Characterization of mononuclear cells in the human oral mucosa

A histochemical investigation of 16 sites of post-mortem oral mucosa was carried out in an attempt to define any organized lymphoid tissue in the mouth. Whereas lymphoid tissue was found, as expected, in the palatine and lingual tonsils, only 1 out of 240 specimens revealed lymphoid aggregations at other mucosal sites. However, mononuclear cells were scattered in the lamina propria of the oral mucosa and this varied from 53 cells/mm2 in the fetus to 83 cells/mm2 in old age. Non-keratinized oral mucosa showed a significantly higher number of mononuclear cells than keratinized mucosa. Up to 53 per cent of the cells stained with acid alpha naphthyl acetate esterase (ANAE), consistent with T cells, and up to 25 per cent gave a staining reaction consistent with monocytes. Some of the ANAE-negative cells were B lymphocytes. The presence of T cells was also examined by using the acid phosphatase reaction. It is suggested that, with the exception of the palatine and lingual tonsils, organized lymphoid tissue is not normally found in the rest of the mouth. However, the presence of scattered mononuclear cells at all ages and in all the sites of the oral mucosa examined suggests that these cells may provide a local surveillance mechanism.