http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3395887/
Mast cells are primitive immune cells that appear early in evolution and have since evolved into multifunctional cells in vertebrates.1 They have been long recognized as initiators of IgE-dependent allergic diseases but it is now realized that they also play a fundamental role in innate and adaptive immune responses to infection as well as inflammatory autoimmune diseases.2–4 In addition, there is evidence that mast cells participate in inflammatory responses to incipient tumors which may either facilitate or retard tumor growth depending on the type of cancer.5–7 Other suspected non-immunological roles for mast cells include promotion of angiogenesis, tissue remodeling, and wound healing.8–11 As such, mast cells occupy a precarious position in that their responses to endogenous and exogenous stimuli can be detrimental as well as beneficial to the host.