Abstract
Ultrastructural and immunohistochemical features of thymic epithelial reticular cells of ducks having formed intracellular or intercellular cysts were studied for their possible involvement in thymic secretion. A striking feature of elaboration, secretion and storage of a mucous substance, positive in periodic acid-Schiff (PAS) reaction was confirmed within the intracellular cyst of one of these cells, whereas no morphological evidence for secretion by the cell having formed an intercellular cyst was obtained. Furthermore, in the ducks immunized with horseradish peroxidase (HRP), antibody against HRP was detected in an area identical to that of the intracellular cyst as well as in the secretory granules of the epithelial reticular cells in intact ducks but not in bursectomized one. These morphological and immunohistochemical findings may suggest the secretory and storage activities of the thymic cyst-containing epithelial reticular cells in ducks.
