title: Peptide modification or blocking of CD8, resulting in weak TCR signaling, can activate CTL for Fas- but not perforin-dependent cytotoxicity or cytokine production.
abstract: This study describes a form of partial agonism for a CD8+ CTL clone, S15, in which perforin-dependent killing and IFN-gamma production were lost but Fas (APO1 or CD95)-dependent cytotoxicity preserved. Cloned S15 CTL are H-2Kd restricted and specific for a photoreactive derivative of the Plasmodium berghei circumsporozoite peptide PbCS 252-260 (SYIPSAEKI). The presence of a photoactivatable group in the epitope permitted assessment of TCR-ligand binding by TCR photoaffinity labeling. Selective activation of Fas-dependent killing was observed for a peptide-derivative variant containing a modified photoreactive group. A similar functional response was obtained after binding of the wild-type peptide derivative upon blocking of CD8 participation in TCR-ligand binding. The epitope modification or blocking of CD8 resulted in an > or = 8-fold decrease in TCR-ligand binding. In both cases, phosphorylation of zeta-chain and ZAP-70, as well as calcium mobilization were reduced close to background levels, indicating that activation of Fas-dependent cytotoxicity required weaker TCR signaling than activation of perforin-dependent killing or IFN-gamma production. Consistent with this, we observed that depletion of the protein tyrosine kinase p56(lck) by preincubation of S15 CTL with herbimycin A severely impaired perforin- but not Fas-dependent cytotoxicity. Together with the observation that S15 CTL constitutively express Fas ligand, these results indicate that TCR signaling too weak to elicit perforin-dependent cytotoxicity or cytokine production can induce Fas-dependent cytotoxicity, possibly by translocation of preformed Fas ligand to the cell surface.
authors.affiliation: Ludwig Institute for Cancer Research, Lausanne Branch, Epalinges, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Kessler
authors.forename: D
authors.initials: D
authors.lastname: Hudrisier
authors.forename: M
authors.initials: M
authors.lastname: Schroeter
authors.forename: J
authors.initials: J
authors.lastname: Tschopp
authors.forename: J C
authors.initials: JC
authors.lastname: Cerottini
authors.forename: I F
authors.initials: IF
authors.lastname: Luescher
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001386:Azides; D016227:Benzoquinones; D016827:CD8 Antigens / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling; D002999:Clone Cells; D003602:Cytotoxicity, Immunologic; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000939:Epitopes / Q000737:chemistry / Q000187:drug effects / Q000276:immunology; D053222:Fas Ligand Protein; D006183:H-2 Antigens / Q000276:immunology; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D047029:Lactams, Macrocyclic; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000037:antagonists & inhibitors / Q000502:physiology; D012515:Mast-Cell Sarcoma / Q000473:pathology; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology*; D054353:Perforin; D010766:Phosphorylation / Q000187:drug effects; D019920:Photoaffinity Labels; D010962:Plasmodium berghei / Q000276:immunology; D052899:Pore Forming Cytotoxic Proteins; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000276:immunology*; D011809:Quinones / Q000494:pharmacology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D017828:Rifabutin / Q000031:analogs & derivatives; D012459:Salicylates; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase; D019014:fas Receptor / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D001386:Azides; D016227:Benzoquinones; D016827:CD8 Antigens; D004791:Enzyme Inhibitors; D000939:Epitopes; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D006183:H-2 Antigens; C024755:H-2K(K) antigen; D007140:Immunoglobulin Fab Fragments; D047029:Lactams, Macrocyclic; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D019920:Photoaffinity Labels; D052899:Pore Forming Cytotoxic Proteins; D015800:Protozoan Proteins; D011809:Quinones; D011948:Receptors, Antigen, T-Cell; D012459:Salicylates; C105341:Ser-Tyr-Ile-Pro-Ser-Ala-Glu-Lys-Ile protein, Plasmodium; C054979:antigen T cell receptor, zeta chain; D019014:fas Receptor; D054353:Perforin; D017828:Rifabutin; C063873:4-azidosalicylic acid; C020754:herbimycin; D007371:Interferon-gamma; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase; C497262:Zap70 protein, mouse