[Immunohistochemical identification of cholesteatoma-associated macrophage populations]

Extensive bone resorption occurring in aural cholesteatoma is responsible for the severe complications of this disease. In the area of active bone destruction, typical multinucleated osteoclasts are rarely seen, but a heavy cellular infiltrate is found. In the present study we tried to characterize the immunophenotype and the functional state of the cells infiltrating the stroma and the epithelial layer of aural cholesteatoma, using a panel of monoclonal antibodies directed against cell type specific antigens. The results were compared with normal retroauricular skin. The vast majority of cells infiltrating the stroma was bone marrow derived and consisted of T-cells and macrophages. By means of the activation markers HLA-DR and Interleukin-2 receptor an immunologically activated state of the majority of infiltrating cells in cholesteatomas was shown. The great number of activated macrophages in cholesteatomas seems to be very important in the cholesteatomatous immunological process. Because of their various immunological functions (antigen presentation to T-lymphocytes, participation in ingestion and killing of different invading microorganisms and synthesizing a great number of substances involved in host defence and inflammation) these cells play a central role in human immunological system. Langerhans cells, however, did not appear to be involved in the immune process of cholesteatoma. The characteristics of the infiltrating cell population with the great number of phagocytic cells suggest an active immune process resulting in autoaggressive bone resorption.