Allergies and The Dark Knight of Our Immune System

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Mast cells are part of our immune system’s arsenal against microbial pathogens, parasites, viruses and some venoms.

The protective mast cell can also be involved in allergic reactions.

Mast Cells: Mighty Protector

Mast cells are found in our connective tissues such as the skin, and the linings of the stomach and intestines. They sound a chemical alarm when our body is threatened by disease. The alarm summons other disease fighting cells to threatened areas of the body.

Since mast cells congregate around wounds, they are also believed to facilitate tissue healing. The itch we often experience as a scab forms may be caused by mast cells releasing the compound histamine.

Research suggests still another role for mast cells – they may play a part in the growth of blood vessels. Since no living person with too few mast cells has ever been found, it might be that people with too few mast cells cannot survive.

Yet, for all their good works, mast cells can be an immune system stinker.

Mast Cells: Allergy Instigator

Within mast cells are granules (storage sacs) that contain chemicals such as histamine that trigger tissue inflammation. If a person has an overabundance of mast cells or they function improperly, they can cause problems.

These cells have a starring role in skin and mucosal allergic reactions, including asthma, eczema and itching from a variety of causes. A body-wide mast cell release of toxic molecules can cause anaphylaxis.

Mast-instigated allergic reactions occur when:

  • A bit of allergen, such as peanut protein, docks on the surface of a mast cell and activates resident IgE antibodies on the cell’s surface.
  • The mast cells then “de-granulate,” or release their sacs of histamine, tryptase and other inflammatory chemicals into the body.
  • Either a localized or a system-wide allergic reaction follows.

Mast cells are a good example of the proverbial “double-edged sword.” It seems that we cannot live without them, yet sometimes living with them makes life more difficult and occasionally dangerous.

Sources: Mast Cell Aware; World Allergy Organization Photo credit: Weilcome Images; / flickr creative commons.

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