Staphylococcal enterotoxins direct and trigger CTL killing of autologous HLA-DR+ mononuclear leukocytes and freshly prepared leukemia cells

Attempts have been made to induce cytolytic T cells to kill target cells that do not express the appropriate target molecules by crosslinking the T cells and the target cells in various ways. One successful strategy has been to use heteroconjugates or bispecific monoclonal antibodies reacting with T cell molecules with activating properties (e.g., mab directed to CD3/TCR) and target cell surface antigens. In this report we show that Staphylococcal enterotoxins (SE) direct human T lymphocytes to execute cytotoxicity toward MHC class II-expressing Raji cells, but not against MHC class II-deficient Raji mutant RJ 2.2.5. Both HLA-DR+ and HLA-DR- effector T lymphocytes are effective in the killing of Raji cells coated with SE. The Staphylococcal enterotoxin-dependent cell-mediated cytotoxicity (SDCC) is a rapid T lymphocyte-mediated cytolytic mechanism killing the targets within an hour of incubation. HLA-DR+ target cells are sensitized to be killed within minutes of incubation with picomolar concentrations of SE. SE-sensitized Raji cells remain targets for SDCC after overnight culture at 37 degrees C, demonstrating that the sensitive state is relatively stable. SEA- and SEB-selective cytolytic T cell lines were established to illustrate the clonal variability of SDCC effectors with respect to SE specificity. We also demonstrate that autologous monocytes and activated T lymphocytes as well as B lymphocytes and freshly prepared HLA-DR+ leukemic cells are excellent targets in SDCC.