In situ characterization of mononuclear cells in human dental periapical inflammatory lesions using monoclonal antibodies.

Mononuclear cells in cryostat sections of human dental periapical inflammatory lesions were studied with the aid of murine monoclonal antibodies and with indirect immunofluorescence microscopy. T lymphocytes (OKT3-positive cells) made up a major part of the cells in the infiltrates. They were found mainly in clusters, although single cells were also seen. T helper cells (OKT4) were more numerous than suppressor/cytotoxic T cells (OKT8-positive cells), with a ratio of approximately 2:1. Langerhans cells (OKT6-positive cells) were not demonstrated: only a few scattered HNK 1-positive cells, probably natural killer cells, were detected. A large number of OKM1- and OKIa 1-positive cells were detected in the infiltrates. Their size and number varied considerably in the different areas of the sections. These cells are probably macrophages. Sheets of small OKIa 1-positive cells were also demonstrated, indicating the presence of B lymphocytes or activated T lymphocytes. The results indicate that immune reactions may be of importance in the pathogenesis of periapical inflammatory lesions.