HSV-1-infected oral epithelial cells are targets for natural killer cells

A mechanism of cell-mediated immunity was investigated to determine whether natural killer (NK) cells were able to lyse antigenically-altered epithelial cell targets. Using standard four-hour chromium-release assays, we tested human peripheral blood lymphocytes against autologous untreated epithelial cells and autologous HSV-1-infected epithelial cells and calculated the percentage of lysis. With adherent cell-depleted peripheral blood, only epithelial cells infected with virus were lysed (p = 0.009). Evidence that NK cells were responsible for the lysis exists because: (1) peripheral blood lymphocytes were able to lyse allogeneic as well as autologous virus-infected cells; (2) when NK cells were depleted with the lysosomotropic drug L-leucine methyl ester, cytotoxicity against infected targets was abrogated; and (3) depletion of NK cells by the monoclonal antibody Leu-11b, plus complement, also eliminated cytotoxicity against virus-infected targets. Additional evidence suggests that lysis of targets does not involve antibody-dependent cellular cytotoxicity. These findings indicate that NK cells have the potential to perform a similar in vivo immunologic role in the oral cavity and initiate cell-mediated lysis of virus-infected epithelial cells.