Intermediate-filament expression in ocular tissue.

Intermediate-filament proteins (IFPs) occur in the intracellular cytoskeleton of eukaryotic cells, and their expression in diverse tissues is related both to embryology as well as to differentiation. Although the available information concerning their functional properties in vivo is still incomplete, antibodies against individual IFPs are commonly used in immunohistochemical procedures as markers for differentiation, and these antibodies are of outstanding value in the routine histopathological evaluation of tumor specimens. This review presents a compilation of the currently available data concerning IFP expression in normal and diseased ocular tissues. Representatives of every known class of IFP have been detected in normal ocular tissues. The external epithelia exhibit complex expression patterns of cytokeratin (CK) polypeptides, with CK3 and CK12 being specific markers of the corneal epithelium. Recent research has revealed that single mutant CK polypeptides may play a role in the pathogenesis of corneal dystrophies. The internal ocular epithelia reveal simple but specific patterns of IFP expression, these comprising simple-epithelial CKs and/or the mesenchymal IFP, vimentin. The IFP complement of the neuronal structures of the eye embraces several distinct IFP classes and reflects the diversity of the cell types present at these sites. With respect to ocular tumors, the IFP profile of melanomas might be correlated with metastatic potential. In conclusion, IFP analysis may be able to cast light on the pathogenesis of ocular diseases, as well as being a valuable adjunct in ophthalmopathological diagnosis.