The mast cell plays a central role in the immune system of teleost fish.

The growing interest in fish models could raise an opportunity to better understand mast cell functions. The piscine mast cell, also known as eosinophilic granular cell, originates from haematopoietic organs, migrates to sites of maturation, and increases in injured tissues. Although there has been confusion arising from the different distribution in fish species and morphological and staining properties, there is a general agreement that the main functional roles, as those exploited in immunity, are quite similar. The aim of this review is to mainly focus on the roles of mast cells in teleost fish disease and in fish models of human diseases, with the attempt to give a comprehensive picture of their role in piscine immune function and their relationship to other immune system cells.