Mast Cells (Mastocytes)

What are they?

Mast cells, or mastocytes, are part of the immune response to allergens and other chemical stimuli. There are two types of mast cells:those found in connective tissue and those found in the lining of mucous membranes. Both types of mast cells originate from a CD34+ cell in the bone marrow. ^1,3

What is the function of mast cells?

Part of the immune response system, mast cells contain cytoplasmic granules. When stimulated these granules engage in a process called degranulation, whereby cytokines and chemokines related to the inflammatory response are released. Several mechanisms can cause this degranulation, including physical factors such as heat, radiation, and trauma; chemical factors such as poisons, toxins and venoms; and immunoglobin E dependent or independent immune pathways, also known as the allergic response mechanism. ²

Upon degranulation, histamine is released into the extracellular environment along with proteoglycans such as heparin and serine proteases. These compounds work together to recruit other immune response cells to promote healing as well as produce a classical immune response: heat, swelling, redness and itchiness.

Why study mast cells?

Mast cells activate pathways that induce allergic reactions and inflammation such as arthritis. Mast cells play a role in eczema, asthma, allergic rhinitis and conjunctivitis. Two ways to treat these reactions are through antihistamines, which block histamine release post degranulation, or through a calcium channel block required for degranulation that prevents mast cells from degranulating. ³

Studies are ongoing to determine whether mast cells play a role in autoimmune disorders such as rheumatoid arthritis, multiple sclerosis, and lupus. Mastocytosis is a disorder whereby a significant increase in mast cells are found throughout the body ⁴. Mastocytosis can cause skin lesions, low blood pressure, bone and muscle pain as well as abdominal discomfort.