Unlike basophils, masts cell circulate in an immature form, maturing only in tissue sites where they are resident. They are long-lived cells, able to survive for months or years. At the earliest stages of infection, mast cells are important for communicating the presence of a pathogen to many cell types located nearby. Mast cells are well known to have a role in allergy and anaphylaxis, but are also found to be involved in wound healing, angiogenesis and immune tolerance.
Mast cells express a high-affinity receptor (FcεRI) for the Fc region of IgE, the least-abundant member of the antibodies and as a result mast cells are coated with IgE. When they encounter the antigen specific for the antibody mast cells are stimulated to release the contents of their granules (process known as degranulation) which is what causes the symptoms of allergy.