LOCAL IMMUNE-RESPONSE IN THE SKIN OF THE EXTERNAL AUDITORY MEATUS - AN IMMUNOHISTOCHEMICAL STUDY

Cerumen plays an important role in the protection of the external audi tory meatus against several kinds of damage. Its hydrophobic propertie s, due to the high concentration of lipids, shelter the canal from phy sical damages, while other components probably protect against certain microbial strains. Nevertheless there has been considerable dispute i n the literature with regard to the antibacterial activity of cerumen. Because of the importance of the role of immunoglobulins (Ig) in loca l defense mechanisms, we attempted to study, by immunohistochemical me thods, the presence and localization of the cells necessary to activat e an Ig-mediated immune response and the epithelial expression of immu noglobulin A (IgA), immunoglobulin M (IgM), and immunoglobulin G (IgG) in order to obtain information about a local immune response in those areas of the skin that take part in cerumen production. Our findings indicate that in the human skin of the external auditory canal the cel ls necessary to activate an antibody-mediated immune response were loc alized in the different layers of the epidermis and/or in the dermis s urrounding the sebaceous and ceruminous glands and the piliary follicl e, while an intense immunoreactivity for IgA and IgG was observed in t he epithelial layers of the skin. The results suggest that the externa l auditory canal is protected from the insults of pathogens by an anti body-mediated local immune response, because all the effector componen ts of an active local immune system are present. (C) 1997 Wiley-Liss, Inc.