Response of eosinophilic granule cells of gilthead seabream ( Sparus aurata , Teleostei) to bacteria and bacterial products

Abstract

Eosinophilic granule cells in the gills and peritoneal exudate of gilthead seabream (Sparus aurata L.) are characterized by the presence of prominent eosinophilic granules in their cytoplasm and are here described for the first time. The oval granules of these cells contain an electron-dense inclusion surrounded by a less dense filamentous matrix and are peroxidase- and acid phosphatase-negative. Unlike other granulocytes of gilthead seabream, eosinophilic granule cells do not ingest bacteria in vivo. The intraperitoneal injection of extracellular products of Pasteurella piscicida induces mobilization of eosinophilic granule cells to the blood and other tissues and causes changes in their structure. Shortly after injection, the granules of eosinophilic granule cells become swollen and some fuse with the cell membrane. From 7 h post-injection, many eosinophilic granule cells in the gills degenerate and are then phagocytosed by macrophages, which are especially abundant after 24 h. From 24 h to 72 h, eosinophilic granule cells from the gills contain abundant autolysosomes together with granules of a normal morphology.

Immunocytochemical localization of piscidin in mast cells of infected seabass gill

“…This suggests that the gill is primed with the innate immune system, thus enabling immediate response to a pathogen [44,45]. Mast cells can occur throughout the loose connective tissue of the gill arch and some have suggested a resident population for these cells [36,46].…”

“…Recently it has been reported that histamine is stored in mast cells of Perciformes, the largest and most evolutionarily advanced order of teleosts [47]. It is well known that histamine regulates the Perciformes inflammatory response [46]. Investigations have shown that mast cells of gills and intestine are involved in the production of specific antimicrobial peptides, namely pleurocidin [11,36] and piscidin [12,13,48], suggesting that these cells are directly involved in killing microbes.…”

Mast cell responses to Ergasilus (Copepoda), a gill ectoparasite of sea bream

“…In S. aurata, MCs were documented inside, and/or in close proximity to capillaries and they were observed throughout the loose connective tissue of the gill arch. With reference to the presence of mast cells in loose connective tissue some authors have suggested a resident population for these cells [51,56].…”

Effects of administration of probiotic strains on GALT of larval gilthead seabream: Immunohistochemical and ultrastructural studies

“…IHC of the intestinal mucosa with the mAb G7 and eosin/MGG counterstaining also discriminated two main subpopulations of acidophilic granulocytes (E þ G7 þ and E þ G7 ÿ ), corroborating ultrastructural data. According to their localization and staining pattern E þ G7 ÿ granulocytes may represent the gilthead seabream EGCs [38] which do not exhibit phagocytic activity in vivo.…”