Mast Cells

A type of white blood cell (immune cell) commonly found in various connective tissues throughout the body like beneath skin, close to blood and lymph vessels, as well as in nerve, lung tissue, and intestinal tissue. They control many immune responses such as the response to bacteria, parasites, and allergens (per National Cancer Institute)

Source:

National Cancer Institute

https://www.cancer.gov/publications/dictionaries/cancer-terms/def/mast-cell