Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Front Immunol ; 8: 1503, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29209312

RESUMO

Serial accumulation of mutations to fixation in the SLYNTVATL (SL9) immunodominant, HIV p17 Gag-derived, HLA A2-restricted cytotoxic T lymphocyte epitope produce the SLFNTIAVL triple mutant "ultimate" escape variant. These mutations in solvent-exposed residues are believed to interfere with TCR recognition, although confirmation has awaited structural verification. Here, we solved a TCR co-complex structure with SL9 and the triple escape mutant to determine the mechanism of immune escape in this eminent system. We show that, in contrast to prevailing hypotheses, the main TCR contact residue is 4N and the dominant mechanism of escape is not via lack of TCR engagement. Instead, mutation of solvent-exposed residues in the peptide destabilise the peptide-HLA and reduce peptide density at the cell surface. These results highlight the extraordinary lengths that HIV employs to evade detection by high-affinity TCRs with a broad peptide-binding footprint and necessitate re-evaluation of this exemplar model of HIV TCR escape.

2.
Immunol Cell Biol ; 93(7): 625-33, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25801351

RESUMO

Basic parameters of the naive antigen (Ag)-specific T-cell repertoire in humans remain poorly defined. Systematic characterization of this 'ground state' immunity in comparison with memory will allow a better understanding of clonal selection during immune challenge. Here, we used high-definition cell isolation from umbilical cord blood samples to establish the baseline frequency, phenotype and T-cell antigen receptor (TCR) repertoire of CD8(+) T-cell precursor populations specific for a range of viral and self-derived Ags. Across the board, these precursor populations were phenotypically naive and occurred with hierarchical frequencies clustered by Ag specificity. The corresponding patterns of TCR architecture were highly ordered and displayed partial overlap with adult memory, indicating biased structuring of the T-cell repertoire during Ag-driven selection. Collectively, these results provide new insights into the complex nature and dynamics of the naive T-cell compartment.


Assuntos
Autoantígenos/imunologia , Linfócitos T CD8-Positivos/imunologia , Seleção Clonal Mediada por Antígeno , Sangue Fetal/imunologia , Células-Tronco Hematopoéticas/imunologia , Fosfoproteínas/imunologia , Receptores de Antígenos de Linfócitos T/imunologia , Especificidade do Receptor de Antígeno de Linfócitos T , Proteínas da Matriz Viral/imunologia , Adulto , Envelhecimento/imunologia , Dasatinibe/farmacologia , Sangue Fetal/citologia , Citometria de Fluxo , Antígenos HLA/imunologia , Humanos , Memória Imunológica , Separação Imunomagnética , Imunofenotipagem , Recém-Nascido , Fragmentos de Peptídeos/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/genética
3.
J Biol Chem ; 289(2): 628-38, 2014 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-24196962

RESUMO

αß T-cell receptors (TCRs) engage antigens using complementarity-determining region (CDR) loops that are either germ line-encoded (CDR1 and CDR2) or somatically rearranged (CDR3). TCR ligands compose a presentation platform (major histocompatibility complex (MHC)) and a variable antigenic component consisting of a short "foreign" peptide. The sequence of events when the TCR engages its peptide-MHC (pMHC) ligand remains unclear. Some studies suggest that the germ line elements of the TCR engage the MHC prior to peptide scanning, but this order of binding is difficult to reconcile with some TCR-pMHC structures. Here, we used TCRs that exhibited enhanced pMHC binding as a result of mutations in either CDR2 and/or CDR3 loops, that bound to the MHC or peptide, respectively, to dissect the roles of these loops in stabilizing TCR-pMHC interactions. Our data show that TCR-peptide interactions play a strongly dominant energetic role providing a binding mode that is both temporally and energetically complementary with a system requiring positive selection by self-pMHC in the thymus and rapid recognition of non-self-pMHC in the periphery.


Assuntos
Regiões Determinantes de Complementaridade/metabolismo , Antígenos HLA/metabolismo , Peptídeos/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Sequência de Aminoácidos , Ligação Competitiva , Regiões Determinantes de Complementaridade/química , Regiões Determinantes de Complementaridade/genética , Cristalografia por Raios X , Antígenos HLA/química , Antígenos HLA/genética , Antígeno HLA-A2/química , Antígeno HLA-A2/genética , Antígeno HLA-A2/metabolismo , Humanos , Cinética , Ligantes , Modelos Moleculares , Dados de Sequência Molecular , Mutação , Oligopeptídeos/química , Oligopeptídeos/metabolismo , Peptídeos/química , Ligação Proteica , Estrutura Terciária de Proteína , Receptores de Antígenos de Linfócitos T/química , Receptores de Antígenos de Linfócitos T/genética , Especificidade do Receptor de Antígeno de Linfócitos T
4.
J Biol Chem ; 288(26): 18766-75, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23698002

RESUMO

The T-cell receptor (TCR) recognizes peptides bound to major histocompatibility molecules (MHC) and allows T-cells to interrogate the cellular proteome for internal anomalies from the cell surface. The TCR contacts both MHC and peptide in an interaction characterized by weak affinity (KD = 100 nM to 270 µM). We used phage-display to produce a melanoma-specific TCR (α24ß17) with a 30,000-fold enhanced binding affinity (KD = 0.6 nM) to aid our exploration of the molecular mechanisms utilized to maintain peptide specificity. Remarkably, although the enhanced affinity was mediated primarily through new TCR-MHC contacts, α24ß17 remained acutely sensitive to modifications at every position along the peptide backbone, mimicking the specificity of the wild type TCR. Thermodynamic analyses revealed an important role for solvation in directing peptide specificity. These findings advance our understanding of the molecular mechanisms that can govern the exquisite peptide specificity characteristic of TCR recognition.


Assuntos
Regulação Neoplásica da Expressão Gênica , Melanoma/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Especificidade do Receptor de Antígeno de Linfócitos T , Alanina , Biotinilação , Cristalografia por Raios X , Humanos , Ligação de Hidrogênio , Complexo Principal de Histocompatibilidade , Conformação Molecular , Mutação , Biblioteca de Peptídeos , Peptídeos/metabolismo , Ligação Proteica , Solventes , Ressonância de Plasmônio de Superfície , Termodinâmica , Água
5.
Blood ; 121(7): 1112-23, 2013 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-23255554

RESUMO

αß-TCRs expressed at the CD8(+) T-cell surface interact with short peptide fragments (p) bound to MHC class I molecules (pMHCI). The TCR/pMHCI interaction is pivotal in all aspects of CD8(+) T-cell immunity. However, the rules that govern the outcome of TCR/pMHCI engagement are not entirely understood, and this is a major barrier to understanding the requirements for both effective immunity and vaccination. In the present study, we discovered an unexpected feature of the TCR/pMHCI interaction by showing that any given TCR exhibits an explicit preference for a single MHCI-peptide length. Agonists of nonpreferred length were extremely rare, suboptimal, and often entirely distinct in sequence. Structural analysis indicated that alterations in peptide length have a major impact on antigenic complexity, to which individual TCRs are unable to adapt. This novel finding demonstrates that the outcome of TCR/pMHCI engagement is determined by peptide length in addition to the sequence identity of the MHCI-bound peptide. Accordingly, the effective recognition of pMHCI Ag, which is a prerequisite for successful CD8(+) T-cell immunity and protective vaccination, can only be achieved by length-matched Ag-specific CD8(+) T-cell clonotypes.


Assuntos
Antígenos de Histocompatibilidade Classe I/metabolismo , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/metabolismo , Sequência de Aminoácidos , Apresentação de Antígeno , Antígenos/química , Antígenos/genética , Antígenos/imunologia , Linfócitos T CD8-Positivos/imunologia , Células Clonais , Humanos , Imunidade Celular , Modelos Moleculares , Oligopeptídeos/química , Oligopeptídeos/genética , Oligopeptídeos/imunologia , Fragmentos de Peptídeos/genética , Biblioteca de Peptídeos
6.
J Immunol Methods ; 382(1-2): 203-10, 2012 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-22705983

RESUMO

The interaction between the clonotypic αß T cell receptor (TCR), expressed on the T cell surface, and peptide-major histocompatibility complex (pMHC) molecules, expressed on the target cell surface, governs T cell mediated autoimmunity and immunity against pathogens and cancer. Structural investigations of this interaction have been limited because of the challenges inherent in the production of good quality TCR/pMHC protein crystals. Here, we report the development of an 'intelligently designed' crystallization screen that reproducibly generates high quality TCR/pMHC complex crystals suitable for X-ray crystallographic studies, thereby reducing protein consumption. Over the last 2 years, we have implemented this screen to produce 32 T cell related protein structures at high resolution, substantially contributing to the current immune protein database. Protein crystallography, used to study this interaction, has already extended our understanding of the molecular rules that govern T cell immunity. Subsequently, these data may help to guide the intelligent design of T cell based therapies that target human diseases, underlining the importance of developing optimized approaches for crystallizing novel TCR/pMHC complexes.


Assuntos
Cristalização/métodos , Complexo Principal de Histocompatibilidade , Peptídeos/química , Receptores de Antígenos de Linfócitos T/química , Cristalografia por Raios X , Humanos , Complexo Principal de Histocompatibilidade/imunologia , Peptídeos/imunologia , Conformação Proteica , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , Linfócitos T/química , Linfócitos T/imunologia
7.
J Immunol ; 187(2): 654-63, 2011 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-21677135

RESUMO

CD8(+) T cells recognize immunogenic peptides presented at the cell surface bound to MHCI molecules. Ag recognition involves the binding of both TCR and CD8 coreceptor to the same peptide-MHCI (pMHCI) ligand. Specificity is determined by the TCR, whereas CD8 mediates effects on Ag sensitivity. Anti-CD8 Abs have been used extensively to examine the role of CD8 in CD8(+) T cell activation. However, as previous studies have yielded conflicting results, it is unclear from the literature whether anti-CD8 Abs per se are capable of inducing effector function. In this article, we report on the ability of seven monoclonal anti-human CD8 Abs to activate six human CD8(+) T cell clones with a total of five different specificities. Six of seven anti-human CD8 Abs tested did not activate CD8(+) T cells. In contrast, one anti-human CD8 Ab, OKT8, induced effector function in all CD8(+) T cells examined. Moreover, OKT8 was found to enhance TCR/pMHCI on-rates and, as a consequence, could be used to improve pMHCI tetramer staining and the visualization of Ag-specific CD8(+) T cells. The anti-mouse CD8 Abs, CT-CD8a and CT-CD8b, also activated CD8(+) T cells despite opposing effects on pMHCI tetramer staining. The observed heterogeneity in the ability of anti-CD8 Abs to trigger T cell effector function provides an explanation for the apparent incongruity observed in previous studies and should be taken into consideration when interpreting results generated with these reagents. Furthermore, the ability of Ab-mediated CD8 engagement to deliver an activation signal underscores the importance of CD8 in CD8(+) T cell signaling.


Assuntos
Anticorpos/fisiologia , Antígenos CD8/imunologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Citotoxicidade Imunológica , Antígenos HLA-A/química , Peptídeos/química , Receptores de Antígenos de Linfócitos T/deficiência , Anticorpos/metabolismo , Linfócitos T CD8-Positivos/citologia , Células Clonais , Antígenos HLA-A/imunologia , Antígeno HLA-A2 , Humanos , Imunofenotipagem , Ligantes , Peptídeos/análise , Peptídeos/imunologia , Receptores de Antígenos de Linfócitos T/imunologia , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais/imunologia , Coloração e Rotulagem , Ressonância de Plasmônio de Superfície
8.
PLoS Pathog ; 6(11): e1001198, 2010 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-21124993

RESUMO

Despite the ∼10(18) αß T cell receptor (TCR) structures that can be randomly manufactured by the human thymus, some surface more frequently than others. The pinnacles of this distortion are public TCRs, which exhibit amino acid-identical structures across different individuals. Public TCRs are thought to result from both recombinatorial bias and antigen-driven selection, but the mechanisms that underlie inter-individual TCR sharing are still largely theoretical. To examine this phenomenon at the atomic level, we solved the co-complex structure of one of the most widespread and numerically frequent public TCRs in the human population. The archetypal AS01 public TCR recognizes an immunodominant BMLF1 peptide, derived from the ubiquitous Epstein-Barr virus, bound to HLA-A*0201. The AS01 TCR was observed to dock in a diagonal fashion, grasping the solvent exposed peptide crest with two sets of complementarity-determining region (CDR) loops, and was fastened to the peptide and HLA-A*0201 platform with residue sets found only within TCR genes biased in the public response. Computer simulations of a random V(D)J recombination process demonstrated that both TCRα and TCRß amino acid sequences could be manufactured easily, thereby explaining the prevalence of this receptor across different individuals. Interestingly, the AS01 TCR was encoded largely by germline DNA, indicating that the TCR loci already comprise gene segments that specifically recognize this ancient pathogen. Such pattern recognition receptor-like traits within the αß TCR system further blur the boundaries between the adaptive and innate immune systems.


Assuntos
Antígenos Virais/imunologia , Antígenos HLA-A/imunologia , Infecções por Herpesviridae/imunologia , Herpesvirus Humano 4/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/química , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Sequência de Aminoácidos , Linfócitos T CD8-Positivos , Simulação por Computador , Cristalização , Cristalografia por Raios X , Citotoxicidade Imunológica , Antígeno HLA-A2 , Infecções por Herpesviridae/metabolismo , Infecções por Herpesviridae/virologia , Humanos , Tolerância Imunológica , Dados de Sequência Molecular , Conformação Proteica , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Recombinação Genética , Homologia de Sequência de Aminoácidos , Ressonância de Plasmônio de Superfície
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...