016/j.trecan.2017.12.007 |pmc=5823288 |pmid=29458962}}</ref> In experimental models, dendritic cells have also been shown to contribute to the success of cancer immunotherapies, for example with the immune checkpoint blocker anti-PD-1.<ref name="pmid27775706">{{cite journal | vauthors = Moynihan KD, Opel CF, Szeto GL, Tzeng A, Zhu EF, Engreitz JM, Williams RT, Rakhra K, Zhang MH, Rothschilds AM, Kumari S, Kelly RL, Kwan BH, Abraham W, Hu K, Mehta NK, Kauke MJ, Suh H, Cochran JR, Lauffenburger DA, Wittrup KD, Irvine DJ | title = Eradication of large established tumors in mice by combination immunotherapy that engages innate and adaptive immune responses | journal = Nat Med | volume = 22 | issue =  12| pages = 1402–1410 | date = December 2016 | pmid = 27775706 | doi = 10.1038/nm.4200 | pmc= 5209798}}</ref><ref name="pmid30552023">{{cite journal | vauthors = Garris CS, Arlauckas SP, Kohler RH, Trefny MP, Garren S, Piot C, Engblom C, Pfirschke C, Siwicki M, Gungabeesoon J, Freeman GJ, Warren SE, Ong S, Browning E, Twitty CG, Pierce RH, Le MH, Algazi AP, Daud AI, Pai SI, Zippelius A, Weissleder R, Pittet MJ | title = Successful Anti-PD-1 Cancer Immunotherapy Requires T Cell-Dendritic Cell Crosstalk Involving the Cytokines IFN-γ and IL-12 | journal = Immunity | volume = 49 | issue = 6 | pages = 1148–1161 | date = December 2018 | pmid = 30552023 | doi = 10.1016/j.immuni.2018.09.024 | pmc= 6301092 }}</ref>

=== Autoimmunity ===
Altered function of dendritic cells is also known to play a major or even key role in [[allergy]] and [[autoimmune disease]]s like [[lupus erythematosus]] and inflammatory bowel diseases ([[Crohn's disease]] and [[ulcerative colitis]]).<ref name=Baumgart>{{cite journal | vauthors = Baumgart DC, Metzke D, Schmitz J, Scheffold A, Sturm A, Wiedenmann B, Dignass AU | year = 2005 | title = Patients with active inflammatory bowel disease lack immature peripheral blood plasmacytoid and myeloid dendritic cells | journal = Gut | volume = 54 | issue = 2 | pages = 228–36 | pmid = 15647187 | doi = 10.1136/gut.2004.040360 | pmc = 1774844}}</ref><ref name=Baumgart2>{{cite journal | vauthors = Baumgart DC, Thomas S, Przesdzing I, Metzke D, Bielecki C, Lehmann SM, Lehnardt S, Dorffel Y, Sturm A, Scheffold A, Schmitz J, Radbruch A | year = 2009 | title = Exaggerated inflammatory response of primary human myeloid dendritic cells to lipopolysaccharide in patients with inflammatory bowel disease | journal = Clin Exp Immunol | volume = 157 | issue = 3 | pages = 423–36 | pmid = 19664152 | doi = 10.1111/j.1365-2249.2009.03981.x | pmc = 2745038}}</ref><ref name=Baumgart3>{{cite journal | vauthors = Baumgart DC, Carding SR | year = 2007 | title = Inflammatory bowel disease: cause and immunobiology | journal = The Lancet | volume = 369 | issue = 9573 | pages = 1627–40 | pmid =  17499605 | doi = 10.1016/S0140-6736(07)60750-8| s2cid = 13544348 }}</ref>

==Other animals==
The above applies to humans. In other organisms, the function of dendritic cells can differ slightly. However, the principal function of dendritic cells as known to date is always to act as an immune sentinel. They survey the body and collect information relevant to the immune system, they are then able to instruct and direct the adaptive arms to respond to challenges.

In addition, an immediate precursor to myeloid and lymphoid dendritic cells of the spleen has been identified.<ref name=Naik>{{cite journal  |vauthors=Naik SH, Metcalf D, van Nieuwenhuijze A, etal | journal=Nature Immunology | title=Intrasplenic steady-state dendritic cell precursors that are distinct from monocytes |date=June 2006 | volume=7 | issue=6 | pages=663–71 | doi=10.1038/ni1340 | pmid=16680143| s2cid=539437 }}</ref> This precursor, termed pre-DC, lacks MHC class II surface expression, and is distinct from monocytes, which primarily give rise to DCs in non-lymphoid tissues.

Dendritic cells have also been found in turtles.<ref>{{cite journal | last=Pérez-Torres | first=A |author2=Millán-Aldaco DA |author3=Rondán-Zárate A  | title=Epidermal Langerhans cells in the terrestrial turtle, ''Kinosternum integrum'' | journal=Developmental and Comparative Immunology | volume=19 | issue=3 | pages=225–236 |date=May–June 1995 | pmid=8595821 | doi=10.1016/0145-305X(95)00006-F }}</ref>

Dendritic cells have been found in rainbow trout (''Oncorhynchus mykiss'') and zebrafish (''Danio rerio'') but their role is still not fully understood <ref>Salinas, I., & Parra, D. (2015). Fish mucosal immunity: Intestine. In Mucosal Health in Aquaculture. Elsevier Inc. https://doi.org/10.1016/B978-0-12-417186-2.00006-6</ref>

==Media==
<gallery>
Image:Dendritic cell.JPG|A dendritic cell
Image:S8-Dendritic Cells Dragging Conidia in Collagen.ogg|A well-resolved dendritic cell drags a [[conidium]] through a distance of up to 9 μm. The conidium, however, is not [[phagocytosis|phagocytosed]] by the cell. The observation was made over 3 h with one frame every 30 s.
Image:S6-Dendritic Cells with Conidia in Collagen.ogv|A single dendritic cell can be seen here efficiently taking up at least four conidia in its vicinity.
</gallery>

==See also==
*[[Histiocyte]]
*[[Macrophage]]
*[[List of human clusters of differentiation]] for a list of CD molecules (such as [[CD80]] and [[CD86]])
*[[List of distinct cell types in the adult human body]]

== References ==
{{Reflist|30em}}

== External links ==
{{Sister project links |wikt=yes |commons=Category:Dendritic cell |b=no |n=no |q=no |s=no |v=no |species=no }}
*[https://web.archive.org/web/20151225110926/http://u1019.lille.inserm.fr/research-activities/?lang=en] Website of the Center for Infection and Immunity of Lille contains information on DCs and their study in research, link currently dead
* {{MeSH name|Dendritic+Cells}}
* [https://web.archive.org/web/20070220084548/http://www.dc2007.eu/ www.dc2007.eu 5th International Meeting on Dendritic Cell Vaccination and other Strategies to tip the Balance of the Immune System]
*[http://www.rockefeller.edu/labheads/steinman/steinman-lab.php Website of Ralph M. Steinman at The Rockefeller University] {{Webarchive|url=https://web.archive.org/web/20090627151040/http://www.rockefeller.edu/labheads/steinman/steinman-lab.php |date=27 June 2009 }} contains information on DCs, links to articles, pictures and videos
*[http://news.bbc.co.uk/2/hi/health/7888042.stm "Cancer 'danger receptor' found"], [[BBC News]], 15 February 2009

{{Myeloid blood cells and plasma }}
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[[Category:Antigen presenting cells]]
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[[Category:Human cells]]
[[Category:Immunology]]
[[Category:Mononuclear phagocytes]]