Epithelial dendritic cells in pathological human oral tissues.

Epithelial dendritic cells (EDC) were examined in human oral tissues with non-specific keratosis, lichen planus and squamous cell carcinoma. Acetone-fixed frozen sections were stained using an indirect immunoperoxidase technique and monoclonal antibodies to the human CD1 thymocyte (OKT6) and HLA-DR antigens. Significantly more T6+ and DR+ EDC were present in lichen planus tissues than normal controls, tissues with non-specific keratosis and the epithelial overlying/adjacent to squamous cell carcinomas, the latter tissues having comparable numbers of both T6+ and DR+ EDC. By contrast, significantly fewer T6+ EDC and significantly more DR+ cells were present in the invasive epithelium of squamous cell carcinomas than the overlying/adjacent epithelium of carcinomas, the non-specific keratosis group and the normal tissues. 23-60% of pathological tissues had either focal or general DR+ reactivity in keratinocytes, but there was no correlation between the density of T6+ or DR+ EDC and the keratinocyte DR status of the tissues. The results suggest that immunological enhancement occurs in lichen planus and possibly immunological impairment may characterize invasive squamous cell carcinoma.