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==Overview==

'''Monoclonal antibodies''' ('''mAb''' or '''moAb''') are [[antibody|antibodies]] that are identical because they are produced by one type of [[immune cell]] that are all [[clone (genetics)|clone]]s of a single parent cell. Given (almost) any substance, it is possible to create monoclonal antibodies that specifically bind to that substance; they can then serve to detect or purify that substance. This has become an important tool in [[biochemistry]], [[molecular biology]] and [[medicine]]. When used as medications, the generic name ends in ''-mab'' (see "[[Nomenclature of monoclonal antibodies]]").

== Discovery ==

The idea of a "magic bullet" was first proposed by Paul Ehrlich who at the beginning of the 20th century postulated that if a compound could be made that selectively targeted a disease-causing organism, then a toxin for that organism could be delivered along with the agent of selectivity.

In the 1970s the B-cell cancer [[myeloma]] was known, and it was understood that these cancerous B-cells all produce a single type of antibody (a [[paraprotein]]). This was used to study the structure of antibodies, but it was not yet possible to produce identical antibodies specific to a given antigen. 

A process of producing monoclonal antibodies involving human-mouse hybrid cells was described by Jerrold Schwaber in 1973<ref>Schwaber, J and Cohen, E. P., "Human x Mouse Somatic Cell Hybrid Clones Secreting Immunoglobulins of Both Parental Types," Nature, 244 (1973), 444--447.</ref> and remains widely cited among those using human-derived hybridomas.<ref>Science Citation Index</ref>, but claims to priority have been controversial. A science history paper on the subject gave some credit to Schwaber for inventing a technique that was widely cited, but stopped short of suggesting that he had been cheated<ref>Alberto Cambrosio Peter Keating, Journal of the History of Biology. Between fact and technique: The beginnings of hybridoma technology, Volume 25,Issue 2,175- 230.[http://www.springerlink.com/content/t265n3355pm24326] </ref>. The invention is generally accredited to Georges Köhler, [[César Milstein]], and [[Niels Kaj Jerne]] in 1975;<ref>Kohler G, Milstein C. ''Continuous cultures of fused cells secreting antibody of predefined specificity.'' [[Nature (journal)|Nature]] 1975;256:495-7. PMID 1172191. Reproduced in J Immunol 2005;174:2453-5. PMID 15728446.</ref> who shared the [[Nobel Prize in Physiology or Medicine]] in 1984 for the discovery.
The key idea was to use a line of myeloma cells that had lost their ability to secrete antibodies, come up with a technique to fuse these cells with healthy antibody producing B-cells, and be able to select for the successfully fused cells.

In 1988 Greg Winter and his team pioneered the techniques to humanize monoclonal antibodies,<ref>Riechmann L, Clark M, Waldmann H, Winter G. ''Reshaping human antibodies for therapy.'' [[Nature (journal)|Nature]] 1988;332:323-7. PMID 3127726.</ref> removing the reactions that many monoclonal antibodies caused in some patients.

== Production ==
[[Image:monoclonal_antibodies3.jpg|200px|thumb|right|Researchers looking at slides of cultures of cells that make monoclonal antibodies. These are grown in a lab and the researchers are analyzing the products to select the most promising of them.]]
[[Image:monoclonal_antibodies4.jpg|200px|thumb|right|Monoclonal antibodies can be grown in unlimited quantities in the bottles shown in this picture.]]
[[Image:monoclonal_antibodies1.jpg|200px|thumb|right|Technician's hand filling wells with a liquid for a research test. This test involves preparation of cultures in which hybrids are grown in large quantities to produce desired antibody. This is effected by fusing [[Multiple myeloma|myeloma]] cell and [[mus musculus|mouse]] [[lymphocyte]] to form a hybrid cell ([[hybridoma]]).]]
[[Image:monoclonal_antibodies2.jpg|200px|thumb|right|Lab technician bathing prepared slides in a solution. This technician is involved in the preparation of slides of monoclonal antibodies for researchers. These highly specific cells shown are those labeling human [[breast cancer]].]]

===Hybridoma Cell Production===
Monoclonal antibodies are made by fusing the spleen cells from a mouse that has been immunized with the desired antigen with myeloma cells.
Polyethylene glycol is used to fuse of adjacent plasma membranes, but the success rate is low so a selective medium is used in which only fused cells can grow. This is because myeloma cells that have lost the ability to synthesize hypoxanthine-guanine-phosphoribosyl transferase (HGPRT). [[Image:monoclonal.jpg|200px|thumb|left|]]
This enzyme enables cells to synthesize purines using an extracellular source of hypoxanthine as a precursor ordinarily, the absence of HGPRT is not a problem for the cell because cells have an alternate biochemical pathway that they can use to synthesize purines. However, when cells are exposed to aminopterin (a folic acid analogue), they are unable to use this other, rescue, pathway and are now fully dependent on HGPRT for survival. 
The selective culture medium is called HAT medium because it contains:<br /> 
•	Hypoxanthine <br />
•	Aminopterin <br />
•	Thymidine<br />
This medium is selective for fused, (hydridoma) cells because unfused myeloma cells cannot grow because they lack HGPRT.  Unfused normal spleen cells cannot grow indefinitely because of their limited life span. However, hybridoma cells are able to grow indefinitely because the spleen cell partner supplies HGPRT and the myeloma partner is immortal because it is a cancer cell.
The fused hybrid cells are called [[hybridomas]], and since they are derived from cancer cells, are immortal and can be grown idefinitely. 

This mixture of cells is then diluted and clones are grown from single parent cells. The antibodies secreted by the different clones are then tested for their ability to bind to the antigen (for example with a test such as EIA or Antigen Microarray Assay) or immuno-[[dot blot]], and the most productive and stable clone is then grown in culture medium to a high volume. When the hybridoma cells are injected in [[mus musculus|mice]] (in the [[peritoneum|peritoneal cavity]], the gut), they produce tumors containing an antibody-rich fluid called [[ascites]] fluid.

The medium must be enriched during selection to further favour hybridoma growth. This can be achieved by the use of a layer of feeder fibrocyte cells or supplement medium such as [[briclone]]. Production in cell culture is usually preferred as the ascites technique is painful to the animal and if replacement techniques exist, is considered unethical.

===Recombinant===
The production of [[Recombinant DNA|Recombinant]] monoclonal antibodies involves technologies, referred to as ''repertoire [[cloning]]'' or ''[[phage display]]/[[yeast display]]''. Recombinant antibody engineering involves the use of [[viruses]] or [[yeast]] to create antibodies, rather than mice. These techniques rely on rapid cloning of immunoglobulin gene segments to create libraries of antibodies with slightly different [[amino acid]] sequences from which antibodies with desired specificities can be selected.<ref>{{cite journal |author=Siegel DL |title=Recombinant monoclonal antibody technology |journal=Transfusion clinique et biologique : journal de la Société française de transfusion sanguine |volume=9 |issue=1 |pages=15-22 |year=2002 |pmid=11889896 |doi=}}</ref> These techniques can be used to enhance: the specificity with which antibodies recognize antigens, their stability in various environmental conditions, their therapeutic efficacy, and their detectability in diagnostic applications.<ref>{{cite journal |author=Schmitz U, Versmold A, Kaufmann P, Frank HG |title=Phage display: a molecular tool for the generation of antibodies--a review |journal=Placenta |volume=21 Suppl A |issue= |pages=S106-12 |year=2000 |pmid=10831134 |doi=}}</ref> Fermentation chambers have been used to produce these antibodies on a large scale.

== Applications ==

Once monoclonal antibodies for a given substance have been produced, they can be used to detect the presence and quantity of this substance, for instance in a [[Western blot]] test (to detect a protein on a membrane) or an [[immunofluorescence]] test (to detect a substance in a cell). They are also very useful in immunohistochemistry which detect antigen in fixed tissue sections. Monoclonal antibodies can also be used to purify a substance with techniques called [[immunoprecipitation]] and [[affinity chromatography]].

=== Monoclonal antibodies for cancer treatment ===
{{main|Monoclonal antibody therapy}}
One possible treatment for [[cancer]] involves monoclonal antibodies that bind only to cancer cell-specific [[antigens]] and induce an immunological response against the target cancer cell. Such mAb could also be modified for delivery of a [[toxin]], [[radioisotope]], [[cytokine]] or other active conjugate; it is also possible to design [[bispecific antibodies]] that can bind with their Fab regions both to target antigen and to a conjugate or effector cell. In fact, every intact antibody can bind to cell receptors or other proteins with its Fc region. The illustration below shows all these possibilities:

[[Image:MonoclonalAb.jpg|frame|none|'''Monoclonal antibodies for cancer.''' [[ADEPT]], antibody directed enzyme prodrug therapy; ADCC, antibody dependent cell-mediated cytotoxicity; CDC, complement dependent cytotoxicity; MAb, monoclonal antibody; scFv, single-chain Fv fragment.<ref>Modified from Carter P: Improving the efficacy of antibody-based cancer therapies. Nat Rev Cancer 2001;1:118-129</ref>]]

=== Chimeric and humanized antibodies ===
{{main|humanized antibodies}}
One problem in medical applications is that the standard procedure of producing monoclonal antibodies yields mouse antibodies. Although murine antibodies are very similar to human ones there are differences. The human [[immune system]] hence recognizes mouse antibodies as foreign, rapidly removing them from circulation and causing systemic inflammatory effects.

A solution to this problem would be to generate human antibodies directly from humans. However, this is not easy, primarily because it is generally not seen as ethical to challenge humans with antigen in order to produce antibody; while the ethics of doing the same to non-humans is a matter of debate. Furthermore, it is not easy to generate human antibodies against human tissues.

Various approaches using recombinant DNA technology to overcome this problem have been tried since the late 1980s. In one approach, one takes the DNA that encodes the binding portion of monoclonal mouse antibodies and merges it with human antibody producing DNA. One then uses [[mammal]]ian [[cell culture]]s to express this DNA and produce these half-mouse and half-human antibodies. (Bacteria cannot be used for this purpose, since they cannot produce this kind of [[glycoprotein]].) Depending on how big a part of the mouse antibody is used, one talks about '''chimeric antibodies''' or '''humanized antibodies'''. 
Another approach involves mice [[Genetically modified organism|genetically engineered]] to produce more human-like antibodies. Monoclonal antibodies have been generated and approved to treat: [[cancer]], [[cardiovascular disease]], [[inflammatory diseases]], [[macular degeneration]],
[[transplant rejection]], [[multiple sclerosis]], and [[viral infection]] (see [[monoclonal antibody therapy]]).

In August 2006 the [[Pharmaceutical Research and Manufacturers of America]] reported that U.S. companies had 160 different monoclonal antibodies in clinical trials or awaiting approval by the [[Food and Drug Administration]].<ref>''PhRMA Reports Identifies More than 400 Biotech Drugs in Development.'' Pharmaceutical Technology, August 24, 2006. Retrieved 2006-09-04.</ref>

==See also==
*[[Monoclonal antibody therapy]]
*[[Nomenclature of monoclonal antibodies]]
*[[Polyclonal antibody]]
*[[Nanobodies]]

== References ==
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== External links ==
<!-- ATTENTION! Please do not add links without discussion and consensus on the talk page. Undiscussed links will be removed. -->
*[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Monoclonals.html Monoclonal Antibodies], from John W. Kimball's online biology textbook
* {{MeshName|Monoclonal+antibodies}}

{{immune_system}}
{{Template group
|title = Monoclonal antibodies
|list  = 
{{Humanmonoclonals}}
{{Mousemonoclonals}}
{{Chimericmonoclonals}}
{{Humanizedmonoclonals}}
{{Rat-murinehybridmonoclonals}}
{{chimeric-humanizedmonoclonals}}
}}

[[Category:Immunology]]
[[Category:Biotechnology]]
[[Category:Immune system]]
[[Category:Monoclonal antibodies| ]]

[[de:Monoklonaler Antikörper]]
[[es:Anticuerpo monoclonal]]
[[fr:Anticorps monoclonaux]]
[[it:Anticorpi monoclonali]]
[[he:נוגדנים חד-שבטיים]]
[[ja:モノクローナル抗体]]
[[pl:Przeciwciała monoklonalne]]
[[pt:Anticorpo monoclonal]]
[[ru:Моноклональные антитела]]
[[sl:Monoklonska protitelesa]]
[[sv:Monoklonal antikropp]]
[[zh:单克隆抗体]]

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