Normal distribution of lysozyme- and lactoferrin-secreting cells in the chinchilla tubotympanum.

The distribution of the antibacterial enzyme lysozyme- and lactoferrin-secreting cells in the tubotympanum of normal chinchillas was studied using an immunohistochemical technique. The middle ear mucosa contained lysozyme-secreting cells and lactoferrin-secreting cells. The former were localized primarily in the columnar epithelium area and the latter primarily in the cuboidal epithelium area (that contains serous cells) of the transitional zone. In the eustachian tube, the lysozyme was localized in goblet cells of the mucosal epithelium and mucous cells of the glands, while lactoferrin was localized in serous cells of the glands. Our results indicate that secretory lysozyme and lactoferrin are secreted by different cell types (mucous or serous), supporting the notion of heterogeneity of the secretory cells of the tubotympanum. This finding is consistent with the concept that antibacterial enzyme secretion is an integral part of the normal mucosal defense system in the tubotympanum.