Mast cells are immune cells of the myeloid lineage that are present in connective tissues throughout the body. They are involved in regulating a variety of physiological functions, including vasodilation, angiogenesis, bacterial and parasite elimination, and venom detoxification. Mast cells are known to regulate vasodilation, vascular homeostasis, innate and adaptive immune responses, angiogenesis, and venom detoxification. They also play an important role in inducing the inflammatory cascade and are associated with many pathologies, including type I hypersensitivity reactions, mastocytosis, mast cell activation syndrome, and urticaria. Some key functions of mast cells include:

• Inflammatory response: Mast cells are long-lived tissue-resident cells with an important role in many inflammatory settings including host defense to parasitic infection and in the activation of the allergy response.

• Immune response: Mast cells are important cells of the immune system and are of the hematopoietic lineage. They regulate functions of many cell types, such as dendritic cells, macrophages, T cells, B cells, fibroblasts, eosinophils, endothelial cells, and epithelial cells.

• Mediator release: Mast cells generate and release multi-potent molecules, such as histamine, proteases, prostanoids, leukotrienes, heparin, and many cytokines, chemokines, and growth factors. These mediators can cause inflammation and other physiological responses.

• Pathogen defense: Mast cells are well placed to serve as immune sentinel cells to both respond directly to pathogens and send signals to other tissues to modulate.

Mast cells are derived from the myeloid lineage and mature under the influence of the c-kit ligand and stem cell factor in the presence of other distinct growth factors provided by the microenvironment of the tissue where they are destined to reside.