Mast cells are cells found in connective tissue throughout our bodies as part of our immune system. Mast cells are particularly prominent in tissues of our bodies that interact with our external world, such as those found on our skin and in our respiratory and digestive tracts. Mast cells can also be found in the organs and tissue of our circulatory and nervous systems. Mast cells play an important role in protecting our health by providing a line of defense against pathogens.

Mast Cell Functions

In response to exposure to a perceived pathogen, mast cells set off a rapid inflammatory response to outside invaders, such as germs, viruses, and parasites. Mast cells have the capacity to directly kill these organisms or to stimulate the production and release of substances that will destroy the pathogen.

Mast cells play a prominent role in the activation of the allergy response. When a person has an allergy, mast cells are responding to harmless triggers as if they were a threat.

In addition to their protective and immune system effects, mast cells are also involved in:

  • Homeostasis of blood vessels and bronchial functioningInjury healingFormation of new blood vesselsRegulate functioning of cells throughout the bodyRegulation of bone growth

Mast Cell Response

In response to a perceived threat, mast cells trigger a release of a variety of immune system mediators, such as histamine and serotonin, and enzymes such as cytokines and proteases. These substances result in both rapid and longer-term inflammatory responses. Let’s take a look at some of the more common mast cell responses.

Gastrointestinal tract response

When we eat something that is perceived to be harmful, mast cells will trigger a response that has the following effects:

  • Increased fluid secretionIncrease muscle contraction within the digestive system (may result in vomiting or diarrhea)Move fecal matter more quickly through the colon

These actions make sense, don’t they? The body is trying to get rid of what it perceives to be harmful as quick as it can.

Mast cells play an important role in promoting a healthy balance of the bacteria that make up our gut flora. As mast cells are found throughout the lining of our gut, they play a role in destroying and protecting our bodies from any pathogenic bacteria.

Respiratory tract response

Mast cells are found throughout the lining of our respiratory tracts. In response to an antigen, typically one that is inhaled, mast cells will trigger an immune response that includes:

  • Constriction of our airwaysCongestionCoughingIncreased production of mucus

As you can see from the above effects, it is not surprising that mast cells are highly involved in the symptoms of allergic asthma.

Skin response

You are probably familiar with the notion that some people experience hives or a rash in response to eating a certain food. This happens because antigens in the food enter the blood through the GI tract. As they circulate through the body they come into contact with mast cells found in the tissues of the skin. The inflammatory response of these mast cells can result in swelling, hives, rashes and the more chronic problem of atopic dermatitis (eczema).

Mast Cells and Digestive Disease

Due to the fact that mast cells line the intestinal tract, and given their effects in terms of an immune response, mast cells have been implicated in playing a role in the following two gastrointestinal diseases:

  • Food allergy
  • Irritable bowel syndrome (IBS)

The effects of mast cells can result in the following symptoms:

  • Fast transit of stool (resulting in diarrhea)
  • Increased fluid secretion in the large intestine (also contributing to diarrhea)
  • Visceral hypersensitivity (leading to abdominal pain)

Interestingly, the actions of mast cells can be influenced by the amount of stress you are under. There appears to be two-way communication between the cells of your nervous system and mast cells. Thus the actions of mast cells may play a primary role in the fact that IBS symptoms can be worsened by external stress.

Studies have shown that there is an increased number of mast cells in the intestinal lining of individuals who have IBS. Scientists do not yet know a lot about why this is so, but it is an exciting area of research as it leads to the possibility of the development of new effective treatments for the disorder.