Intermediate filaments in the human retina and retinoblastoma. An immunohistochemical study of vimentin, glial fibrillary acidic protein, and neurofilaments

Fifty-five retinoblastoma specimens were studied by a sensitive immunoperoxidase method to determine the intermediate filament types present in human retina and retinoblastoma. Polyclonal antiserum against vimentin and monoclonal antibodies to glial fibrillary acidic protein (GFAP) and to the 200 kD neurofilament triplet protein were used. In the human retina, Müller's cells coexpressed vimentin and GFAP in most instances, probably as a reactive phenomenon. Surprisingly, the horizontal cells did not stain with any of the antibodies used, and may thus lack intermediate filaments. Also, the meshwork of neural fibers in the inner plexiform layer was unusually sparse. Retinoblastoma cells were found to be devoid of all intermediate filament types studied. The tumors contained, however, vimentin and GFAP in the stromal cells. All neurofilament-positive cells in retinoblastoma apparently derived from infiltrated retina. One retinoblastoma eye was also studied by indirect immunofluorescence microscopy of frozen sections with identical results.