Editing Exotoxin (section)

{{Short description|Toxin from bacteria that destroys or disrupts cells}}
{{More citations needed|date=June 2010}}
[[File:Immune Response to Exotoxins.png|thumb|373x373px|
This figure shows that exotoxins are secreted by bacterial cells, ''Clostridium botulinum'' for example, and are toxic to somatic cells. Somatic cells have [[antibody|antibodies]] on the cell wall to target exotoxins and bind to them, preventing the invasion of somatic cells. The binding of the exotoxin and antibody forms an antigen-antibody interaction and the exotoxins are targeted for destruction by the immune system. If this interaction does not happen, the exotoxins bind to the [[exotoxin receptor]]s that are on the cell surface and causes death of the host cell by inhibiting protein synthesis. This figure also shows that the application of heat or chemicals to exotoxins can result in the deactivation of exotoxins. The deactivated exotoxins are called toxoids and they are not harmful to somatic cells.
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An '''exotoxin''' is a [[toxin]] secreted by [[bacteria]].<ref>{{cite book |editor-last1=Ryan |editor-first1=Kenneth J. |editor-last2=Ray |editor-first2=C. George |title=Sherris medical microbiology |year=2010 |publisher=McGraw Hill Medical |location=New York |isbn=978-0-07-160402-4 |edition=5th}}</ref> An exotoxin can cause damage to the host by destroying cells or disrupting normal [[cellular metabolism]]. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to [[endotoxin]]s, may be released during [[lysis]] of the cell. Gram negative pathogens may secrete outer membrane vesicles containing lipopolysaccharide endotoxin and some virulence proteins in the bounding membrane along with some other toxins as intra-vesicular contents, thus adding a previously unforeseen dimension to the well-known eukaryote process of [[membrane vesicle trafficking]], which is quite active at the [[Host–pathogen interaction|host–pathogen interface]].

They may exert their effect locally or produce systemic effects. Well-known exotoxins include: [[botulinum toxin]] produced by ''[[Clostridium botulinum]]''; ''[[Corynebacterium diphtheriae]]'' toxin, produced during life-threatening symptoms of [[diphtheria]]; [[tetanospasmin]] produced by ''[[Clostridium tetani]]''. The toxic properties of most exotoxins can be inactivated by heat or chemical treatment to produce a [[toxoid]]. These retain their antigenic specificity and can be used to produce [[antitoxin]]s and, in the case of diphtheria and tetanus toxoids, are used as vaccines.

Exotoxins are susceptible to [[antibodies]] produced by the [[immune system]], but some exotoxins are so toxic that they may be fatal to the host before the immune system has a chance to mount defenses against them. In such cases, antitoxin, anti-serum containing antibodies, can sometimes be injected to provide [[passive immunity]].