title: Partial activation of CD8+ T cells by a self-derived peptide.
abstract: T cells are normally activated when the peptide for which they are specific is presented to them in the context of the appropriate major histocompatibility complex (MHC) (class I and Class II for CD8+ and CD4+ T cells, respectively). An increasing body of evidence indicates that structural homologues of the immunogenic peptide can partially activate or antagonize CD4+ T cells. CD8+ T cells may also be partially antagonized by such peptides, and self-derived peptides of this type may play a role in CD8+ T cell selection in the thymus. Activated CD8+ T cells lyse their targets by perforin-dependent granule exocytosis and by inducing apoptosis mediated by CD95 (also known as Fas or APO1) with its ligand (CD95L). Here we show that a clone of Kd-restricted CD8+ T cells specific for influenza haemagglutinin, which can also be activated in a crossreactive manner by a peptide derived from a myeloma tumour immunoglobulin heavy-chain variable region (IgVH) to kill by both routes, kills only by the CD95-CD95L pathway when stimulated by the corresponding germline IgVH peptide. As this germline IgVH peptide differs from the tumour peptide only at a single position buried in the MHC-binding groove, this indicates that CD95-CD95L-mediated killing can be triggered independently of the perforin-mediated pathway, and can be selectively affected by changes in MHC conformation.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D016923:Cell Death; D002460:Cell Line; D002999:Clone Cells; D004247:DNA; D006183:H-2 Antigens / Q000276:immunology; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology*; D017493:Leukocyte Common Antigens / Q000276:immunology; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D009194:Myeloma Proteins / Q000235:genetics / Q000276:immunology*; D010446:Peptide Fragments / Q000276:immunology*; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D015398:Signal Transduction
chemical_list: D006183:H-2 Antigens; C024755:H-2K(K) antigen; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral; D007143:Immunoglobulin Heavy Chains; D008562:Membrane Glycoproteins; D009194:Myeloma Proteins; D010446:Peptide Fragments; D052899:Pore Forming Cytotoxic Proteins; D011948:Receptors, Antigen, T-Cell; D054353:Perforin; D004247:DNA; D017493:Leukocyte Common Antigens