Lytic effects of serum and mononuclear leukocytes on oral epithelial cells in recurrent aphthous stomatitis

A radioisotope-release assay, utilizing 51Cr-labeled epithelial cells derived from non-keratinizing oral mucosa, was developed to investigate in vitro cytolytic reactions correlating with recurrent aphthous stomatitis (RAS). The cytolytic effects of sera and mononuclear leukocytes from patients in the early stage of ulceration were compared with those from matched RAS-negative control subjects. RAS sera induced significantly more cytolysis than did matched control sera. Heating the RAS or control sera for 30 min at 56 degrees C abrogated their cytotoxic activity. RAS mononuclear leukocytes, like their matched controls, showed no significant direct cytotoxicity. Heat-inactivated RAS or control sera acting in concert with RAS or control mononuclear leukocytes showed no consistent cytolytic effects. However, the heat-inactivated sera of some RAS patients, when combined with autologous mononuclear leukocytes, induced significantly more cytolysis than did either component acting alone. Thus heat-labile humoral factors and, in some cases, mononuclear leukocytes acting in concert with heat-stable serum factors are implicated in RAS-associated in vitro cytolytic reactions. These findings suggest that the effector mechanisms of such reactions include both complement-mediated and antibody-dependent cell-mediated cytotoxicity.