title: Two distinct mechanisms of cytotoxicity mediated by herpes simplex virus-specific CD4+ human cytotoxic T cell clones.
abstract: The present study was undertaken to elucidate the mechanisms responsible for the cytotoxicity of herpes simplex virus (HSV)-specific CD4+ human cytotoxic T lymphocyte (CTL) clones, focusing on perforin and membrane-bound lymphotoxin (LT) (tumor necrosis factor-beta). Two HSV-specific CD4+ CTL clones, which expressed both perforin and membrane-bound LT, exerted HSV-specific cytotoxicity and cytotoxicity against LT-sensitive L929 cells. These CD4+ CTL clones lysed HSV-infected cells directly in an HLA class II-restricted manner and did not exhibit "bystander killing." The culture supernatants of these clones stimulated with HSV antigen showed no cytotoxicity against HSV-infected cells or L929 cells, suggesting that adhesion to target cells is essential to their antigen-specific and antigen-nonspecific cytotoxicities. The cytotoxicities of these clones against HSV-infected autologous cells were inhibited by an anti-CD3 monoclonal antibody but not by an anti-LT antibody. Conversely, their cytotoxicities against L929 cells appeared to be partially inhibited by the anti-LT antibody but not by the anti-CD3 monoclonal antibody. Furthermore, target cell DNA fragmentation induced by these CD4+ CTL clones was apparently observed in L929 cells but only faintly detected in HSV-infected autologous cells. L929 cell DNA fragmentation was also inhibited by adding the anti-LT antibody to CD4+ CTL cultures. These data suggest that some CD4+ CTL possess at least two cytolytic mediators, i.e., perforin and membrane-bound LT simultaneously, and can exert both antigen-specific cytotoxicity via two distinct mechanisms, necrosis and apoptosis.
authors.affiliation: First Department of Internal Medicine, Ehime University School of Medicine, Shigenobu, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yasukawa
authors.forename: Y
authors.initials: Y
authors.lastname: Yakushijin
authors.forename: S
authors.initials: S
authors.lastname: Fujita
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000956:Antigens, Viral / Q000276:immunology; D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology*; D002999:Clone Cells; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic / Q000235:genetics; D004249:DNA Damage / Q000276:immunology; D006801:Humans; D008213:Lymphocyte Activation; D008233:Lymphotoxin-alpha / Q000096:biosynthesis / Q000276:immunology; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D018139:Simplexvirus / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000956:Antigens, Viral; D017252:CD3 Complex; D015704:CD4 Antigens; D008233:Lymphotoxin-alpha; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin