Mucosa-associated lymphoid tissue (MALT)
A loosely organized collection of LYMPH tissue that underlies and integrates with epithelial tissue (the lining of mucous membranes) throughout the body. MALT reinforces the body’s immune presence and response in areas of the body that provide direct interface with the external environment. These areas, such as the gastrointestinal tract and the LUNGS, are most vulnerable to breaches that could allow pathogens to enter the body to cause INFECTION.
MALT contains clusters of phagocytic cells such as macrophages and dendritic cells, which consume cellular debris, as well as T-cell lymphocytes and B-cell lymphocytes. T-cell lymphocytes attack and kill invading pathogens, and B-cell lymphocytes produce antibodies to protect against future invasion by the same pathogens. There are several types of MALT; each has specific functions, according to its location in the body. Among them are
- BRONCHUS-ASSOCIATED LYMPHOID TISSUE (BALT), which strengthens the body’s defense against INFLUENZA and PNEUMONIA
- GUT-ASSOCIATED LYMPHOID TISSUE (GALT), which helps protect against invasion by gastrointestinal viruses
- NOSE-ASSOCIATED LYMPHOID TISSUE (NALT), which intensifies the body’s resistance to airborne viruses such as those that cause COLDS
- SKIN-ASSOCIATED LYMPHOID TISSUE (SALT), which helps block BACTERIA, fungi, and other pathogens from passing through microscopic breaks in the SKIN
- VASCULAR-ASSOCIATED LYMPHOID TISSUE (VALT), which infiltrates the epithelium of the BLOOD vessels
MALT may be the site of solid tumors that develop in LYMPHOMA (sometimes called MALT lymphoma). The most common MALT site for such an occurrence is the gastrointestinal tract. Researchers believe these lymphomas develop when a constant assault, such as a persistent infection, engages the MALT site. B-cell lymphocytes accumulate to fight the infection. When their accumulation persists over time, which is abnormal, the B-cell lymphocytes turn cancerous. The connection with MALT lymphomas that arise from GALT is HELICOBACTER PYLORI infection, which also has a strong connection to STOMACH CANCER. Researchers believe H. pylori may account for 85 percent or more of gastrointestinal MALT lymphomas, many of which grow in the STOMACH. Treatment is highly successful when the diagnosis of MALT lymphoma occurs early in the CANCER’s development because the tumors grow slowly and lack aggression in spreading.
For further discussion of MALT within the context of the structures and functions of the immune system, please see the overview section “The Immune System and Allergies.”
See also ANTIBODY; B-CELL LYMPHOCYTE; FUNGUS; LYMPHOCYTE; MACROPHAGE; METASTASIS; MONONUCLEAR PHAGOCYTE SYSTEM; PATHOGEN; PHAGOCYTE; PHAGOCYTOSIS; T-CELL LYMPHOCYTE; VIRUS.
