- Paneth cell
Paneth cells provide host defense against
microbesin the small intestine. They are functionally similar to neutrophils. When exposed to bacteriaor bacterial antigens, Paneth cells secrete a number of antimicrobial molecules into the lumen of the crypt, thereby contributing to maintenance of the gastrointestinal barrier. Paneth cells are named after Joseph Paneth(1857–1890), Austrian physician.
Small intestinal crypts house stem cells that serve to constantly replenish
epithelial cellsthat die and are lost from the villi.
Protection of these
stem cellsis essential for long-term maintenance of the intestinal epithelium, and the location of Paneth cells adjacent to stem cells suggests that they play a critical role in defending epithelial cell renewal.
The principal defense molecules secreted by Paneth cells are alpha-defensins, also known as
cryptdin. [ cite journal | author = Wilson C, Ouellette A, Satchell D, Ayabe T, López-Boado Y, Stratman J, Hultgren S, Matrisian L, Parks W | title = Regulation of intestinal alpha-defensin activation by the metalloproteinase matrilysin in innate host defense. | journal = Science | volume = 286 | issue = 5437 | pages = 113–7 | year = 1999 | pmid = 10506557 | doi = 10.1126/science.286.5437.113] These peptideshave hydrophobicand positively-charged domains that can interact with phospholipidsin cell membranes. This structure allows defensins to insert into membranes, where they interact with one another to form pores that disrupt membrane function, leading to cell lysis. Due to the higher concentration of negatively-charged phospholipids in bacterial than vertebrate cell membranes, defensins preferentially bind to and disrupt bacterial cells, sparing the cells they are functioning to protect. [cite journal | author = Ayabe T, Satchell D, Wilson C, Parks W, Selsted M, Ouellette A | title = Secretion of microbicidal alpha-defensins by intestinal Paneth cells in response to bacteria. | journal = Nat Immunol | volume = 1 | issue = 2 | pages = 113–8 | year = 2000 | pmid = 11248802 | doi = 10.1038/77783]
Paneth cells are stimulated to secrete defensins when exposed to bacteria (both Gram positive and negative types) or such bacterial products as
lipopolysaccharide, muramyl dipeptideand lipid A.
In addition to defensins, Paneth cells secrete
lysozymeand phospholipase A2, both of which have clear antimicrobialactivity. This battery of secretory molecules gives Paneth cells a potent arsenal against a broad spectrum of agents, including bacteria, fungiand even some enveloped viruses.
* - "Endocrine System: duodenum, enteroendocrine cells"
* - "Digestive System: Alimentary Canal - duodenum, paneth cells"
* [http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/paneth.html Overview and diagram at colostate.edu]
* [http://meded.ucsd.edu/hist-img-bank/chapter_6/Slide_94_crypts_duodenum/pages/b.18.104.22.168.htm Histology at ucsd.edu]
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