what are mast cells

Mast cells are immune cells that are derived from the myeloid lineage and are present in connective tissues throughout the body. They 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. Mast cells are oval or irregularly shaped cells that contain many small secretory granules, ranging in size from 0.2 to 0.8 micrometers. These granules are often so dense as to obscure the nucleus. Mast cells are mononuclear cells, and under light microscopy, a dense granular cytoplasm is seen, often obscuring the nucleus and other organelles. When it can be visualized, the nucleus is central, and the cell is mononuclear. Mast cells are important cells of the immune system and are of the hematopoietic lineage. They are originated from pluripotent progenitor cells of the bone marrow, 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. Mast cells have the capacity to release a multitude of pro-inflammatory mediators, and their activation and degranulation significantly modulate many aspects of physiological and pathological conditions in various settings.