Langerhans cells have been found in cholesteatomas for many years. It is believed that they are immunocompetent cells and have the same role in cell-mediated immunologic mechanisms in cholesteatoma as well as in skin. This study used the transmission electron microscope to observe the cellular characteristics of Langerhans cells and the apposition phenomenon of Langerhans cells with lymphocyte-like cells in human middle ear cholesteatomatous tissue. These findings are evidence for cell-mediated immune responses in middle ear cholesteatomas. In vitro Langerhans cells conditioned medium prepared from Lewis rat skin was used to show its effects on protein synthesis and the differentiation of basal cells. Since the cellular behaviour of basal cells is important in the development and pathogenesis of cholesteatoma, the present study shows that Langerhans cells may have some role in the clinical formation of a cholesteatoma. Since cells extracted from rat skin may have a different response from that of cells from human middle ear cholesteatoma, further investigations are necessary to compare the biological effects of both tissues.
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