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Effect of CDR3 sequences and distal V gene residues in regulating TCR-MHC contacts and ligand specificity.

ABSTRACT: The mature T cell repertoire has the ability to orchestrate immunity to a wide range of potential pathogen challenges. This ability stems from thymic development producing individual T cell clonotypes that express TCRs with unique patterns of Ag reactivity. The Ag specificity of TCRs is created from the combinatorial pairing of one of a set of germline encoded TCR V? and V? gene segments with randomly created CDR3 sequences. How the amalgamation of germline encoded and randomly created TCR sequences results in Ag receptors with unique patterns of ligand specificity is not fully understood. Using cellular, biophysical, and structural analyses, we show that CDR3? residues can modulate the geometry in which TCRs bind peptide-MHC (pMHC), governing whether and how germline encoded TCR V? and V? residues interact with MHC. In addition, a CDR1? residue that is positioned distal to the TCR-pMHC binding interface is shown to contribute to the peptide specificity of T cells. These findings demonstrate that the specificity of individual T cell clonotypes arises not only from TCR residues that create direct contacts with the pMHC, but also from a collection of indirect effects that modulate how TCR residues are used to bind pMHC.

SUBMITTER: Stadinski BD

PROVIDER: S-EPMC4097884 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

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Effect of CDR3 sequences and distal V gene residues in regulating TCR-MHC contacts and ligand specificity.

Stadinski Brian D BD Trenh Peter P Duke Brian B Huseby Priya G PG Li Guoqi G Stern Lawrence J LJ Huseby Eric S ES

Journal of immunology (Baltimore, Md. : 1950) 20140509 12

The mature T cell repertoire has the ability to orchestrate immunity to a wide range of potential pathogen challenges. This ability stems from thymic development producing individual T cell clonotypes that express TCRs with unique patterns of Ag reactivity. The Ag specificity of TCRs is created from the combinatorial pairing of one of a set of germline encoded TCR Vα and Vβ gene segments with randomly created CDR3 sequences. How the amalgamation of germline encoded and randomly created TCR seque ...[more]

PMID: 24813203

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Project description:BackgroundCD4 T lymphocyte activation requires T cell receptor (TCR) engagement by peptide/MHC (major histocompatibility complex) (pMHC). The TCR complementarity-determining region 3 (CDR3) contains variable ? and ? loops critical for pMHC recognition. During any immune response, tuning of TCR usage through progressive clonal selection occurs. Th1 and Th2 cells operate at different avidities for activation and display distinct transcriptional programs, although polarization may be plastic, influenced by pathogens and cytokines. We therefore hypothesized that CDR3?? sequence features may intrinsically influence CD4 phenotype during progression of a response.ResultsWe show that CD4 polarization involves distinct CDR3? usage: Th1 and Th17 cells favored short TCR CDR3? sequences of 12 and 11 amino acids, respectively, while Th2 cells favored elongated CDR3? loops of 14 amino acids, with lower predicted affinity. The dominant Th2- and Th1-derived TCR? sequences with 14 amino acid CDR3 loops and 12 amino acid CDR3 loops, respectively, were expressed in TCR transgenics. The functional impact of these TCR? transgenes was assessed after in vivo priming with a peptide/adjuvant. The short, Th1-derived receptor transgenic T cell lines made IFN?, but not IL-4, 5 or 13, while the elongated, Th2-derived receptor transgenic T cell lines made little or no IFN?, but increased IL-4, 5 and 13 with progressive re-stimulations, mirrored by GATA-3 up-regulation. T cells from primed Th2 TCR? transgenics selected dominant TCR V? expansions, allowing us to generate TCR?? transgenics carrying the favored, Th2-derived receptor heterodimer. Primed T cells from TCR?? transgenics made little or no IL-17 or IFN?, but favored IL-9 after priming with Complete Freund's adjuvant and IL-4, 5, 9, 10 and 13 after priming with incomplete Freund's. In tetramer-binding studies, this transgenic receptor showed low binding avidity for pMHC and polarized T cell lines show TCR avidity for Th17 > Th1 > Th2. While transgenic expression of a Th2-derived, 'elongated' TCR-CDR3? and the TCR?? pair, clearly generated a program shifted away from Th1 immunity and with low binding avidity, cytokine-skewing could be over-ridden by altering peptide challenge dose.ConclusionWe propose that selection from responding clones with distinctive TCRs on the basis of functional avidity can direct a preference away from Th1 effector responses, favoring Th2 cytokines.

Dataset Information

Effect of CDR3 sequences and distal V gene residues in regulating TCR-MHC contacts and ligand specificity.

Publications

Effect of CDR3 sequences and distal V gene residues in regulating TCR-MHC contacts and ligand specificity.

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