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.