Paneth cells
Encyclopedia
Paneth cells, along with goblet cells, enterocytes, and enteroendocrine cells
, represent the principal cell types of the epithelium
of the small intestine. (A few may also be found sporadically in the cecum and appendix.) They are identified microscopically by their location just below the intestinal stem cells in the intestinal glands and the large eosinophilic
refractile granules that occupy most of their cytoplasm. These granules consist of several anti-microbial compounds and other compounds that are known to be important in immunity and host-defense. When exposed to bacteria
or bacterial antigen
s, Paneth cells secrete some of these compounds into the lumen
of the intestinal gland, thereby contributing to maintenance of the gastrointestinal barrier.
Paneth cells are named after Joseph Paneth
(1857–1890), Austrian physician.
s 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.
, also known as cryptidins. 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 membrane
s, 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
.
, tumor necrosis factor-alpha , and phospholipase A2
. Lysozyme and phospholipase A2 both 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 virus
es.
Enteroendocrine cells
Enteroendocrine cells are specialized endocrine cells of the gastrointestinal tract. They produce hormones such as serotonin, somatostatin, motilin, cholecystokinin, gastric inhibitory peptide, neurotensin, vasoactive intestinal peptide, and enteroglucagon....
, represent the principal cell types of the epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
of the small intestine. (A few may also be found sporadically in the cecum and appendix.) They are identified microscopically by their location just below the intestinal stem cells in the intestinal glands and the large eosinophilic
Eosinophilic
Eosinophilic refers to the staining of certain tissues, cells, or organelles after they have been washed with eosin, a dye.Eosin is an acidic dye; thus, the structure being stained is basic....
refractile granules that occupy most of their cytoplasm. These granules consist of several anti-microbial compounds and other compounds that are known to be important in immunity and host-defense. When exposed to bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
or bacterial antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
s, Paneth cells secrete some of these compounds into the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
of the intestinal gland, thereby contributing to maintenance of the gastrointestinal barrier.
Paneth cells are named after Joseph Paneth
Joseph Paneth
Joseph Paneth 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 ....
(1857–1890), Austrian physician.
Location
Paneth cells are found throughout the small intestine and the appendix at the base of the intestinal glands. Like the other epithelial cell lineages in the small intestine, paneth cells originate at the stem cell region near the bottom of the gland. However, unlike the other epithelial cell types, paneth cells migrate downward from the stem cell region and settle just adjacent to it. This close relationship to the stem cell region is thought to suggest that paneth cells are important in defending the gland stem cells from microbial damage, although their function is not entirely known.Function
Small intestinal crypts house stem cellCell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s 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
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
, and the location of Paneth cells adjacent to stem cells suggests that they play a critical role in defending epithelial cell renewal.
Sensing microbiota
Paneth cells sense bacteria via MyD88-dependent toll-like receptor (TLR) activation which then triggers antimicrobial action.http://www.pnas.org/content/105/52/20858.abstract?etocDefensins
The principal defense molecules secreted by Paneth cells are alpha-defensinsDefensin
Defensins are small cysteine-rich cationic proteins found in both vertebrates and invertebrates. They have also been reported in plants. They are, and function as, host defense peptides. They are active against bacteria, fungi and many enveloped and nonenveloped viruses. They consist of 18-45 amino...
, also known as cryptidins. 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 membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
s, 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
Lipopolysaccharide
Lipopolysaccharides , also known as lipoglycans, are large molecules consisting of a lipid and a polysaccharide joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria, act as endotoxins and elicit strong immune responses in animals.-Functions:LPS is the major...
, muramyl dipeptide
Muramyl dipeptide
Muramyl dipeptide is a peptidoglycan constituent of both Gram positive and Gram negative bacteria. It is composed of N-acetylmuramic acid linked by its lactic acid moiety to the N-terminus of an L-alanine D-isoglutamine dipeptide.-See also:* Dipeptide...
and lipid A
Lipid A
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 molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane...
.
Other secretions
In addition to defensins, Paneth cells secrete lysozymeLysozyme
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are glycoside hydrolases, enzymes that damage 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...
, tumor necrosis factor-alpha , and phospholipase A2
Phospholipase A2
Phospholipases A2 are enzymes that release fatty acids from the second carbon group of glycerol. This particular phospholipase specifically recognizes the sn-2 acyl bond of phospholipids and catalytically hydrolyzes the bond releasing arachidonic acid and lysophospholipids...
. Lysozyme and phospholipase A2 both have clear antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
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 virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es.