Peyer's patches
Encyclopedia
Peyer's patches are organized lymphoid nodules, named after the 17th-century Swiss anatomist Johann Conrad Peyer
. They are aggregations of lymphoid tissue that are usually found in the lowest portion of the small intestine
, the ileum
, in humans; as such, they differentiate the ileum from the duodenum
and jejunum
.
layer of the mucosa and extending into the submucosa of the ileum
.
In adults, B lymphocytes are seen to predominate in the follicles' germinal centers. T lymphocytes are found in the zones between follicles.
is exposed to the external environment, much of it is populated with potentially pathogen
ic microorganism
s. Peyer's patches thus establish their importance in the immune surveillance of the intestinal lumen and in facilitating the generation of the immune response within the mucosa.
Pathogenic microorganisms and other antigen
s entering the intestinal tract encounter macrophages, dendritic cell
s, B-lymphocytes, and T-lymphocytes found in Peyer's patches and other Mucosa Associated Lymphatic Tissue
(MALT).
Peyer's patches are covered by a special epithelium that contains specialized cells called microfold cells (M cells
) which sample antigen directly from the lumen and deliver it to antigen-presenting cells (located in a unique pocket-like structure on their basolateral side). B-cells and memory cells are stimulated upon encountering antigen
in Peyer's patches. These cells then pass to the mesenteric lymph nodes where the immune response is amplified. Activated lymphocytes pass into the blood stream via the thoracic duct
and travel to the gut where they carry out their final effector functions.
.
The hypertrophy of Peyer's patches has also been associated with susceptibility to transmissible spongiform encephalopathies (commonly known as prion diseases).
Salmonella hadar
and poliovirus also target this section of the intestine.
Johann Conrad Peyer
Johann Conrad Peyer was a Swiss anatomist who was a native of Schaffhausen. He studied medicine in Paris under Guichard Joseph Duverney , in Montpellier under Raymond Vieussens and received his medical degree in 1681 at Basel. Later he returned to Schaffhausen to practice medicine...
. They are aggregations of lymphoid tissue that are usually found in the lowest portion of the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
, the ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
, in humans; as such, they differentiate the ileum from the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
and jejunum
Jejunum
The jejunum is the middle section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms middle intestine or mid-gut may be used instead of jejunum.The jejunum lies between the duodenum...
.
Location and appearance
Peyer's patches are observable as elongated thickenings of the intestinal epithelium measuring a few centimeters in length. About 30 are found in humans. Microscopically, Peyer’s patches appear as oval or round lymphoid follicles (similar to lymph nodes) located in the lamina propriaLamina propria
The lamina propria is a constituent of the moist linings known as mucous membranes or mucosa, which line various tubes in the body ....
layer of the mucosa and extending into the submucosa of the ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
.
In adults, B lymphocytes are seen to predominate in the follicles' germinal centers. T lymphocytes are found in the zones between follicles.
Function
Because the lumen of the gastrointestinal tractGastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
is exposed to the external environment, much of it is populated with potentially pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
ic microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s. Peyer's patches thus establish their importance in the immune surveillance of the intestinal lumen and in facilitating the generation of the immune response within the mucosa.
Pathogenic microorganisms and other 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 entering the intestinal tract encounter macrophages, dendritic cell
Dendritic cell
Dendritic cells are immune cells forming part of the mammalian immune system. Their main function is to process antigen material and present it on the surface to other cells of the immune system. That is, dendritic cells function as antigen-presenting cells...
s, B-lymphocytes, and T-lymphocytes found in Peyer's patches and other Mucosa Associated Lymphatic Tissue
Mucosa-associated lymphoid tissue
The mucosa-associated lymphoid tissue is the diffusion system of small concentrations of lymphoid tissue found in various sites of the body, such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin.MALT is populated by lymphocytes such as T cells and B cells, as...
(MALT).
Peyer's patches are covered by a special epithelium that contains specialized cells called microfold cells (M cells
M cells
M cells are cells found in the follicle-associated epithelium of the Peyer's patch. They transport organisms and particles from the gut lumen to immune cells across the epithelial barrier, and thus are important in stimulating mucosal immunity.Unlike their neighbouring cells, they have the unique...
) which sample antigen directly from the lumen and deliver it to antigen-presenting cells (located in a unique pocket-like structure on their basolateral side). B-cells and memory cells are stimulated upon encountering 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...
in Peyer's patches. These cells then pass to the mesenteric lymph nodes where the immune response is amplified. Activated lymphocytes pass into the blood stream via the thoracic duct
Thoracic duct
In human anatomy, the thoracic duct of the lymphatic system is the largest lymphatic vessel in the body. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal....
and travel to the gut where they carry out their final effector functions.
Pathology
Although important in the immune response, excessive growth of lymphoid tissue in Peyer's patches is pathologic, as hypertrophy of Peyer's patches has been closely associated with idiopathic intussusceptionIntussusception (medical disorder)
An intussusception is a medical condition in which a part of the intestine has invaginated into another section of intestine, similar to the way in which the parts of a collapsible telescope slide into one another. This can often result in an obstruction...
.
The hypertrophy of Peyer's patches has also been associated with susceptibility to transmissible spongiform encephalopathies (commonly known as prion diseases).
Salmonella hadar
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
and poliovirus also target this section of the intestine.