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Paneth cells provide host defense against microbes in the small intestine. They are functionally similar to neutrophils. When exposed to bacteria or bacterial antigens, Paneth cells secrete a number of antimicrobial molecules into the lumen of the crypt, thereby contributing to maintenance of the gastrointestinal barrier.

Small intestinal crypts house stem cells that serve to constantly replenish epithelial cells that die and are lost from the villi. Protection of these stem cells is essential for long-term maintainance 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 cryptdins. These peptides have hydrophobic and positively-charged domains that can interact with phospholipids in 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 killing. Due to the higher concentration of negatively-charged phospholipids in bacterial membranes than vertebrate membranes, defensins preferentially bind to and disrupt bacterial cells, sparing the cells they are functioning to protect.

Paneth cells are stimulated to secrete defensins when exposed to bacteria (both Gram positive and negative types) or such bacterial products as lipopolysaccharide, muramyl dipeptide and lipid A.

In addition to defensins, Paneth cells secrete lysozyme and phospholipase A2, both of which have clear antimicrobial activity. This battery of secretory molecules gives Paneth cells a potent arsenal against a broad spectrum of agents, including bacteria, fungi and even some enveloped viruses.

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Paneth cells
Paneth cells provide host defense against microbes in the small intestine. They are functionally similar to neutrophils. When exposed to bacteria or 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.

Stem cells

Small intestinal crypts house stem cells that serve to constantly replenish epithelial cells that die and are lost from the villi.

Protection of these stem cells is 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.

Secretions

Defensins

The principal defense molecules secreted by Paneth cells are alpha-defensins, also known as cryptdin.[1] These peptides have hydrophobic and positively-charged domains that can interact with phospholipids in 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.[2]

Paneth cells are stimulated to secrete defensins when exposed to bacteria (both Gram positive and negative types) or such bacterial products as lipopolysaccharide, muramyl dipeptide and lipid A.

Other secretions

In addition to defensins, Paneth cells secrete lysozyme and phospholipase A2, both of which have clear antimicrobial activity. This battery of secretory molecules gives Paneth cells a potent arsenal against a broad spectrum of agents, including bacteria, fungi and even some enveloped viruses.

References

1. ^ Wilson C, Ouellette A, Satchell D, Ayabe T, López-Boado Y, Stratman J, Hultgren S, Matrisian L, Parks W (1999). "Regulation of intestinal alpha-defensin activation by the metalloproteinase matrilysin in innate host defense.". Science 286 (5437): 113-7. PMID 10506557. 
2. ^ Ayabe T, Satchell D, Wilson C, Parks W, Selsted M, Ouellette A (2000). "Secretion of microbicidal alpha-defensins by intestinal Paneth cells in response to bacteria.". Nat Immunol 1 (2): 113-8. PMID 11248802. 

Further reading

  • Ganz T (1999). "Defensins and host defense.". Science 286 (5439): 420-1. PMID 10577203. 
  • Ganz T (2000). "Paneth cells--guardians of the gut cell hatchery.". Nat Immunol 1 (2): 99-100. PMID 11248797. 

External links

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Digestive system, physiology: gastrointestinal physiology
Enteric nervous systemMeissner's plexus - Auerbach's plexus
ExocrineChief cells (Pepsinogen) - Parietal cells (Gastric acid, Intrinsic factor) - Goblet cells (Mucus)
Endocrine/paracrineG cells (gastrin), D cells (somatostatin) - ECL cells (Histamine) - enterogastrone: I cells (CCK), K cells (GIP), S cells (secretin)
BorderBrunner's glands - Paneth cells - Enterocytes
FluidsSaliva - Bile - Intestinal juice - Gastric juice - Pancreatic juice
ProcessesSwallowing - Vomiting - Peristalsis (Interstitial cell of Cajal) - Migrating motor complex - Borborygmus - Gastrocolic reflex - Segmentation contractions - Defecation
microorganism (also spelled as microrganism) or microbe is an organism that is microscopic (too small to be seen by the human eye). The study of microorganisms is called microbiology.
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In biology the small intestine is the part of the gastrointestinal tract (gut) between the stomach and the large intestine and includes the duodenum, jejunum, and ileum. It is where the vast majority of digestion takes place.
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Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of white blood cells and form an integral part of the immune system. Their name arrives from staining characteristics on hematoxylin and eosin (H&E) histological preparations.
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Bacteria

Phyla

Actinobacteria
Aquificae
Chlamydiae
Bacteroidetes/Chlorobi
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Deinococcus-Thermus
Dictyoglomi
Fibrobacteres/Acidobacteria
Firmicutes
Fusobacteria
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An antigen or immunogen is a molecule that stimulates an immune response. The word originated from the notion that they can stimulate antibody generation. We now know that the immune system does not only consist of antibodies.
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An antimicrobial is a substance that kills or inhibits the growth of microbes such as bacteria (antibacterial activity), fungi (antifungal activity), viruses (antiviral activity), or parasites (anti-parasitic activity).
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molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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Lumen can mean:
  • Lumen (unit), the SI unit of luminous flux
  • Lumen (anatomy), the cavity or channel within a tubular structure
  • Thylakoid lumen, the inner membrane space of the chloroplast

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Crypts are anatomical structures that are narrow but deep invaginations into a larger structure.

One common type of anatomical crypt is the Crypts of Lieberkühn. However, it is not the only type: some types of tonsils also have crypts.
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Joseph Paneth (1857-1890) was an Austrian physiologist from Vienna. He was a professor at the Universities of Breslau and Vienna. He was the father of chemist Friedrich Adolf Paneth (1887-1958).
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epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.
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Villus (Latin: "shaggy hair"[1], plural villi) can refer to:
  • Intestinal villus. This is the most common meaning when not more precisely specified
  • Chorionic villi, found on the surface of the outermost membrane (the chorion) of the fetus

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Stem cells are primal cells found in all multi-cellular organisms. They retain the ability to renew themselves through mitotic cell division and can differentiate into a diverse range of specialized cell types.
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epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.
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Defensins are small (15-20 residue) cysteine-rich cationic proteins found in both vertebrates and invertebrates. They are active against bacteria, fungi and enveloped viruses. They consist of 15-20 amino acids including six to eight conserved cysteine residues.
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Peptides (from the Greek πεπτίδια, "small digestibles") are short polymers formed from the linking, in a defined order, of α-amino acids.
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hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water [1].
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U indicates the uncharged hydrophobic portion of the molecule, highlighted in blue.]]

Phospholipids are a class of lipids, and a major component of all biological membranes, along with glycolipids, cholesterol and proteins.
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Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.[1] Gram-positive bacteria appear blue or violet under a microscope, while Gram-negative bacteria appear red or pink.
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Lipopolysaccharide (LPS) is a large molecule consisting of a lipid and a polysaccharide (carbohydrate) joined by a covalent bond.

Functions

LPS is a major component of the outer membrane of Gram-negative bacteria, contributing greatly to the structural integrity of
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Muramyl dipeptide is a peptidoglycan constituent of both Gram positive and Gram negative bacteria.

See also

  • dipeptide

External links

  • PubChem 40846

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Lipid A is a lipid component of an endotoxin held responsible for toxicity of Gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS, also called endotoxin) molecule, and its hydrophobic nature allows it to anchor the LPS to the outer
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Lysozyme is a 14.4 kilodalton enzyme (EC 3.2.1.17 ) that damages bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins.
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Phospholipases A2 (PLA2s) EC 3.1.1.4 are enzymes that specifically hydrolyze the sn-2 fatty acid acyl bond of phospholipids, producing a free fatty acid and a lyso-phospholipid.
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An antimicrobial is a substance that kills or inhibits the growth of microbes such as bacteria (antibacterial activity), fungi (antifungal activity), viruses (antiviral activity), or parasites (anti-parasitic activity).
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Eukarya
Whittaker & Margulis, 1978
(unranked) Opisthokonta

Kingdom: Fungi
(L., 1753) R.T. Moore, 1980[1]

Subkingdom/Phyla

Chytridiomycota
Blastocladiomycota

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