The ultrastructure of initial changes in hapten-exposed rat oral mucosa

The experimentally induced cell-mediated immune reaction has been examined ultrastructurally in rat oral mucosa, using DNCB/DNFB as haptens. In skin-presensitized animals, an increased number of mononuclear cells was found in the epithelium at a very early phase (15-60 min) after hapten exposure. In nonsensitized animals, an increased number of cells was evident in hapten-exposed tissue also very early in the reaction. Mononuclear cells appeared in the connective tissue but very few in the epithelium. Interaction between mononuclear cells and Langerhans cells could be demonstrated in both experimental groups.