IMMUNOCYTOCHEMICAL LOCALIZATION OF LYSOZYME IN INTESTINAL EOSINOPHILIC GRANULE CELLS (EGCS) OF ATLANTIC SALMON, SALMO-SALAR L

The distribution of lysozyme in the intestine of Atlantic salmon, Salm o salar L., was studied by light- and electron-microscopic immunocytoc hemistry. Eosinophilic granule cells (EGCs) in the subepithelial regio n of the lamina propria showed strong immunoreactivity to lysozyme, wh ile epithelial cells were only occasionally stained. At the ultrastruc tural level, lysozyme was localized to secretory granules of EGCs, dem onstrating features in common with the Paneth cell of-the mammalian sm all intestine, previously shown to produce antibacterial substances su ch as lysozyme. Furthermore, EGCs stained positive with phloxine-tartr azine, a histochemical stain that is used for identification of Paneth cells. This study reveals that EGCs show close resemblance to mammali an intestinal Paneth cells, and thus, may be important for the intesti nal defence system in salmonid fish.