Mucosa-Associated Lymphoid Tissue (MALT)

What is mucosa-associated lymphoid tissue (MALT)?

Mucosa-associated lymphoid tissue (MALT) are tissues that are part of your immune system. Areas of MALT have high concentrations of germ-fighting white blood cells (lymphoid tissues are areas of your body containing white blood cells) and are found throughout your mucous membranes (mucosa). Mucous membranes connect the inside and outside of your body, like your respiratory, digestive, urinary and reproductive tracts. Immune cells in MALT are often the first to encounter harmful germs (pathogens) and start an immune response to fight them off.

Specific MALTs include your tonsils, adenoids and Peyer’s patches (areas of your small intestine). Your appendix is also MALT — despite the common misconception that it has no purpose.

What percent of lymphoid tissue contains MALT?

MALT is a large part of your immune system: about 50% to 70% of your immune cells are in MALTs.

How do mucosa-associated lymphoid tissues (MALT) work?

Immune cells in MALTs trap foreign particles (like germs) and determine whether they might be harmful. They can destroy them and call other immune cells to the area to alert them to harmful intruders.

The immune cells in MALTs look for labels (antigens) on the outside of germs and other invaders. This is called antigen sampling. It determines whether they’ve found harmful invaders and if they’ve seen this specific germ before. Innate immune cells attack anything that’s not part of your body. B cells and T cells look for specific germs that they know how to attack. Your immune cells fight harmful germs before they can cause an infection (make you sick) and alert the rest of your immune system to come in and help fight.

Oral and nasal vaccines are an example of MALTs at work. The antigens in the vaccine quickly encounter immune cells in your nose and throat. The immune cells in MALTs alert other immune cells to remember the antigens for future infections.

Where are mucosa-associated lymphoid tissues (MALT) in your body?

MALTs are located in your mucous membranes (mucosa), which include your eyes, ears, nose, mouth and respiratory, digestive, urinary and reproductive tracts. These areas open to the outside and are the first to come in contact with germs that can infect you.

Specific types of MALT are categorized based on where they are in your body, including:

• Bronchus-associated lymphoid tissue (BALT)
• Conjunctival-associated lymphoid tissue (CALT)
• Gut-associated lymphoid tissues (GALT) — these include your tonsils, Peyer’s patches and appendix
• Nasal-associated lymphoid tissue (NALT) — sometimes, adenoids and tonsils are considered NALTs
• Vulvovaginal-associated lymphoid tissue (VALT)

Of these, gut-associated lymphoid tissues are the most well-understood.

What cells are in MALTs?

Areas of MALT contain high concentrations of immune cells, including:

• Innate immune cells: Macrophages and dendritic cells destroy germs and display antigens on their surface for adaptive immune cells to recognize.
• Adaptive immune cells: B cells and T cells can recognize specific antigens and fight them off more quickly than your innate immune cells.
• M cells (microfold cells): M cells take in and transport antigens to other immune cells.

What conditions affect mucosa-associated lymphoid tissue?

Conditions that affect MALTs include:

• Appendicitis
• Appendix cancer
• Bacterial infections
• Intussusception (enlarged Peyer’s patches can lead to an intestinal blockage)
• MALT lymphoma
• Tonsilitis
• Tonsil stones

What are signs or symptoms of MALT conditions?

Symptoms of conditions that affect MALTs depend on where in your body the issue is. Some symptoms could include:

• Fever
• Severe abdominal pain
• Sore throat
• Nasal congestion
• Unexplained weight loss

What tests check for MALT conditions?

Common tests your provider might use to diagnose issues with MALTS include:

• Blood tests: Your provider can look at your white blood count or perform antibody tests to look for infections and check the health of your immune system.
• Throat or nasal swabs: Your provider can use a swab to perform a bacterial culture.
• Imaging: Depending on where your symptoms are located, your provider might get an ultrasound, X-ray or CT scan.
• Biopsy: Your provider can take a sample of tissue to diagnose cancer or tissue changes.

What are treatments for MALT conditions?

Treatments vary depending on the condition. They could include:

• Antibiotics
• Surgery (like an appendectomy or tonsillectomy)
• Radiation or chemotherapy for cancers affecting MALTs