Cytokeratin patterns of tissues related to cholesteatoma pathogenesis.

Specimens of cholesteatoma matrix, meatal epidermis, and middle ear epithelium were removed during surgery, and immunohistochemical techniques were used to investigate cytokeratin expression. The use of five chain-specific anticytokeratin monoclonal antibodies and one broad specific anticytokeratin monoclonal antibody showed the divergent behavior of middle ear epithelium compared with the cytokeratin expression of the other two types of epithelium. Middle ear epithelium was characterized by the presence of cytokeratins 4, 8, 18, and 19, whereas in both cholesteatoma and meatal epidermis cytokeratin 10 predominated. Furthermore, cholesteatoma showed an infrequent focal presence of cytokeratins 4, 18, and 19. The similarity between cholesteatoma and meatal epidermis with respect to morphology, and the presence of cytokeratin 10 support an epidermal origin of cholesteatoma. However, a metaplastic origin cannot be excluded, because of the infrequent occurrence of a small amount of cytokeratins 4, 18, and 19 in cholesteatoma matrix that was not found in meatal epidermis but was a component of the cytokeratin pattern of middle ear epithelium.

Distribution of HLA class II molecules in epidermal Langerhans cells in situ.

We performed immunoelectron microscopic studies to investigate the expression of HLA class II molecules in Langerhans cells (LC). In the epidermis, LC expressed class II molecules on the plasma membrane of the dendrites, resulting in a class II positive reticulo-epithelial network, but not on the surface of the cell body. In contrast, isolated LC as well as activated LC in situ displayed an even and strong expression of class II molecules on their entire cell surface. Therefore, isolation and/or activation results in redistribution and up-regulation of class II molecules on the cell surface. In addition, double-labeling experiments were carried out with monoclonal antibodies to class II antigens and to LAMP-1, CD63 and alpha-glucosidase, specific markers for organelles of the endosomal/lysosomal system. The results show expression of class II molecules on intracellular, electron-dense vesicular structures, and co-localization of class II molecules and the markers for late endosomes and early lysosomes in human LC in situ. Expression of these markers was not found on Birbeck granules, an LC-specific organelle.