- Mast Cells are a type of leukocyte present throughout the body's tissues which contain granules possessing vasoactive substances such as histamine and other inflammatory mediators. These cells can be induced to release their granules in response to certain stimuli and in doing so locally regulate vasculature and inflammation. Although Mast Cells likely evolved to protect against Helminthic infections, their importance is now primarily known in the pathogenesis of allergic responses.
- Mast Cells possess Fc Receptor for the IgE isotype of antibody as do the other anti-parasitic leukocytes, Basophils and Eosinophils. Unlike most Fc Receptors, the IgE Fc Receptor binds antibody even when it is not complexed with its antigen. When antigen is present, attachment to the Fc bound IgE is directly sensed by the Mast Cell which degranulates in response, thus releasing its vasoactive and inflammatory mediators. These inflammatory mediators also serve to recruit the other anti-parasitic leukocytes basophils and eosinophils. It is becoming increasingly clear that mast cells, basophils, and eosinophils are critical for host defense against large extracellular parasitic infections. Notably, IgE is the primary antibody isotype produced in response to parasitic infections. Furthermore, mast cells, basophils, and eosinophils can all release their granules into the extracellular space which would be required to attack large, multicellular organisms that cannot be phagocytosed.
- Mast Cells are derived from Hematopoietic Stem Cells in the bone marrow. Development of Mast Cells is more fully described as part of Hematopoiesis.
- Mast Cells must be detected with specialized stains and are characteristically packed with dense cytoplasmic granules representing stored histamine and other vasoactive mediators.