Heterogeneity in the immunolocalization of cytokeratin specific monoclonal antibodies in the rat eye: evaluation of unusual epithelial tissue entities.

The immunocytochemical localization of cytokeratin and vimentin in rat eye tissues was investigated using a panel of 39 monoclonal antibodies specific for single or multiple of cytokeratin polypeptides and one polyclonal anti CK20 antiserum. The retinal and the ciliary body pigment epithelial only expressed cytokeratins 8 and 18, whereas the fetal retinal pigment epithelium and focally the adult epithelium, in the transition zone of retina and ciliary body, exhibited a reactivity for cytokeratin 19. In contrast, the non-pigmented ciliary epithelium was positive for vimentin only. In the rat conjunctiva distributed goblet cell clusters were selectively stained with cytokeratin 7, 8, 18 and 19 specific monoclonal antibodies. Among them a group of cytokeratin 8 and 18 specific monoclonal antibodies which stained the goblet cells as well as cytokeratin 8 and 18 positive internal controls did not react with either the cytokeratin 8 and 18 positive neuroectodermal cells of the rat eye nor the rat choroid plexus epithelium. This indicates differences in the phenotype e.g. conformational epitope changes, of neuroectodermal derived and other cytokeratins. The corneal and conjunctival epithelium showed a more complex distribution of squamous epithelium type cytokeratins. The limbal region as a transient zone connecting both epithelia exhibited a changing cytokeratin pattern. In general, the study emphasized the necessity to work with an enlarged antibody panel to avoid misleading results in the immunolocalization of cytokeratins.