Mast cells contain a number of preformed chemical mediators such as histamine, chymase, carboxypeptidase and proteolytic tryptase. A substantial quantity of chymase is estimated to be found in mast cells of skin and lung and suggests this enzyme plays a major role in mast cell mediated events. Human mast cell chymase is considered to be an important marker of mast cells as well as an important mediator of inflammation.