title: IL-2 induces Fas ligand/Fas (CD95L/CD95) cytotoxicity in CD8+ and CD4+ T lymphocyte clones.
abstract: IL-2 is a T cell growth factor that has pleiotropic functions in T cell differentiation, induction of lymphokine-activated killer cells, and regulation of immune responses. In studying TCR triggering of perforin or Fas ligand (FasL)/Fas (CD95 ligand/CD95) cytotoxicity in our influenza-specific T cell clones, we found that IL-2 can also induce FasL/Fas cytotoxicity. IL-2 induces FasL/Fas cytotoxicity in our CD8+ and CD4+ Th1 clones, but not in our CD4+ Th2 clones. IL-2 induction of cytolytic activity occurs when the CD8+ T cells are refractory to IL-2-induced proliferation. This killing is Ag independent, MHC unrestricted, and blocked by Fas.Fc fusion protein. IL-2 induces FasL/Fas cytotoxicity in a dose-dependent manner, but does not induce high levels of FasL expression as detected by flow cytometry. TCR triggered FasL/Fas cytotoxicity is detectable in CD8+ and Th1 clones by 3 h and peaks at 6 h; high levels of killing are maintained for at least 24 h. Similarly, IL-2 induces FasL/Fas killing in CD8+ and Th1 clones within 3 h of stimulation and maintains high levels for at least 24 h. TCR-triggered FasL/Fas killing is inhibited by emetine and cyclosporin A, whereas IL-2-induced FasL/Fas killing is inhibited by emetine, but not by cyclosporin A. These results demonstrate a second mechanism to induce FasL/Fas cytotoxicity in CD8+ and Th1 clones and may explain IL-2 induction of Ag-independent MHC-unrestricted lymphokine-activated killer cell activity.
authors.affiliation: Department of Microbiology and the Beirne B. Carter Center for Immunology Research, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Esser
authors.forename: R D
authors.initials: RD
authors.lastname: Dinglasan
authors.forename: B
authors.initials: B
authors.lastname: Krishnamurthy
authors.forename: C A
authors.initials: CA
authors.lastname: Gullo
authors.forename: M B
authors.initials: MB
authors.lastname: Graham
authors.forename: V L
authors.initials: VL
authors.lastname: Braciale
mesh_terms: D000954:Antigens, Surface / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002999:Clone Cells; D016572:Cyclosporine / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic; D004640:Emetine / Q000494:pharmacology; D053222:Fas Ligand Protein; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007376:Interleukin-2 / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology; D019014:fas Receptor / Q000276:immunology*
chemical_list: D000954:Antigens, Surface; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D008562:Membrane Glycoproteins; D011948:Receptors, Antigen, T-Cell; D019014:fas Receptor; D016572:Cyclosporine; D004640:Emetine