Mast cells in the intestine and gills of the sea bream, Sparus aurata, exposed to a polychlorinated biphenyl, PCB 126.

The presence of mast cells has been reported in all classes of vertebrates, including many teleost fish families. The mast cells of teleosts, both morphologically and functionally, show a close similarity to the mast cells of mammals. Mast cells of teleosts, localized in the vicinity of blood vessels of the intestine, gills and skin, may play an important role in the mechanisms of inflammatory response, because they express a number of functional proteins, including piscidins, which are antimicrobical peptides that act against a broad-spectrum of pathogens. An increase in the number of mast cells in various tissues and organs of teleosts seems to be linked to a wide range of stressful conditions, such as exposure to heavy metals (cadmium, copper, lead and mercury), exposure to herbicides and parasitic infections. This study analyzed the morphological localization and abundance of mast cells in the intestine and gills of sea bream, Sparus aurata, after a 12, 24 or 72 h exposure to PCB 126, a polychlorinated biphenyl, which is a potent immunotoxic agent. In the organs of fish exposed to PCB 126, it was observed that in addition to congestion of blood vessels, there was extravasation of red blood cells, infiltration of lymphocytes, and a progressive increase in numbers of mast cells. These data confirm the immunotoxic action of PCB, and the involvement of mast cells in the inflammatory response.