The mucosa-associated lymphoid tissue (MALT), also called mucosa-associated lymphatic tissue, is a diffuse system of small concentrations of

lymphoid tissue The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid o ...

found in various submucosal membrane sites of the

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

, such as the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...

nasopharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struct ...

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

breast The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues. In females, it serves as the mammary gland, which produces and secret ...

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

salivary gland The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gla ...

s, eye, and

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

. MALT is populated by lymphocytes such as

T cell A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell r ...

s and

B cell B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or ...

s, as well as

plasma cell Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B lymphocytes and secrete large quantities of proteins called antibodies in response to being presented specific substan ...

s and

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

s, each of which is well situated to encounter antigens passing through the mucosal epithelium. In the case of intestinal MALT, M cells are also present, which sample antigen from the lumen and deliver it to the lymphoid tissue. MALT constitute about 50% of the lymphoid tissue in human body.

Immune responses An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...

that occur at

mucous membranes A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

are studied by

mucosal immunology Mucosal immunology is the study of immune system responses that occur at mucosal membranes of the intestines, the urogenital tract, and the respiratory system. The mucous membranes are in constant contact with microorganisms, food, and inhaled ...

Categorization

The components of MALT are sometimes subdivided into the following: * GALT (

gut-associated lymphoid tissue Gut-associated lymphoid tissue (GALT) is a component of the mucosa-associated lymphoid tissue (MALT) which works in the immune system to protect the body from invasion in the gut. Owing to its physiological function in food absorption, the mucosa ...

Peyer's patches Peyer's patches (or aggregated lymphoid nodules) are organized lymphoid follicles, named after the 17th-century Swiss anatomist Johann Conrad Peyer. * Reprinted as: * Peyer referred to Peyer's patches as ''plexus'' or ''agmina glandularum'' (c ...

are a component of GALT found in the lining of the small intestines.) * BALT ( bronchus-associated lymphoid tissue) * NALT ( nasal-associated lymphoid tissue) * CALT (conjunctival-associated lymphoid tissue) * LALT (larynx-associated lymphoid tissue) * SALT (skin-associated lymphoid tissue) * VALT (vulvo-vaginal-associated lymphoid tissue) * TALT (testis-associated lymphoid tissue) It can be also distinguished by level of organization of the tissue: * O-MALT (organized mucosa-associated lymphatic tissue); specifically, the tonsils of

Waldeyer's tonsillar ring Waldeyer's tonsillar ring (pharyngeal lymphoid ring, Waldeyer's lymphatic ring, or tonsillar ring) is a ringed arrangement of lymphoid organs in the pharynx. Waldeyer's ring surrounds the naso- and oropharynx, with some of its tonsillar tissue l ...

are O-MALT.

Gray's Anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter, and first published in London in 1858. It has gone through multiple revised editions and the current edition, the 42nd (Octob ...

, 38ed. p. 1442 ff. * D-MALT (diffuse mucosa-associated lymphatic tissue); MALT that is not organized as a separately macroscopically anatomically identifiable mass, tissue or organ (such as the aforementioned O-MALT) is diffuse MALT.

Role in disease

MALT plays a role in regulating mucosal

immunity Immunity may refer to: Medicine * Immunity (medical), resistance of an organism to infection or disease * ''Immunity'' (journal), a scientific journal published by Cell Press Biology * Immune system Engineering * Radiofrequence immunity desc ...

. It may be the site of

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...

s, usually a

non-Hodgkin lymphoma Non-Hodgkin lymphoma (NHL), also known as non-Hodgkin's lymphoma, is a group of blood cancers that includes all types of lymphomas except Hodgkin lymphomas. Symptoms include enlarged lymph nodes, fever, night sweats, weight loss, and tiredness. ...

. A specific entity is the

marginal zone B-cell lymphoma Marginal zone B-cell lymphomas, also known as marginal zone lymphomas (MZLs), are a heterogeneous group of lymphomas that derive from the malignant transformation of marginal zone B-cells. Marginal zone B cells are innate lymphoid cells that no ...

(a subtype of which is termed MALT lymphoma). Certain subtypes of marginal zone B cell lymphomas such as those occurring in the stomach are commonly caused by ''

Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is though ...

'' infection. Peyer's Patches, groupings of lymphoid follicles in the mucus membrane, monitor the GALT closely to regulate pathogens that traverse through the area. Due to function of M cells in Peyer's Patches, adherence and transport of antigens across a single layer of epithelial cells, it's likely that dysfunction in these structures allow and entry point to pathogens.

References

External links

MALT resource page
- Patients Against Lymphoma

{{lymphatic system Lymphoid organ