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102
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Alam SM, Travers PJ, Wung JL, Nasholds W, Redpath S, Jameson SC, Gascoigne NR. T-cell-receptor affinity and thymocyte positive selection. Nature 1996; 381:616-20. [PMID: 8637599 DOI: 10.1038/381616a0] [Citation(s) in RCA: 513] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Development of thymocytes involves two distinct outcomes resulting from superficially similar events. Recognition by thymocytes of major histocompatibility complex (MHC) proteins plus peptides leads to their rescue from apoptosis (positive selection), and recognition of antigenic peptide induces cell death (negative selection). Antigen analogues, and sometimes low concentrations of antigenic peptide, induce positive selection; such analogues are often antagonists of mature T-cell clones. Various models seek to explain how recognition of different peptide/MHC complexes leads to such different outcomes: quantitative models relate response to the affinity, avidity or kinetics of T-cell-antigen receptor (TCR) binding, whereas qualitative models require conformational or spatial changes in the TCR or associated molecules to modulate signal transduction. We have used surface plasmon resonance to measure the kinetics of TCR interactions with positively and negatively selecting ligands to distinguish between these models, and find that affinity correlates to the outcome of selection. A 'window' of affinity resulting in positive selection extends over a 1-log range starting threefold below the affinity for negative selection.
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Affiliation(s)
- S M Alam
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA
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103
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Abstract
T cell receptors (TCR) have a low affinity for the MHC and the presented peptides (MHCpep). The low affinity of the TCR is crucial in T cell recognition and activation. Nevertheless, I propose that the TCR is perfectly capable of specifically binding MHCpep with high affinity. This hypothesis is supported by several data. Among them, the frequency of negatively selected immature T cells and of high affinity alloreactive T cells. Structural and functional analysis indicates that the TCR binding regions are quite similar to those of immunoglobulins. This implies similar binding strategies and suggests that there are no structural constraints on TCR affinity. The possible existence of high affinity TCR is relevant for current views on immune recognition, alloreactivity and peptide antagonism. In particular, it supports a model of immune recognition as unselected higher affinity binding to newly encountered peptides. The actual production of specific affinity TCR may also prove crucial for a soluble T cell receptor-based immunotherapy and for the co-crystallization of TCR with MHC and peptides.
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Affiliation(s)
- S Alberti
- Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
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104
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Abstract
The key to understanding afferent immunity is the mechanism of activation of T lymphocytes by specialized antigen presenting cells, which bind antigenic peptide to Class II major histocompatibility molecules, and stimulate T cells via Signal 1 (antigen) and Signal 2 (costimulation). The best studied costimulatory pathway is the interaction of B7-1 or B7-2 ligand molecules on antigen presenting cells with CD28 or CTLA-4 receptors on T cells. T cell signaling occurs through the T cell receptor-CD3 complex and is augmented by cosignaling via CD4, CD8, and CD45. The activation of T cells to alloantigen occurs by either a direct pathway of recognition of allogenic major histocompatibility molecules (with or without an associated endogenous peptide), or by an indirect pathway of recognition of processed donor alloantigens via recipient antigen presenting cells. Afferent immunity on the musculoskeletal system is of special interest because of the absence of viable donor antigen presenting cells in processed grafts that makes them susceptible to the indirect pathway of alloantigen recognition.
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Affiliation(s)
- A A Czitrom
- University of Texas, Southwestern Medical Center, Medical City Dallas Hospital, Advanced Surgical Institutes, USA
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105
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Abstract
alpha beta T cells specifically recognize a ligand composed of a peptide bound to a self-major-histocompatibility-complex molecule, but the recognition of slightly altered ligands by T cells can lead to a partial activation. This flexibility is crucial for T-cell development and can have both beneficial and harmful effects on peripheral T cells.
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Affiliation(s)
- G J Kersh
- Center for Immunology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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106
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Davis SJ, van der Merwe PA. The structure and ligand interactions of CD2: implications for T-cell function. IMMUNOLOGY TODAY 1996; 17:177-87. [PMID: 8871350 DOI: 10.1016/0167-5699(96)80617-7] [Citation(s) in RCA: 298] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- S J Davis
- Molecular Sciences Division, Nuffield Dept. of Clinical Medicine, University of Oxford, UK.
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107
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Abstract
Recent crystallographic studies of T cell antigen receptor (TCR) fragments from the alpha and beta chains have now confirmed the expected structural similarity to corresponding immunoglobulin domains. Although the three-dimensional structure of a complete TCR alpha beta heterodimer has not yet been determined, these results support the view that the extracellular region should resemble an immunoglobulin Fab fragment with the antigen-binding site formed from peptide loops homologous to immunoglobulin complementarity-determining regions (CDR). These preliminary results suggest that CDR1 and CDR2 may be less variable in structure than their immunoglobulin counterparts, consistent with the idea that they may interact preferentially with the less polymorphic regions of the molecules of the major histocompatibility complex. The region on the variable beta domain responsible for superantigen recognition is analyzed in detail. The implications for T cell activation from the interactions observed between domains of the alpha and beta chains are also discussed in terms of possible dimerization and allosteric mechanisms.
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Affiliation(s)
- G A Bentley
- Unité d'Immunologie Structurale, Institut Pasteur, Paris, France
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108
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Sebzda E, Kündig TM, Thomson CT, Aoki K, Mak SY, Mayer JP, Zamborelli T, Nathenson SG, Ohashi PS. Mature T cell reactivity altered by peptide agonist that induces positive selection. J Exp Med 1996; 183:1093-104. [PMID: 8642251 PMCID: PMC2192317 DOI: 10.1084/jem.183.3.1093] [Citation(s) in RCA: 129] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Recent studies have investigated how defined peptides influence T cell development. Using a T cell receptor-transgenic beta2-microglobulin-deficient model, we have examined T cell maturation in fetal thymic organ cultures in the presence of various peptides containing single-alanine substitutions of the strong peptide agonist, p33. Cocultivation with the peptide A4Y, which contains an altered T cell contact residue, resulted in efficient positive selection. Several in vitro assays demonstrated that A4Y was a moderate agonist relative to p33. Although A4Y promoted positive selection over a wide concentration range, high doses of this peptide could not induce clonal deletion. Thymocytes maturing in the presence of A4Y were no longer able to respond to A4Y, but could proliferate against p33. These studies demonstrate that (a) peptides that induce efficient positive selection at high concentrations are not exclusively antagonists; (b) some agonists do not promote clonal deletion; (c) positive selection requires a unique T cell receptor-peptide-major histocompatibility complex interaction; and (d) interactions with selecting peptides during T cell ontogeny may define the functional reactivity of mature T cells.
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Affiliation(s)
- E Sebzda
- Ontario Cancer Institute, Department of Medical Biophysics, Toronto, Canada
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109
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Williams O, Tanaka Y, Bix M, Murdjeva M, Littman DR, Kioussis D. Inhibition of thymocyte negative selection by T cell receptor antagonist peptides. Eur J Immunol 1996; 26:532-8. [PMID: 8605917 DOI: 10.1002/eji.1830260305] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The T cell receptor (TCR) recognizes antigenic peptide presented by major histocompatibility complex (MHC) molecules. Analogs of antigenic peptides have been shown to inhibit antigen-specific T cell responses, a phenomenon described as TCR antagonism. We have examined the effect of a natural variant of an antigenic peptide and a synthetic peptide analog, on the responses of mature T cells and immature thymocytes from an alpha-beta TCR-transgenic mouse (F5), the TCR of which recognizes a nonamer peptide from the nucleoprotein (NP) of influenza virus in the context of the H-2Db MHC molecule. Both peptides were shown to antagonize specifically the T cells cytolytic response without being able directly to stimulate mature T cells from these transgenic mice. Furthermore, a negative selection assay in vitro was used to demonstrate for the first time that antagonistic peptides are capable of antagonizing thymocyte deletion induced by antigenic peptides. These data suggest that the final selection of a T cell could be the result of a balance between the positive and negative influences of endogenous peptide ligands.
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MESH Headings
- Amino Acid Sequence
- Animals
- Cell Differentiation/immunology
- Cell Line
- Cytotoxicity, Immunologic
- Influenza A virus/immunology
- Lymphocyte Activation/drug effects
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Molecular Sequence Data
- Peptides/immunology
- Peptides/pharmacology
- Receptors, Antigen, T-Cell, alpha-beta/antagonists & inhibitors
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/drug effects
- T-Lymphocytes/cytology
- T-Lymphocytes/immunology
- T-Lymphocytes, Cytotoxic/immunology
- Thymus Gland/cytology
- Viral Proteins/immunology
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Affiliation(s)
- O Williams
- Division of Molecular Immunology, National Institute for Medical Research, London, GB
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110
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Rabinowitz JD, Beeson C, Lyons DS, Davis MM, McConnell HM. Kinetic discrimination in T-cell activation. Proc Natl Acad Sci U S A 1996; 93:1401-5. [PMID: 8643643 PMCID: PMC39950 DOI: 10.1073/pnas.93.4.1401] [Citation(s) in RCA: 230] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We propose a quantitative model for T-cell activation in which the rate of dissociation of ligand from T-cell receptors determines the agonist and antagonist properties of the ligand. The ligands are molecular complexes between antigenic peptides and proteins of the major histocompatibility complex on the surfaces of antigen-presenting cells. Binding of ligand to receptor triggers a series of biochemical reactions in the T cell. If the ligand dissociates after these reactions are complete, the T cell receives a positive activation signal. However, dissociation of ligand after completion of the first reaction but prior to generation of the final products results in partial T-cell activation, which acts to suppress a positive response. Such a negative signal is brought about by T-cell ligands containing the variants of antigenic peptides referred to as T-cell receptor antagonists. Results of recent experiments with altered peptide ligands compare favorably with T-cell responses predicted by this model.
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Affiliation(s)
- J D Rabinowitz
- Department of Chemistry, Stanford University, CA 94305, USA
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111
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Abstract
Recently developed methodologies for the production of the soluble extracellular domains of alpha beta TCRs have allowed several biophysical characterizations. The thermodynamic and kinetic parameters associated with specific ligand interactions between the TCR and MHC-peptide complexes, as well as superantigens, are now being established. Crystallographic studies of isolated TCR fragments have yielded the structures of a V alpha domain and the two extracellular domains of a beta-chain. These investigations are beginning to allow a new visualization of antigen recognition and T-cell activation processes.
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Affiliation(s)
- D H Fremont
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
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112
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Burrows SR, Silins SL, Moss DJ, Khanna R, Misko IS, Argaet VP. T cell receptor repertoire for a viral epitope in humans is diversified by tolerance to a background major histocompatibility complex antigen. J Exp Med 1995; 182:1703-15. [PMID: 7500015 PMCID: PMC2192251 DOI: 10.1084/jem.182.6.1703] [Citation(s) in RCA: 153] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Two unusual characteristics of the memory response to the immunodominant Epstein-Barr virus (EBV) epitope FLRGRAYGL, which associates with HLA B8, have provided an unique opportunity to investigate self tolerance and T cell receptor (TCR) plasticity in humans. First, the response is exceptionally restricted, dominated by cytotoxic T lymphocytes (CTL) with identical TCR protein sequences (Argaet, V. P., C. W. Schmidt, S. R. Burrows, S. L. Silins, M. G. Kurilla, D. L. Doolan, A. Suhrbier, D. J. Moss, E. Kieff, T. B. Sculley, and I. S. Misko. 1994. J. Exp. Med. 180:2335-2340). Second, CTL expressing this receptor are cross-reactive with the alloantigen HLA B* 4402 on uninfected cells (Burrows, S. R., R. Khanna, J. M. Burrows, and D. J. Moss. 1994. J. Exp. Med. 179:1155-1161). No CTL using this conserved public TCR could be reactivated from the peripheral blood of EBV exposed individuals expressing both HLA B8 and B*4402, demonstrating the clonal inactivation of potentially self-reactive T cells in humans. A significant FLRGRAYGL-specific response was still apparent, however, and TCR sequence analysis of multiple CTL clones revealed an oligoclonal TCR repertoire for this determinant within these individuals, using diverse V and J gene segments and CDR3 regions. In addition, a significant public TCR component was identified in which several distinct alpha/beta rearrangements are shared by CTL clones from a number of unrelated HLA B8+, B*4402+ donors. The striking dominance of public TCR in the response to this EBV epitope suggests a strong genetic bias in TCR gene recombination. Fine specificity analysis using peptide analogues showed that, of six different antigen receptors for FLRGRAYGL/HLA B8, none associate closely with the peptide's full array of potential TCR contact residues. Whereas the HLA B*4402-cross-reactive receptor binds amino acids toward the COOH terminus of the peptide, others preferentially favor an NH2-terminal determinant, presumably evading an area that mimics a structure presented on HLA B*4402. Thus, tolerance to a background major histocompatibility antigen can effectively diversify the TCR repertoire for a foreign epitope by deflecting the response away from an immunodominant combination of TCR-binding residues.
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MESH Headings
- Amino Acid Sequence
- Antigens, Viral/immunology
- Base Sequence
- Cells, Cultured
- Cytotoxicity, Immunologic
- DNA Primers/chemistry
- Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor
- Gene Rearrangement, beta-Chain T-Cell Antigen Receptor
- HLA-B Antigens/immunology
- Herpesviridae Infections/immunology
- Herpesvirus 4, Human/immunology
- Humans
- Immune Tolerance
- Immunologic Memory
- Molecular Sequence Data
- Peptides/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- T-Lymphocytes, Cytotoxic/immunology
- Tumor Virus Infections/immunology
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Affiliation(s)
- S R Burrows
- Queensland Institute of Medical Research, Brisbane, Australia
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113
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Cho BK, Schodin BA, Kranz DM. Characterization of a single-chain antibody to the beta-chain of the T cell receptor. J Biol Chem 1995; 270:25819-26. [PMID: 7592766 DOI: 10.1074/jbc.270.43.25819] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In this report the VH and VL genes of the anti-T cell receptor (TCR) antibody KJ16, which recognizes the TCR V beta 8.1 and V beta 8.2 regions in mice, were cloned and expressed as a single-chain antibody (scFv) in Escherichia coli. A 29-kDa protein was obtained after renaturation from inclusion bodies. The KJ16 scFv had a relative affinity for the native TCR that was slightly higher than KJ16 Fab fragments. The scFv and Fab fragments of the KJ16 antibody, together with monovalent forms of two other anti-TCR antibodies, were evaluated as antagonists of the T cell-mediated recognition of a peptide-class I complex or of a superantigen, Staphylococcus enterotoxin B (SEB) bound to a class II product. Each of the anti-TCR antibodies was efficient at inhibiting the recognition of the SEB-class II complex. In contrast, only the clonotypic antibody, which binds to epitopes on both V beta and V alpha regions, inhibited the recognition of peptide-class I complex. We conclude that the TCR binding site for the SEB-class II ligand encompasses a larger surface area than the TCR binding site for the peptide-class I ligand.
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Affiliation(s)
- B K Cho
- Department of Biochemistry, University of Illinois, Urbana 61801-3792, USA
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