Histology and ultrastructure of the the harderian glands - accessory lacrimal gland - of the chicken.

The Harderian gland is an exocrine gland located in the orbit of the chicken. In the stroma of the folds, an extreme amount of plasma cells can be observed. Electron-microscopic observations revealed that the surface epithelium over the margin of the folds is joined up to deeper epithelial cells with processes rich in tonofibrils and the space among them is filled with plasma cells. The basement membrane separating the surface epithelium from the underlying connective tissue is lacking in these areas, therefore, plasma cells are in direct contact with epithelial cells. A fine network of reticular fibrils can be found inside the folds and reticulum cell-like elements with long processes are intercalated among the plasma cells. This morphology resembles that of the lymphoepithelial organs. Based on this similarity the lymphoepithelial character and a possible immunological function of the Harderian gland is supposed.