Introduction A hallmark feature of mast cells from all species is their strong metachromatic staining with various cationic dues, such as Toluidine blue. These properties have been used since the late 19th century to identify mast cells as such (1). The biochemical background for the

Introduction The most striking morphological feature of mast cells is their numerous cytoplasmic secretory granules. These are filled with preformed compounds (“mediators”), which are rapidly released when mast cells are activated in a way that causes their degranulation. The preformed mediators encompass numerous different substances,