Immunohistochemical demonstration of epithelial and urothelial antigens at the light- and electron microscope levels.

Antiserum raised in rabbits against the cytosol fraction from calf bladder epithelium was absorbed with sera, human erythrocytes and non-epithelial tissues until it became specific for a number of epithelia including urothelium, as demonstrated by immunofluorescence and immunoperoxidase techniques. Electron microscope immunocytochemistry showed that, in the urothelium, the majority of reaction product was present in the superficial cells in association with the plasma membrane, cytoplasmic membrane vesicles and cytoskeleton. After a second series of absorptions with epithelial organs other than bladder, the antiserum was rendered urothelium-specific and the strongest reaction was seen in superficial layer cells. Epithelium and urothelium specific antigens were species cross-reactive and could also be demonstrated in foetal and malignant urothelium. In malignantly transformed mouse bladder epithelium cell lines, the epithelial antigens were associated with the inner surface of the plasma membrane and underlying cytoskeletal elements.