Ia+ epithelial dendritic cells during oral carcinogenesis in the rat

Epithelial dendritic cells (EDC) were examined during the induction and growth of oral squamous cell carcinomas in rats treated with the carcinogen 4-Nitroquinoline N-oxide (4NQO). Acetone-fixed frozen sections of the palate and tongue were stained using an indirect immunoperoxidase technique and a monoclonal antibody to rat Ia (MRC OX-6). After 6 months there was a significant increase in Ia+ EDC/mm2 in non-invasive palatal and lingual epithelium compared with untreated and solvent painted controls. Furthermore, after 9 months there were significantly more Ia+ EDC/mm2 in non-invasive lingual epithelium compared with invasive epithelium or the epithelium overlying/adjacent to squamous cell carcinomas of the tongue. Although there were no significant differences of Ia+ EDC/mm2 between infiltrating epithelium of lingual carcinomas and non-invasive epithelium overlying/adjacent to the tumour, these tissues did contain significantly more Ia+ EDC than lingual epithelium from either solvent-only or untreated controls. The results indicate that treatment with 4NQO stimulates an increase in Ia+ EDC numbers which, although remaining higher than in controls, is not maintained within, or adjacent to, sites of neoplastic change.