Tonsillar epithelial dendritic cells. Demonstration by lectin binding, immunohistochemical characterization, and ultrastructure

The association of tonsillar epithelium with lymphoid tissue suggests a functional relationship in the generation of local immune responses analogous to skin. Therefore, we investigated this epithelium for the presence of dendritic cells similar to epidermal Langerhans cells. Clusters of tonsillar epithelial dendritic cells (TEDC) were revealed by binding of the lectin peanut agglutinin, a feature not previously directly demonstrated for this cell type. Similar to epidermal Langerhans cells, TEDC showed immunoreactivity for antibodies to S-100, T6, and Ia antigens. Ultrastructurally, TEDC had features most similar to epidermal indeterminate cells. In addition, the tonsillar epithelium showed regional variation in the types of intraepithelial lymphocytes present. Surface epithelium contained T cells predominantly of helper/inducer phenotype, while the crypt epithelium contained a mixture of B cells, plasma cells, and T cells of both helper/inducer and suppressor cytotoxic phenotypes. These findings, together with the demonstration of TEDC, suggest that the tonsillar epithelial microenvironment, like skin, provides a site of cell-cell interactions important in initiating immune responses.