Class II antigen expressing cells in experimentally induced pulpitis.

This study reports on the occurrence of class II antigen expressing cells in inflammatory lesions experimentally induced in the rat incisor pulp. Concanavalin A and lipopolysaccharide of Bacteroides gingivalis were applied to the exposed pulp following a preparation through alveolar bone and dental tissues in the midpart of the root. In a set of control teeth, pulpal exposures were capped with Cavit without the placement of antigenic material. Animals were killed after 3, 12, 24, 48 or 96 hours. Pulp tissue specimens were subjected to immunohistochemical analysis utilizing a monoclonal mouse anti-rat class II antigen antibody. Semi-quantitative assessment of positively stained cells was carried out under the light microscope. Significantly more class II antigen expressing cells were identified in the challenged pulps than in the controls at all experimental periods. The increase in cells peaked at 48 hours to taper off at the subsequent 96-hour observation. The rapid and intense influx of class II antigen expressing cells suggests that these cells are associated with the initial defence of the dental pulp.