The Role of Mast Cells

Published 12/15/2013. Updated 1/4/2014.

Mast cells, located in our skin and mucosa, are an essential part of our immune defenses. These unique cells are tasked with activating our immune systems to defend us from harmful invaders. Mast cells commonly reside at the body’s various borders, where they act as goalies to defend us against pathogens trying to gain entry.
Mast cells also live in the linings of our stomachs and intestines, in connective tissues – including the skin, where they promote wound healing – and elsewhere in our bodies.
Inside the mast cells are tiny granules containing a variety of chemicals, called mediators, that activate our immune systems to defend us from harmful invaders. An example: When mast cells perceive a breach in our skin they sound the alarm, releasing histamine to send troops to the wound site. The itching you feel around a healing scab is probably caused by histamine released by mast cells gathered there to promote healing. It is also believed that mast cells have a role in angiogenesis, the growth of new blood vessels. (MastCellAware.com, 2012-2013)
The mast cells’ mediator chemicals are divided into three major groups. You have probably heard of some of the neurochemicals  in each group:
Preformed mediators: Histamine, serotonin, proteoglycans, tryptases and other proteases
Newly synthesized lipid mediators: Prostaglandins, cysteinyl leukotrienes, platelet activating factor
Cytokines and chemokines: Interleukin-4, interleukin-5, TNF-alpha, TGF-beta, chemokines (Gurish & Castells, 2013)
We require mast cells in order to survive. Without them we would be defenseless against pathogenic invaders. No person without any mast cells has ever been found.
 However, if too many of these nifty cells get activated at the same time or they proliferate wildly, unpleasant symptoms and disorders result. See My Own Struggle with Mast Cells Gone Wild for an example.
An extreme form of mast cell disregulation is Systemic Mastocytosis (in which the body over produces mast cells in multiple organs, including bone marrow) and a serious condition called Mast Cell Activation Syndrome (where a trigger activates even a normal number of mast cells to release their mediators too easily) results.
In Systemic Mastocytosis, these mediators can cause a range of symptoms in children and adults, including shortness of breath, low blood pressure, hives and swelling, itching, nausea and vomiting, diarrhea, fainting, headache, uterine cramps and bleeding, skin rashes, flushing, abdominal pain, bloating, musculoskeletal pain and lesions and anaphylaxis. These symptoms can be triggered by heat, cold, physical or emotional stress, perfumes or other odors, medications, insect stings and foods. (American Academy of Allergy, Asthma and Immunology, 2013) (Mastocytosis Society, 2011)
Even when mast cells are not so wildly out of control, their over activation can cause much misery. They have historically been considered useful first responders in microbial infections. And they play a role as potent contributors to allergic reactions. Continuing research into mast cells is revealing that mast cell involvement can worsen some conditions, disorders and diseases.

Mast Cells at Work in the Internal Elastic Lamina (a layer of elastic tissue inside veins and arteries)

ALLERGIC REACTIONS AND AUTOIMMUNE DISEASES
Mast cells are the primary responders to minute amounts of otherwise harmless substances the immune system regard as allergens. The resulting battle results in various allergic reactions – such as asthma, eczema, itches, allergic rhinitis and allergic conjunctivitis.  Research is finding they also play a key role in the early phases of the various autoimmune diseases – such as rheumatoid arthritis. (Benoist & Mathis, 2002)
ANAPHLAXIS
Anaphylaxis is a systemic overreaction to things like nuts, bee stings, shellfish, latex and some drugs. Mast cells begin degranulating (releasing their contents) when an allergen is detected. An anaphylactic reaction can begin immediately on exposure and rapidly progress to airway constriction, skin and intestinal irritation, and altered heart rhythms. Severe anaphylaxis can result in a complete inability to breathe, shock and death.  (Mayo Clinic, 2013)
REPRODUCTIVE DISORDERS
Mast cells exist within the endometrium, with increased activation and release of mediators in endometriosis. In males, mast cells are present in the testes and are increased in oligo- and azoospermia, with mast cell mediators directly suppressing sperm motility.
MAST CELL TUMORS
In the less serious form of Mastocytosis, proliferation of mast cells in the skin, mast cell tumors are produced. They are often seen in elderly dogs and cats and can become quite large. Though often not malignant, they have the potential to be. Mast cell tumors can also grow on humans. (MastCellAware.com, 2012-2013)
 There is a long list of other conditions and diseases where mast cells also appear to play a significant role: Autism, breast cancer, fibromyalgia, interstitial cystitis, Crohn’s disease, dysautonomia, heart failure, brain inflammation, mixed organic brain syndrome, multiple sclerosis, multiple myeloma, postural orthostatic tachycardia syndrome (POTS) and more. (MastCellAware.com, 2012-2013)
Also see My Own Struggle  with Mast Cells Gone Wild for my personal experience with what can happen when these useful cells grossly over proliferate.
REFERENCES

American Academy of Allergy, Asthma and Immunology. (2013). Systemic Mastocytosis. See http://www.aaaai.org/conditions-and-treatments/related-conditions/systemic-mastocytosis.aspx

Benoist, C. & Mathis, D. (2002). Mast cells in autoimmune disease. Nature, 420, 875-878.

Gurish, M. & Castells, M.C. (2013). UpToDate, Mast cell derived mediators. See http://www.uptodate.com/contents/mast-cell-derived-mediators

MastCellAware.com.(2012-2013). The Good, The Bad & The Ugly: What are mast cells and why should we care about them? See http://www.mastcellaware.com/about.html

The Mastocytosis Society, Inc.(2011). See http://www.tmsforacure.org/welcome.php

Mayo Clinic. (2013). Anaphylaxis.See http://www.mayoclinic.com/health/anaphylaxis/DS00009

 

A version of this page content will appear in my forthcoming 2014 Oriental Medicine Journal article THE MICROBIOTA-GUT-BRAIN AXIS: The constant two-way communication between our guts and our brains.

 

© Copyright 2013-2014 Joan Rothchild Hardin. All Rights Reserved.

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