What is a Mast Cell?

A cell, occurring in large numbers in the skin and respiratory and lymphatic systems, that plays a central part in allergic reactions. It is full of granules of powerfully irritating substances such as histamine, serotonin and heparin which are released to cause symptoms when allergens contact the cells.

Photo of cultured mast cells at 100X using an oil immersion lens and an olympus digital camera. The cells are stained with Tol Blue, and might appear slightly degranulated as they were activated using an artificial antigen during the course of an experiment.