INDUCTION OF LYMPHOCYTES CYTOTOXIC TO ORAL EPITHELIAL-CELLS BY STREPTOCOCCUS-MITIS SUPERANTIGEN

The preparation of a superantigenic fraction F-2 from the culture supe rnatant of Streptococcus mitis 108, a fresh isolate from human tooth s urfaces, was reported previously. Now, to determine the possible patho genic role of the superantigen in oral mucosal diseases, we examined t he cytotoxic effects of human peripheral blood T-cells activated with F-2 on human oral epithelial cells. T-cells activated with F-2 were cy totoxic to the human squamous carcinoma HO-1-N-1 cells derived from th e oral mucosa, similar to those activated with Staphylococcus aureus e nterotoxin B (SEB). This cytotoxic effect was increased in a dose-depe ndent manner by the addition of the respective stimulant, F-2 or SEB, to the cytotoxic assay system. F-2 endowed mainly CD8(+) T-cells with cytotoxic activity. Pretreatment with human interferon gamma increased the sensitivity of the HO-1-N-1 cells to the cytotoxic effects of F-2 -activated T-cells. The F-2-activated T-cells were also cytotoxic to h uman keratinocytes derived from gingiva. There was no correlation betw een the degree of cytotoxicity and the levels of tumor necrosis factor alpha in co-cultures of F-2-activated T-cells and HO-1-N-1 cells. A d ouble-chamber plate experiment revealed no cytotoxic effects when the F-2-activated T-cells were separated from the HO-1-N-1 cells. Supernat ants of the co-cultures of target and effector cells were not cytotoxi c to HO-1-N-1 cells. These findings suggest that the cytotoxic effects of the F-2-activated T-cells on HO-1-N-1 cells were mediated not by s oluble factors but by the direct interaction between the activated T-c ells and the target cells. The cytotoxicity of the F-2-activated T-cel ls against HO-1-N-1 cells was markedly inhibited by monoclonal antibod ies (MAbs) against CD11a and CD54, but was only slightly inhibited by MAbs against human leukocyte antigen (HLA)-DR and CD2. Thus, the inter action between lymphocyte-function-associated antigen-1 (LFA-1) and in tercellular adhesion molecule-1 (ICAM-1) was crucial for the F-2-depen dent T-cell-mediated cytotoxicity against oral epithelial cells, while HLA-DR and CD2 molecules are not necessarily involved in the cytotoxi city observed.