Immunocytochemical localization of lysozyme in intestinal eosinophilic granule cells (EGCs) of Atlantic salmon, Salmo salar L.

Abstract

AbstractThe distribution of lysozyme in the intestine of Atlantic salmon, Salmo salar L., was studied by light‐ and electron‐microscopic immunocytochemistry. Eosinophilic granule cells (EGCs) in the subepithelial region of the lamina propria showed strong immunoreactivity to lysozyme, while epithelial cells were only occasionally stained. At the ultrastructural level, lysozyme was localized to secretary granules of EGCs, demonstrating features in common with the Paneth cell of the mammalian small intestine, previously shown to produce antibacterial substances such as lysozyme. Furthermore, EGCs stained positive with phloxine‐tartrazine, a histochemical stain that is used for identification of Paneth cells. This study reveals that EGCs show close resemblance to mammalian intestinal Paneth cells, and thus, may be important for the intestinal defense system in salmonid fish.