Fine Structure of the Human Palpebral Conjunctiva with Special Reference to the Pathological Changes in Vernal Conjunctivitis

Abstract

The normal human conjunctiva of the upper tarsal region and that affected by vernal conjunctivitis (untreated and hydrocortisone-treated) were observed with the electron microscope.1. The conjunctiva is lined with stratified columnar epithelium consisting of 2 to 3 layers of epithelial cells intermingled with a few goblet cells. The epithelial surface has considerably deep depressions which are called crypts or intracellular ductules.2. The epithelial cells show elaboration of small secretory granules of variable electron density in the cisternae of the Golgi apparatus. The granules are gathered around the crypts or ductules and discharge their contents through a small opening formed at the point of fusion between the limiting membrane of the granule and the surface plasma membrane. Such secretory activity of ordinary epithelial cells was accelerated in vernal conjunctivitis.3. Fine filaments which are abundant in the cytoplasmic matrix of the epithelial cells disappear in the cells of conjunctiva affected by vernal conjunctivitis. They reappear after treatment with hydrocortisone.4. The lamina propria of the conjunctiva is connective tissue rich in blood vessels and myelinated and unmyelinated nerve fibers. When the tissue is affected by vernal conjunctivitis, fine filamentous material may appear in the matrix either aggregated to form a large mass or infiltrating among collagen fibrils. These developments are considered the counterpart of hyaline degeneration seen with the light microscope as a peculiar characteristic of vernal conjunctivitis. Such a filamentous substance also accumulates in the intercellular spaces of the epithelium which widen as one of the pathological changes of vernal conjunctivitis.5. Various kinds of mesenchymal wandering cells occur especially in the lamina propria, but some of them infiltrate into the epithelial layer. Histiocytes, eosinophils, neutrophils, plasma cells and mast cells were recognized.6. Some plasma cells contained globules (Russell bodies) and crystalloids in the rough endoplasmic reticulum. The mast cell granules are highly variable in structure, viz., fingerprint-like, homogeneous, fine granulated or reticular. Mast cells having fine granulated or homogeneous granules are presumably ready to release histamine. These findings on the plasma cells and mast cells point out the allergic inflammation in the conjunctival interstitium.