Enzyme histochemical characterization of mononuclear cells in human dental periapical chronic inflammatory lesions

Cell infiltrates in sections of paraffin-embedded tissue of 36 human periapical inflammatory lesions (15 granulomas and 21 cysts) were examined by staining for acid alpha-naphthyl acetate esterase (ANAE). Thirty-four of the lesions showed ANAE reactive T lymphocytes, plasma cells and cells of the monocyte/macrophage cell line. Large granular lymphocytes (NK cells) could not be identified with certainty among the ANAE positive cells. Two specimens were free of ANAE reactive cells. Differential cell counts on sections from 15 lesions (7 granulomas and 8 cysts) showed that T lymphocytes were the predominating ANAE reactive cells (23%), followed by plasma cells (15%) and monocytes/macrophages (11%). 51% of the inflammatory cells were ANAE negative. There was no marked difference between the granulomas and the cysts. Inhibition with NaF (10-100 mM) gave a gradual reduction in number of ANAE positive cells, some macrophages being the only cells resistant to 100 mM NaF. The results suggest that both humoral and cellular immune reactions are likely to occur in periapical inflammatory lesions.