Mast cell
Mast cells are big cells with rough metachromatic granula that contain lots of mediators of an allergic reaction, e.g. heparin, metabolites of arachidon acid (prostaglandin D2, leukotrienes). Primary effector cells of the immediate allergic reaction. Mast cells are found in the loose connective tissue of skin, lungs, gastrointestinal tract, and other tissues.