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Abstract
αβ T cells are an integral part of protective immunity against pathogens. After precursor cells arise in the adult bone marrow or fetal liver, they migrate to the thymus where they rearrange their T-cell receptor genes (TCR) and undergo selection on the basis of their interactions with ligands expressed by thymic stroma and other cells. Those that survive then exit the thymus to populate the peripheral immune compartment, where they patrol the blood and lymphoid systems. The composition of this pre-immune peripheral repertoire is critically important in determining the robustness of an immune response. In both mice and humans, the magnitude and diversity of a response are directly correlated with the frequency of precursor T cells. Equally relevant are the functional characteristics of these lymphocytes. Engagement of a specific antigen to the TCR activates signaling pathways in the naive T cell that result in cellular proliferation and the acquisition of particular effector functions. A portion of these persist following the resolution of infection and become memory cells. These memory cells can mount a faster and stronger response when they encounter the same antigen at a later time. As the molecular basis for TCR ligand interaction has become better defined, it is clear that some T cells can recognize multiple distinct ligands and therefore T-cell memory developed by exposure to one ligand may play a significant role in the response to a different antigen. Thus, there is an increasing focus on understanding how exposure to related or unrelated antigens influences the T-cell repertoire and impacts subsequent immunity. In this review, we discuss the issue of TCR cross-reactivity in the development of memory phenotype CD4(+) T cells and the implications for pathogen-specific responses. We review both the human and mouse data and discuss the therapeutic implications of these findings in the contexts of infection and vaccination.
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Affiliation(s)
- Laura F Su
- The Division of Immunology and Rheumatology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
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52
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The promised land of human immunology. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2014; 78:203-13. [PMID: 24638855 DOI: 10.1101/sqb.2013.78.022905] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Advances in technology and data analysis have made it possible to take a new look at human immunology. These advances run the gamut from systems biology approaches, which are likely in the vanguard of how we can start "to put the pieces together" of immune function, to a deeper understanding of specific diseases and vaccines and the immune repertoire. In our own experience, we have also found that asking simple questions about human immunity has often given us very surprising answers, causing a rethink of established dogma. Thus, we have developed a new perspective on the nature of the αβ TCR repertoire and also the likely role of T-cell repertoire (TCR) cross-reactivity in generating T memory independent of specific antigen interactions. These findings show that human immunology is not just a necessary step for "translating" basic immunology to treat diseases or develop better vaccines, but is also an important complement to the inbred mouse model.
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53
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Abstract
The mammalian immune system has evolved to display peptides derived from microbial antigens to immune effector cells. Liberated from the intact antigens through distinct proteolytic mechanisms, these peptides are subsequently transported to the cell surface while bound to chaperone-like receptors known as major histocompatibility complex molecules. These complexes are then scrutinized by T-cells that express receptors with specificity for specific major histocompatibility complex-peptide complexes. In normal uninfected cells, this process of antigen processing and presentation occurs continuously, with the resultant array of self-antigen-derived peptides displayed on the surface of these cells. Changes in this cellular peptide array alert the immune system to changes in the intracellular environment that may be associated with infection, oncogenesis or other abnormal cellular processes, resulting in a cascade of events that result in the elimination of the abnormal cell. Since peptides play such an essential role in informing the immune system of infection with viral or microbial pathogens and the transformation of cells in malignancy, the tools of proteomics, in particular mass spectrometry, are ideally suited to study these immune responses at a molecular level. Recent advances in studies of immune responses that have utilized mass spectrometry and associated technologies are reviewed. The authors gaze into the future and look at current challenges and where proteomics will impact in immunology over the next 5 years.
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Affiliation(s)
- Nicholas A Williamson
- The University of Melbourne, Department of Biochemistry & Molecular Biology, The Bio21 Molecular Science & Biotechnology Institute, 3010, Victoria, Australia.
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54
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Zarnitsyna VI, Evavold BD, Schoettle LN, Blattman JN, Antia R. Estimating the diversity, completeness, and cross-reactivity of the T cell repertoire. Front Immunol 2013; 4:485. [PMID: 24421780 PMCID: PMC3872652 DOI: 10.3389/fimmu.2013.00485] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 12/10/2013] [Indexed: 11/13/2022] Open
Abstract
In order to recognize and combat a diverse array of pathogens the immune system has a large repertoire of T cells having unique T cell receptors (TCRs) with only a few clones specific for any given antigen. We discuss how the number of different possible TCRs encoded in the genome (the potential repertoire) and the number of different TCRs present in an individual (the realized repertoire) can be measured. One puzzle is that the potential repertoire greatly exceeds the realized diversity of naïve T cells within any individual. We show that the existing hypotheses fail to explain why the immune system has the potential to generate far more diversity than is used in an individual, and propose an alternative hypothesis of “evolutionary sloppiness.” Another immunological puzzle is why mice and humans have similar repertoires even though humans have over 1000-fold more T cells. We discuss how the idea of the “protecton,” the smallest unit of protection, might explain this discrepancy and estimate the size of “protecton” based on available precursor frequencies data. We then consider T cell cross-reactivity – the ability of a T cell clone to respond to more than one epitope. We extend existing calculations to estimate the extent of expected cross-reactivity between the responses to different pathogens. Our results are consistent with two observations: a low probability of observing cross-reactivity between the immune responses to two randomly chosen pathogens; and the ensemble of memory cells being sufficiently diverse to generate cross-reactive responses to new pathogens.
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Affiliation(s)
| | - Brian D Evavold
- Department of Microbiology and Immunology, Emory University , Atlanta, GA , USA
| | - Louis N Schoettle
- Center for Infectious Diseases and Vaccinology, School of Life Sciences, Arizona State University , Tempe, AZ , USA
| | - Joseph N Blattman
- Center for Infectious Diseases and Vaccinology, School of Life Sciences, Arizona State University , Tempe, AZ , USA
| | - Rustom Antia
- Department of Biology, Emory University , Atlanta, GA , USA
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55
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A peptide's perspective on antigen presentation to the immune system. Nat Chem Biol 2013; 9:769-75. [DOI: 10.1038/nchembio.1391] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 10/16/2013] [Indexed: 12/20/2022]
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56
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Olsen LR, Kudahl UJ, Simon C, Sun J, Schönbach C, Reinherz EL, Zhang GL, Brusic V. BlockLogo: visualization of peptide and sequence motif conservation. J Immunol Methods 2013; 400-401:37-44. [PMID: 24001880 DOI: 10.1016/j.jim.2013.08.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 08/20/2013] [Accepted: 08/25/2013] [Indexed: 12/21/2022]
Abstract
BlockLogo is a web-server application for the visualization of protein and nucleotide fragments, continuous protein sequence motifs, and discontinuous sequence motifs using calculation of block entropy from multiple sequence alignments. The user input consists of a multiple sequence alignment, selection of motif positions, type of sequence, and output format definition. The output has BlockLogo along with the sequence logo, and a table of motif frequencies. We deployed BlockLogo as an online application and have demonstrated its utility through examples that show visualization of T-cell epitopes and B-cell epitopes (both continuous and discontinuous). Our additional example shows a visualization and analysis of structural motifs that determine the specificity of peptide binding to HLA-DR molecules. The BlockLogo server also employs selected experimentally validated prediction algorithms to enable on-the-fly prediction of MHC binding affinity to 15 common HLA class I and class II alleles as well as visual analysis of discontinuous epitopes from multiple sequence alignments. It enables the visualization and analysis of structural and functional motifs that are usually described as regular expressions. It provides a compact view of discontinuous motifs composed of distant positions within biological sequences. BlockLogo is available at: http://research4.dfci.harvard.edu/cvc/blocklogo/ and http://met-hilab.bu.edu/blocklogo/.
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Affiliation(s)
- Lars Rønn Olsen
- Cancer Vaccine Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA; Bioinformatics Centre, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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57
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Holland CJ, Cole DK, Godkin A. Re-Directing CD4(+) T Cell Responses with the Flanking Residues of MHC Class II-Bound Peptides: The Core is Not Enough. Front Immunol 2013; 4:172. [PMID: 23847615 PMCID: PMC3696884 DOI: 10.3389/fimmu.2013.00172] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 06/14/2013] [Indexed: 11/17/2022] Open
Abstract
Recombinant αβ T cell receptors, expressed on T cell membranes, recognize short peptides presented at the cell surface in complex with MHC molecules. There are two main subsets of αβ T cells: CD8(+) T cells that recognize mainly cytosol-derived peptides in the context of MHC class I (pMHC-I), and CD4(+) T cells that recognize peptides usually derived from exogenous proteins presented by MHC class II (pMHC-II). Unlike the more uniform peptide lengths (usually 8-13mers) bound in the MHC-I closed groove, MHC-II presented peptides are of a highly variable length. The bound peptides consist of a core bound 9mer (reflecting the binding motif for the particular MHC-II type) but with variable peptide flanking residues (PFRs) that can extend from both the N- and C-terminus of the MHC-II binding groove. Although pMHC-I and pMHC-II play a virtually identical role during T cell responses (T cell antigen presentation) and are very similar in overall conformation, there exist a number of subtle but important differences that may govern the functional dichotomy observed between CD8(+) and CD4(+) T cells. Here, we provide an overview of the impact of structural differences between pMHC-I and pMHC-II and the molecular interactions with the T cell receptor including the functional importance of MHC-II PFRs. We consider how factors such as anatomical location, inflammatory milieu, and particular types of antigen presenting cell might, in theory, contribute to the quantitative (i.e., pMHC ligand frequency) as well as qualitative (i.e., variable PFR) nature of peptide epitopes, and hence offer a means of control and influence of a CD4(+) T cell response. Lastly, we review our recent findings showing how modifications to MHC-II PFRs can modify CD4(+) T cell antigen recognition. These findings may have novel applications for the development of CD4(+) T cell peptide vaccines and diagnostics.
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Affiliation(s)
| | - David K. Cole
- Institute of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK
| | - Andrew Godkin
- Institute of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK
- Department of Integrated Medicine, University Hospital of Wales, Cardiff, UK
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58
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Cole DK, Sami M, Scott DR, Rizkallah PJ, Borbulevych OY, Todorov PT, Moysey RK, Jakobsen BK, Boulter JM, Baker BM, Yi Li. Increased Peptide Contacts Govern High Affinity Binding of a Modified TCR Whilst Maintaining a Native pMHC Docking Mode. Front Immunol 2013; 4:168. [PMID: 23805144 PMCID: PMC3693486 DOI: 10.3389/fimmu.2013.00168] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 06/12/2013] [Indexed: 12/15/2022] Open
Abstract
Natural T cell receptors (TCRs) generally bind to their cognate pMHC molecules with weak affinity and fast kinetics, limiting their use as therapeutic agents. Using phage display, we have engineered a high affinity version of the A6 wild-type TCR (A6wt), specific for the human leukocyte antigen (HLA-A∗0201) complexed with human T cell lymphotropic virus type 111–19 peptide (A2-Tax). Mutations in just 4 residues in the CDR3β loop region of the A6wt TCR were selected that improved binding to A2-Tax by nearly 1000-fold. Biophysical measurements of this mutant TCR (A6c134) demonstrated that the enhanced binding was derived through favorable enthalpy and a slower off-rate. The structure of the free A6c134 TCR and the A6c134/A2-Tax complex revealed a native binding mode, similar to the A6wt/A2-Tax complex. However, concordant with the more favorable binding enthalpy, the A6c134 TCR made increased contacts with the Tax peptide compared with the A6wt/A2-Tax complex, demonstrating a peptide-focused mechanism for the enhanced affinity that directly involved the mutated residues in the A6c134 TCR CDR3β loop. This peptide-focused enhanced TCR binding may represent an important approach for developing antigen specific high affinity TCR reagents for use in T cell based therapies.
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Affiliation(s)
- David K Cole
- Cardiff University School of Medicine, Heath Park , Cardiff , UK
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59
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The regulatory power of glycans and their binding partners in immunity. Trends Immunol 2013; 34:290-8. [PMID: 23485517 DOI: 10.1016/j.it.2013.01.006] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 01/14/2013] [Accepted: 01/28/2013] [Indexed: 02/06/2023]
Abstract
Glycans and glycan-binding proteins are central to a properly functioning immune system. Perhaps the best known example of this is the selectin family of surface proteins that are primarily found on leukocytes, and which bind to endothelial glycans near sites of infection or inflammation and enable extravasation into tissues. In the past decade, however, several other immune pathways that are dependent on or sensitive to changes in glycan-mediated mechanisms have been revealed. These include antibody function, apoptosis, T helper (Th)1 versus Th2 skewing, T cell receptor signaling, and MHC class II antigen presentation. Here, we highlight how regulated changes in protein glycosylation both at the cell surface and on secreted glycoproteins can positively and negatively modulate the immune response.
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60
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Yin Y, Li Y, Mariuzza RA. Structural basis for self-recognition by autoimmune T-cell receptors. Immunol Rev 2013; 250:32-48. [PMID: 23046121 DOI: 10.1111/imr.12002] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
T-cell receptors (TCRs) recognize peptides presented by major histocompatibility complex molecules (pMHC) to discriminate between foreign and self-antigens. Whereas T-cell recognition of foreign peptides is essential for protection against microbial pathogens, recognition of self-peptides by T cells that have escaped negative selection in the thymus can lead to autoimmune disease. Structural studies of autoimmune TCR-pMHC complexes have provided insights into the mechanisms underlying self-recognition and escape from thymic deletion. Two broad categories of self-reactive TCRs can be clearly distinguished: (i) TCRs with altered binding topologies to self-pMHC and (ii) TCRs that bind self-pMHC in the canonical diagonal orientation, but where there are structural defects or suboptimal anchors in the self-ligand. For both categories, however, the overall stability of the autoimmune TCR-pMHC complex is markedly reduced compared to anti-microbial complexes, allowing the autoreactive T cells to evade negative selection, yet retain the ability to be activated by self-antigens in target organs. Additionally, the structures provide insights into TCR cross-reactivity, which can contribute to autoimmunity by increasing the likelihood of self-pMHC recognition. Efforts are now underway to understand the impact of structural alterations in autoimmune TCR-pMHC complexes on higher order assemblies involved in TCR signaling, as well as on immunological synapse formation.
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Affiliation(s)
- Yiyuan Yin
- Department of Antibody Engineering, Genentech, South San Francisco, CA, USA
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61
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Yin L, Scott-Browne J, Kappler JW, Gapin L, Marrack P. T cells and their eons-old obsession with MHC. Immunol Rev 2013; 250:49-60. [PMID: 23046122 PMCID: PMC3963424 DOI: 10.1111/imr.12004] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
T cells bearing receptors made up of α and β chains (TCRs) usually react with peptides bound to major histocompatibility complex proteins (MHC). This bias could be imposed by positive selection, the phenomenon that selects thymocytes to mature into T cells only if the TCRs they bear react with low but appreciable affinity with MHC + peptide combinations in the thymus cortex. However, it is also possible that the polypeptides of TCRs themselves do not have random specificities but rather are biased toward reaction with MHC. Evolution would therefore have selected for a collection of TCR variable elements that are prone to react with MHC. If this were to be so, positive selection would act on thymocytes bearing a pre biased collection of TCRs to pick out those that react to some extent, but not too well, with self MHC + self-peptides. A problem with studies of this evolutionary idea is the fact that there are many TCR variable elements and that these differ considerably in the amino acids with which they contact MHC. However, recent experiments by our group and others suggest that one group of TCR variable elements, those related to the mouse Vβ8 family, has amino acids in their CDR2 regions that consistently bind a particular site on an MHC α-helix. Other groups of variable elements may use different patterns of amino acids to achieve the same goal. Mutation of these amino acids reduces the ability of T cells and thymocytes to react with MHC. These amino acids are present in the variable regions of distantly related species such as sharks and human. Overall the data indicate that TCR elements have indeed been selected by evolution to react with MHC proteins. Many mysteries about TCRs remain to be solved, including the nature of auto-recognition, the basis of MHC allele specificity, and the very nature and complexity of TCRs on mature T cells.
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Affiliation(s)
- Lei Yin
- Integrated Department of Immunology, HHMI, National Jewish Health, Denver, CO, USA
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62
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Mandl JN, Monteiro JP, Vrisekoop N, Germain RN. T cell-positive selection uses self-ligand binding strength to optimize repertoire recognition of foreign antigens. Immunity 2013; 38:263-274. [PMID: 23290521 PMCID: PMC3785078 DOI: 10.1016/j.immuni.2012.09.011] [Citation(s) in RCA: 226] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 09/28/2012] [Indexed: 01/19/2023]
Abstract
Developing T cells express diverse antigen receptors whose specificities are not prematched to the foreign antigens they eventually encounter. Past experiments have revealed that thymocytes must productively signal in response to self antigens to mature and enter the peripheral T cell pool (positive selection), but how this process enhances effective mature T cell responses to foreign antigen is not fully understood. Here we have documented an unsuspected connection between thymic recognition events and foreign antigen-driven T cell responses. We find that the strength of self-reactivity is a clone-specific property unexpectedly directly related to the strength of T cell receptor (TCR) binding to presented foreign antigen. T cells with receptors showing stronger interaction with self dominate in responses to infections and accumulate in aging individuals, revealing that positive selection contributes to effective immunity by skewing the mature TCR repertoire toward highly effective recognition of pathogens that pose a danger to the host.
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Affiliation(s)
- Judith N. Mandl
- Lymphocyte Biology Section, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892 USA
| | - João P. Monteiro
- Lymphocyte Biology Section, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892 USA
| | - Nienke Vrisekoop
- Lymphocyte Biology Section, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892 USA
| | - Ronald N. Germain
- Lymphocyte Biology Section, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892 USA
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63
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Su LF, Kidd BA, Han A, Kotzin JJ, Davis MM. Virus-specific CD4(+) memory-phenotype T cells are abundant in unexposed adults. Immunity 2013; 38:373-83. [PMID: 23395677 DOI: 10.1016/j.immuni.2012.10.021] [Citation(s) in RCA: 343] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 10/25/2012] [Indexed: 11/29/2022]
Abstract
Although T cell memory is generally thought to require direct antigen exposure, we found an abundance of memory-phenotype cells (20%-90%, averaging over 50%) of CD4(+) T cells specific to viral antigens in adults who had never been infected. These cells express the appropriate memory markers and genes, rapidly produce cytokines, and have clonally expanded. In contrast, the same T cell receptor (TCR) specificities in newborns are almost entirely naïve, which might explain the vulnerability of young children to infections. One mechanism for this phenomenon is TCR cross-reactivity to environmental antigens, and in support of this, we found extensive cross-recognition by HIV-1 and influenza-reactive T lymphocytes to other microbial peptides and expansion of one of these after influenza vaccination. Thus, the presence of these memory-phenotype T cells has significant implications for immunity to novel pathogens, child and adult health, and the influence of pathogen-rich versus hygienic environments.
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Affiliation(s)
- Laura F Su
- Division of Immunology and Rheumatology, Stanford University School of Medicine, Stanford, CA 94304, USA
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64
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Su CTT, Schönbach C, Kwoh CK. Molecular docking analysis of 2009-H1N1 and 2004-H5N1 influenza virus HLA-B*4405-restricted HA epitope candidates: implications for TCR cross-recognition and vaccine development. BMC Bioinformatics 2013; 14 Suppl 2:S21. [PMID: 23368875 PMCID: PMC3549837 DOI: 10.1186/1471-2105-14-s2-s21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Background The pandemic 2009-H1N1 influenza virus circulated in the human population and caused thousands deaths worldwide. Studies on pandemic influenza vaccines have shown that T cell recognition to conserved epitopes and cross-reactive T cell responses are important when new strains emerge, especially in the absence of antibody cross-reactivity. In this work, using HLA-B*4405 and DM1-TCR structure model, we systematically generated high confidence conserved 2009-H1N1 T cell epitope candidates and investigated their potential cross-reactivity against H5N1 avian flu virus. Results Molecular docking analysis of differential DM1-TCR recognition of the 2009-H1N1 epitope candidates yielded a mosaic epitope (KEKMNTEFW) and potential H5N1 HA cross-reactive epitopes that could be applied as multivalent peptide towards influenza A vaccine development. Structural models of TCR cross-recognition between 2009-H1N1 and 2004-H5N1 revealed steric and topological effects of TCR contact residue mutations on TCR binding affinity. Conclusions The results are novel with regard to HA epitopes and useful for developing possible vaccination strategies against the rapidly changing influenza viruses. Yet, the challenge of identifying epitope candidates that result in heterologous T cell immunity under natural influenza infection conditions can only be overcome if more structural data on the TCR repertoire become available.
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Affiliation(s)
- Chinh T T Su
- Bioinformatics Research Centre, School of Computer Engineering, Nanyang Technological University, Singapore
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65
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Reddy Chichili VP, Kumar V, Sivaraman J. Linkers in the structural biology of protein-protein interactions. Protein Sci 2013; 22:153-67. [PMID: 23225024 DOI: 10.1002/pro.2206] [Citation(s) in RCA: 222] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 11/08/2012] [Accepted: 11/13/2012] [Indexed: 12/14/2022]
Abstract
Linkers or spacers are short amino acid sequences created in nature to separate multiple domains in a single protein. Most of them are rigid and function to prohibit unwanted interactions between the discrete domains. However, Gly-rich linkers are flexible, connecting various domains in a single protein without interfering with the function of each domain. The advent of recombinant DNA technology made it possible to fuse two interacting partners with the introduction of artificial linkers. Often, independent proteins may not exist as stable or structured proteins until they interact with their binding partner, following which they gain stability and the essential structural elements. Gly-rich linkers have been proven useful for these types of unstable interactions, particularly where the interaction is weak and transient, by creating a covalent link between the proteins to form a stable protein-protein complex. Gly-rich linkers are also employed to form stable covalently linked dimers, and to connect two independent domains that create a ligand-binding site or recognition sequence. The lengths of linkers vary from 2 to 31 amino acids, optimized for each condition so that the linker does not impose any constraints on the conformation or interactions of the linked partners. Various structures of covalently linked protein complexes have been described using X-ray crystallography, nuclear magnetic resonance and cryo-electron microscopy techniques. In this review, we evaluate several structural studies where linkers have been used to improve protein quality, to produce stable protein-protein complexes, and to obtain protein dimers.
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66
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Wang JH, Reinherz EL. The structural basis of αβ T-lineage immune recognition: TCR docking topologies, mechanotransduction, and co-receptor function. Immunol Rev 2012; 250:102-19. [PMID: 23046125 PMCID: PMC3694212 DOI: 10.1111/j.1600-065x.2012.01161.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Self versus non-self discrimination is at the core of T-lymphocyte recognition. To this end, αβ T-cell receptors (TCRs) ligate 'foreign' peptides bound to major histocompatibility complex (MHC) class I or class II molecules (pMHC) arrayed on the surface of antigen-presenting cells (APCs). Since the discovery of TCRs approximately 30 years ago, considerable structural and functional data have detailed the molecular basis of their extraordinary ligand specificity and sensitivity in mediating adaptive T-cell immunity. This review focuses on the structural biology of the Fab-like TCRαβ clonotypic heterodimer and its unique features in conjunction with those of the associated CD3εγ and CD3εδ heterodimeric molecules, which, along with CD3ζζ homodimer, comprise the TCR complex in a stoichiometry of 1:1:1:1. The basis of optimized TCRαβ docking geometry on the pMHC linked to TCR mechanotransduction and required for T-cell signaling as well as CD4 and CD8 co-receptor function is detailed. A model of the TCR ectodomain complex including its connecting peptides suggests how force generated during T-cell immune surveillance and at the immunological synapse results in dynamic TCR quaternary change involving its heterodimeric components. Potential insights from the structural biology relevant to immunity and immunosuppression are revealed.
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MESH Headings
- Animals
- Antigen-Presenting Cells/cytology
- Antigen-Presenting Cells/immunology
- Antigen-Presenting Cells/metabolism
- Antigens/chemistry
- Antigens/immunology
- Antigens/metabolism
- CD3 Complex/chemistry
- CD3 Complex/immunology
- CD3 Complex/metabolism
- CD4-Positive T-Lymphocytes/cytology
- CD4-Positive T-Lymphocytes/immunology
- CD4-Positive T-Lymphocytes/metabolism
- CD8-Positive T-Lymphocytes/cytology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- Humans
- Major Histocompatibility Complex/immunology
- Mechanotransduction, Cellular
- Mice
- Models, Molecular
- Peptides/chemistry
- Peptides/immunology
- Peptides/metabolism
- Protein Conformation
- Protein Multimerization
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
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Affiliation(s)
- Jia-huai Wang
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Ellis L. Reinherz
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Medicine, Harvard Medical School, Boston, MA, USA
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67
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Garcia KC. Reconciling views on T cell receptor germline bias for MHC. Trends Immunol 2012; 33:429-36. [PMID: 22771140 PMCID: PMC3983780 DOI: 10.1016/j.it.2012.05.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 05/13/2012] [Accepted: 05/13/2012] [Indexed: 01/25/2023]
Abstract
Whether MHC restriction by the T cell receptor (TCR) is a product of evolutionary pressures leading to germline-encoded 'rules of engagement' remains avidly debated. Structural results derived from analysis of TCR-peptide-MHC complexes appear to support a model of physical specificity between TCR germline V regions and MHC. Yet, some recent evidence suggests that thymic selection, and co-receptors may have misled us into thinking the TCR is exclusively MHC-specific, when in fact, TCRs can robustly engage non-MHC ligands when given the chance. Here, I propose that seemingly contradictory data and hypotheses for, and against, germline bias are, in fact, compatible and can be reconciled into a unifying model.
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Affiliation(s)
- K Christopher Garcia
- Howard Hughes Medical Institute, Department of Molecular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Knapp B, Fischer G, Van Hemelen D, Fae I, Maillere B, Ebner C, Schreiner W, Bohle B, Jahn-Schmid B. Association of HLA-DR1 with the allergic response to the major mugwort pollen allergen: molecular background. BMC Immunol 2012; 13:43. [PMID: 22871092 PMCID: PMC3522052 DOI: 10.1186/1471-2172-13-43] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 08/02/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mugwort pollen allergens represent the main cause of pollinosis in late summer. The major allergen, Art v 1, contains only one single immunodominant, solely HLA-DR-restricted T cell epitope (Art v 125-36). The frequency of HLA-DRB1*01 is highly increased in mugwort-allergic individuals and HLA-DR1 serves as restriction element for Art v 125-36. However, Art v 125-36 also binds to HLA-DR4 with high affinity and DR1-restricted Art v 125-36 -specific T cell receptors can be activated by HLA-DR4 molecules. To understand the predominance of HLA-DR1 in mugwort allergy in spite of the degeneracy in HLA/peptide-binding and TCR-recognition, we investigated the molecular background of Art v 125-36 /MHC/TCR interactions in the context of HLA-DR1 compared to -DR4. RESULTS The majority of Art v 125-36 -specific T cell lines and clones from HLA-DR1 carrying, mugwort pollen-allergic donors reacted to synthetic and naturally processed Art v 1-peptides when presented by HLA-DR1 or HLA-DR4 expressing antigen presenting cells. However, at limiting peptide concentrations DR1 was more effective in T cell stimulation. In addition, the minimal epitope for 50% of Art v 125-36 -specific T cells was shorter for DR1 than for DR4. In vitro binding assays of Art v 125-36 mutant peptides to isolated DR1- and DR4-molecules indicated similar binding capacities and use of the same register. In silico simulation of Art v 125-36 binding to HLA-DR1 and -DR4 suggested similar binding of the central part of the peptide to either molecule, but a higher flexibility of the N- and C-terminal amino acids and detachment at the C-terminus in HLA-DR1. CONCLUSIONS The predominance of HLA-DR1 in the response to Art v 125-36 may be explained by subtle conformation changes of the peptide bound to DR1 compared to DR4. Computer simulation supported our experimental data by demonstrating differences in peptide mobility within the HLA-DR complex that may influence TCR-binding. We suggest that the minor differences observed in vitro may be more relevant in the microenvironment in vivo, so that only presentation by HLA-DR1, but not -DR4 permits successful T cell activation.
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Affiliation(s)
- Bernhard Knapp
- Department for Biomedical Computersimulation and Bioinformatics, Medical University of Vienna, Vienna, Austria
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69
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Manikwar P, Kiptoo P, Badawi AH, Büyüktimkin B, Siahaan TJ. Antigen-specific blocking of CD4-specific immunological synapse formation using BPI and current therapies for autoimmune diseases. Med Res Rev 2012; 32:727-64. [PMID: 21433035 PMCID: PMC4441537 DOI: 10.1002/med.20243] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In this review, we discuss T-cell activation, etiology, and the current therapies of autoimmune diseases (i.e., MS, T1D, and RA). T-cells are activated upon interaction with antigen-presenting cells (APC) followed by a "bull's eye"-like formation of the immunological synapse (IS) at the T-cell-APC interface. Although the various disease-modifying therapies developed so far have been shown to modulate the IS and thus help in the management of these diseases, they are also known to present some undesirable side effects. In this study, we describe a novel and selective way to suppress autoimmunity by using a bifunctional peptide inhibitor (BPI). BPI uses an intercellular adhesion molecule-1 (ICAM-1)-binding peptide to target antigenic peptides (e.g., proteolipid peptide, glutamic acid decarboxylase, and type II collagen) to the APC and therefore modulate the immune response. The central hypothesis is that BPI blocks the IS formation by simultaneously binding to major histocompatibility complex-II and ICAM-1 on the APC and selectively alters the activation of T cells from T(H)1 to T(reg) and/or T(H)2 phenotypes, leading to tolerance.
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Affiliation(s)
- Prakash Manikwar
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KA 66047, USA
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70
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Huseby ES, Stadinski BD, Trenh P, Stern LJ. Response to Garcia et al. Immunity 2012; 36:889-90. [PMID: 22705102 DOI: 10.1016/j.immuni.2012.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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71
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Garcia KC, Gapin L, Adams JJ, Birnbaum ME, Scott-Browne JP, Kappler JW, Marrack P. A closer look at TCR germline recognition. Immunity 2012; 36:887-8. [PMID: 22705103 DOI: 10.1016/j.immuni.2012.05.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Indexed: 10/28/2022]
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72
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Kim ST, Shin Y, Brazin K, Mallis RJ, Sun ZYJ, Wagner G, Lang MJ, Reinherz EL. TCR Mechanobiology: Torques and Tunable Structures Linked to Early T Cell Signaling. Front Immunol 2012; 3:76. [PMID: 22566957 PMCID: PMC3342345 DOI: 10.3389/fimmu.2012.00076] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 03/27/2012] [Indexed: 11/16/2022] Open
Abstract
Mechanotransduction is a basis for receptor signaling in many biological systems. Recent data based upon optical tweezer experiments suggest that the TCR is an anisotropic mechanosensor, converting mechanical energy into biochemical signals upon specific peptide-MHC complex (pMHC) ligation. Tangential force applied along the pseudo-twofold symmetry axis of the TCR complex post-ligation results in the αβ heterodimer exerting torque on the CD3 heterodimers as a consequence of molecular movement at the T cell-APC interface. Accompanying TCR quaternary change likely fosters signaling via the lipid bilayer predicated on the magnitude and direction of the TCR-pMHC force. TCR glycans may modulate quaternary change, thereby altering signaling outcome as might the redox state of the CxxC motifs located proximal to the TM segments in the heterodimeric CD3 subunits. Predicted alterations in TCR TM segments and surrounding lipid will convert ectodomain ligation into the earliest intracellular signaling events.
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Affiliation(s)
- Sun Taek Kim
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical SchoolBoston, MA, USA
- Department of Medicine, Harvard Medical SchoolBoston, MA, USA
| | - Yongdae Shin
- Department of Mechanical Engineering, Massachusetts Institute of Technology, CambridgeMA, USA
| | - Kristine Brazin
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical SchoolBoston, MA, USA
- Department of Medicine, Harvard Medical SchoolBoston, MA, USA
| | - Robert J. Mallis
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical SchoolBoston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical SchoolBoston, MA, USA
| | - Zhen-Yu J. Sun
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical SchoolBoston, MA, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical SchoolBoston, MA, USA
| | - Matthew J. Lang
- Department of Chemical and Biomolecular Engineering, Vanderbilt UniversityNashville, TN, USA
| | - Ellis L. Reinherz
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical SchoolBoston, MA, USA
- Department of Medicine, Harvard Medical SchoolBoston, MA, USA
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73
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Castro R, Bernard D, Lefranc MP, Six A, Benmansour A, Boudinot P. T cell diversity and TcR repertoires in teleost fish. FISH & SHELLFISH IMMUNOLOGY 2011; 31:644-654. [PMID: 20804845 DOI: 10.1016/j.fsi.2010.08.016] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 08/17/2010] [Accepted: 08/22/2010] [Indexed: 05/29/2023]
Abstract
In vertebrates, the diverse and extended range of antigenic motifs is matched to large populations of lymphocytes. The concept of immune repertoire was proposed to describe this diversity of lymphocyte receptors--IG and TR--required for the recognition specificity. Immune repertoires have become useful tools to describe lymphocyte and receptor populations during the immune system development and in pathological situations. In teleosts, the presence of conventional T cells was first proposed to explain graft rejection and optimized specific antibody production. The discovery of TR genes definitely established the reality of conventional T cells in fish. The development of genomic and EST databases recently led to the description of several key T cell markers including CD4, CD8, CD3, CD28, CTLA4, as well as important cytokines, suggesting the existence of different T helper (Th) subtypes, similar to the mammalian Th1, Th2 and Th17. Over the last decade, repertoire studies have demonstrated that both public and private responses occur in fish as they do in mammals, and in vitro specific cytotoxicity assays have been established. While such typical features of T cells are similar in both fish and mammals, the structure of particular repertoires such as the one of gut intra-epithelial lymphocytes seems to be very different. Future studies will further reveal the particular characteristics of teleost T cell repertoires and adaptive responses.
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Affiliation(s)
- R Castro
- Virologie et Immunologie Moléculaires, INRA, 78352 Jouy-en-Josas, France
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74
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Matsutani T, Fujii Y, Kitaura K, Suzuki S, Tsuruta Y, Takasaki T, Ogasawara K, Nishimoto N, Kurane I, Suzuki R. Increased positive selection pressure within the complementarity determining regions of the T-cell receptor β gene in New World monkeys. Am J Primatol 2011; 73:1082-92. [PMID: 21769905 DOI: 10.1002/ajp.20976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 05/26/2011] [Accepted: 06/04/2011] [Indexed: 11/06/2022]
Abstract
Because of the long-term co-evolution of TCR and MHC molecules, numerous nucleotide substitutions have accumulated within the domains of TCRβ genes. We previously found that nonsynonymous nucleotide substitutions occurred more frequently in complementarity determining region (CDR)β than in CDRα, even though only a limited number of common marmoset (Callithrix jacchus) and human T-cell receptor β variable (TRBV) sequences were compared. This interesting finding raised the question of whether the increased selective pressure within CDRβ was species-specific. In this study, we identified 21 TRBV region sequences from the common marmoset and performed comparative sequence analyses of the T-cell receptor α variable (TRAV) and TRBV regions from human, chimpanzee, rhesus monkey, cotton-top tamarin, Ma's night monkey, and common marmoset. The ratios of the number of nonsynonymous nucleotide substitutions per site (d(N) ) to the d(S) values (d(N) /d(S) ) were less than 1 within the framework regions (FRs) of TRAV and TRBV region sequences, suggesting that purifying selection is largely dominant within the FRs. In contrast, the d(N) values were statistically significantly greater for CDRβ than for CDRα only in New World monkeys. Also, increased d(N) /d(S) ratios (d(N) /d(S) >1) were observed within CDRβ between humans and New World monkeys and, interestingly, between New World monkeys, which share a relatively recent common ancestor. Moreover, phylogenetic analysis by maximum likelihood analysis provided firm evidence to support that positive selection occurred within CDRβ along New World monkey lineages. These results suggest that increased positive selection pressure within CDRβ is common in New World monkeys rather than being species-specific. This study provides an intriguing insight into the co-evolution of TCR and MHC molecules within primates.
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Affiliation(s)
- Takaji Matsutani
- Laboratory of Immune Regulation, Wakayama Medical University, Osaka, Japan
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75
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Rowe CL, Matsuura H, Jardetzky TS, Longnecker R. Investigation of the function of the putative self-association site of Epstein-Barr virus (EBV) glycoprotein 42 (gp42). Virology 2011; 415:122-31. [PMID: 21550622 DOI: 10.1016/j.virol.2011.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Revised: 03/01/2011] [Accepted: 04/07/2011] [Indexed: 10/18/2022]
Abstract
The Epstein-Barr virus (EBV) glycoprotein 42 (gp42) is a type II membrane protein essential for entry into B cells but inhibits entry into epithelial cells. X-ray crystallography suggests that gp42 may form dimers when bound to human leukocyte antigen (HLA) class II receptor (Mullen et al., 2002) or multimerize when not bound to HLA class II (Kirschner et al., 2009). We investigated this self-association of gp42 using several different approaches. We generated soluble mutants of gp42 containing mutations within the self-association site and found that these mutants have a defect in fusion. The gp42 mutants bound to gH/gL and HLA class II, but were unable to bind wild-type gp42 or a cleavage mutant of gp42. Using purified gp42, gH/gL, and HLA, we found these proteins associate 1:1:1 by gel filtration suggesting that gp42 dimerization or multimerization does not occur or is a transient event undetectable by our methods.
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Affiliation(s)
- Cynthia L Rowe
- Department of Microbiology and Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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76
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Patarroyo ME, Bermúdez A, Patarroyo MA. Structural and Immunological Principles Leading to Chemically Synthesized, Multiantigenic, Multistage, Minimal Subunit-Based Vaccine Development. Chem Rev 2011; 111:3459-507. [DOI: 10.1021/cr100223m] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Manuel Elkin Patarroyo
- Fundación Instituto de Inmunología de Colombia (FIDIC), Carrera 50, No. 26-00, Bogotá, Colombia
- Universidad Nacional de Colombia
| | - Adriana Bermúdez
- Fundación Instituto de Inmunología de Colombia (FIDIC), Carrera 50, No. 26-00, Bogotá, Colombia
- Universidad del Rosario
| | - Manuel Alfonso Patarroyo
- Fundación Instituto de Inmunología de Colombia (FIDIC), Carrera 50, No. 26-00, Bogotá, Colombia
- Universidad del Rosario
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77
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Khan JM, Ranganathan S. Understanding TR binding to pMHC complexes: how does a TR scan many pMHC complexes yet preferentially bind to one. PLoS One 2011; 6:e17194. [PMID: 21364947 PMCID: PMC3043089 DOI: 10.1371/journal.pone.0017194] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 01/22/2011] [Indexed: 01/08/2023] Open
Abstract
Understanding the basis of the binding of a T cell receptor (TR) to the peptide-MHC (pMHC) complex is essential due to the vital role it plays in adaptive immune response. We describe the use of computed binding (free) energy (BE), TR paratope, pMHC epitope, molecular surface electrostatic potential (MSEP) and calculated TR docking angle (θ) to analyse 61 TR/pMHC crystallographic structures to comprehend TR/pMHC interaction. In doing so, we have successfully demonstrated a novel/rational approach for θ calculation, obtained a linear correlation between BE and θ without any “codon” or amino acid preference, provided an explanation for TR ability to scan many pMHC ligands yet specifically bind one, proposed a mechanism for pMHC recognition by TR leading to T cell activation and illustrated the importance of the peptide in determining TR specificity, challenging the “germline bias” theory.
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MESH Headings
- Animals
- Comprehension/physiology
- Energy Metabolism/physiology
- Histocompatibility Antigens Class I/chemistry
- Histocompatibility Antigens Class I/immunology
- Histocompatibility Antigens Class I/metabolism
- Humans
- Lymphocyte Activation/immunology
- Mice
- Models, Biological
- Models, Molecular
- Multiprotein Complexes/chemistry
- Multiprotein Complexes/immunology
- Multiprotein Complexes/metabolism
- Protein Binding/physiology
- Protein Structure, Quaternary
- Protein Structure, Secondary
- Receptors, Antigen, T-Cell/agonists
- Receptors, Antigen, T-Cell/chemistry
- Receptors, Antigen, T-Cell/immunology
- Receptors, Antigen, T-Cell/metabolism
- Substrate Specificity/immunology
- T-Cell Antigen Receptor Specificity/immunology
- T-Cell Antigen Receptor Specificity/physiology
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Affiliation(s)
- Javed Mohammed Khan
- Department of Chemistry and Biomolecular Sciences and ARC Centre of Excellence in Bioinformatics, Macquarie University, Sydney, Australia
| | - Shoba Ranganathan
- Department of Chemistry and Biomolecular Sciences and ARC Centre of Excellence in Bioinformatics, Macquarie University, Sydney, Australia
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- * E-mail:
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78
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Yin Y, Li Y, Kerzic MC, Martin R, Mariuzza RA. Structure of a TCR with high affinity for self-antigen reveals basis for escape from negative selection. EMBO J 2011; 30:1137-48. [PMID: 21297580 DOI: 10.1038/emboj.2011.21] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Accepted: 01/10/2011] [Indexed: 11/10/2022] Open
Abstract
The failure to eliminate self-reactive T cells during negative selection is a prerequisite for autoimmunity. To escape deletion, autoreactive T-cell receptors (TCRs) may form unstable complexes with self-peptide-MHC by adopting suboptimal binding topologies compared with anti-microbial TCRs. Alternatively, escape can occur by weak binding between self-peptides and MHC. We determined the structure of a human autoimmune TCR (MS2-3C8) bound to a self-peptide from myelin basic protein (MBP) and the multiple sclerosis-associated MHC molecule HLA-DR4. MBP is loosely accommodated in the HLA-DR4-binding groove, accounting for its low affinity. Conversely, MS2-3C8 binds MBP-DR4 as tightly as the most avid anti-microbial TCRs. MS2-3C8 engages self-antigen via a docking mode that resembles the optimal topology of anti-foreign TCRs, but is distinct from that of other autoreactive TCRs. Combined with a unique CDR3β conformation, this docking mode compensates for the weak binding of MBP to HLA-DR4 by maximizing interactions between MS2-3C8 and MBP. Thus, the MS2-3C8-MBP-DR4 complex reveals the basis for an alternative strategy whereby autoreactive T cells escape negative selection, yet retain the ability to initiate autoimmunity.
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Affiliation(s)
- Yiyuan Yin
- Institute for Bioscience and Biotechnology Research, University of Maryland, WM Keck Laboratory for Structural Biology, Rockville, MD, USA
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79
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Sethi DK, Schubert DA, Anders AK, Heroux A, Bonsor DA, Thomas CP, Sundberg EJ, Pyrdol J, Wucherpfennig KW. A highly tilted binding mode by a self-reactive T cell receptor results in altered engagement of peptide and MHC. ACTA ACUST UNITED AC 2011; 208:91-102. [PMID: 21199956 PMCID: PMC3023130 DOI: 10.1084/jem.20100725] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A TCR derived from a patient with relapsing-remitting multiple sclerosis engages the self-peptide myelin basic protein in the context of HLA-DQ1 in a very unusual way. Self-reactive T cells that escape elimination in the thymus can cause autoimmune pathology, and it is therefore important to understand the structural mechanisms of self-antigen recognition. We report the crystal structure of a T cell receptor (TCR) from a patient with relapsing-remitting multiple sclerosis that engages its self-peptide–major histocompatibility complex (pMHC) ligand in an unusual manner. The TCR is bound in a highly tilted orientation that prevents interaction of the TCR-α chain with the MHC class II β chain helix. In this structure, only a single germline-encoded TCR loop engages the MHC protein, whereas in most other TCR-pMHC structures all four germline-encoded TCR loops bind to the MHC helices. The tilted binding mode also prevents peptide contacts by the short complementarity-determining region (CDR) 3β loop, and interactions that contribute to peptide side chain specificity are focused on the CDR3α loop. This structure is the first example in which only a single germline-encoded TCR loop contacts the MHC helices. Furthermore, the reduced interaction surface with the peptide may facilitate TCR cross-reactivity. The structural alterations in the trimolecular complex are distinct from previously characterized self-reactive TCRs, indicating that there are multiple unusual ways for self-reactive TCRs to bind their pMHC ligand.
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Affiliation(s)
- Dhruv K Sethi
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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80
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Bidirectional binding of invariant chain peptides to an MHC class II molecule. Proc Natl Acad Sci U S A 2010; 107:22219-24. [PMID: 21115828 DOI: 10.1073/pnas.1014708107] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
T-cell recognition of peptides bound to MHC class II (MHCII) molecules is a central event in cell-mediated adaptive immunity. The current paradigm holds that prebound class II-associated invariant chain peptides (CLIP) and all subsequent antigens maintain a canonical orientation in the MHCII binding groove. Here we provide evidence for MHCII-bound CLIP inversion. NMR spectroscopy demonstrates that the interconversion from the canonical to the inverse alignment is a dynamic process, and X-ray crystallography shows that conserved MHC residues form a hydrogen bond network with the peptide backbone in both orientations. The natural catalyst HLA-DM accelerates peptide reorientation and the exchange of either canonically or inversely bound CLIP against antigenic peptide. Thus, noncanonical MHC-CLIP displays the hallmarks of a structurally and functionally intact antigen-presenting complex.
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81
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Wucherpfennig KW. The First Structures of T Cell Receptors Bound to Peptide–MHC. THE JOURNAL OF IMMUNOLOGY 2010; 185:6391-3. [DOI: 10.4049/jimmunol.1090110] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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82
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Kim CH, Oh K, Kim DE, Lee SB, Yang JH, Lee G, Cho J, Lee DS. Both CD45RA+ and CD45RO+ human CD4+ T cells drive direct xenogeneic T-cell responses against porcine aortic endothelial cells. Xenotransplantation 2010; 17:224-32. [PMID: 20636543 DOI: 10.1111/j.1399-3089.2010.00582.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Xenogeneic cellular immune responses are mediated by either direct or indirect pathways depending on the participation of donor or host antigen presenting cells, respectively. The contribution of direct response of human T cells, especially memory T cells, to porcine antigen presenting cells is currently unknown. Here, we sought to determine whether human peripheral blood memory/activated phenotype T cells are directly responsive to porcine endothelial cells. METHODS Porcine aortic endothelial cells (PAECs) were prepared from Yorkshire or miniature pigs. Highly purified human T cells, including naïve and memory/activated phenotype cells, were incubated with PAECs with or without the addition of exogenous cytokines. T-cell proliferation and T-cell receptor (TCR) Vbeta usage in response to PAECs were analyzed. RESULTS Both CD8(+) and CD4(+) T cells responded directly to PAECs and exhibited exclusive responsiveness to SLA class I and class II molecules, respectively. Naïve and memory/activated phenotype CD4(+) T cells responded against PAECs, whereas only naïve phenotype CD8(+) T cells contributed to such a response. In addition, both populations of xenogeneic human CD4(+) T cells exhibited similar and diverse V beta usage. CONCLUSION Due to the considerable contribution of human CD45RO(+)CD4(+) T cells to the xenoreactivity against PAECs, effective control of xenogeneic memory/activated T-cell responses would significantly affect long-term survival of transplanted grafts.
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Affiliation(s)
- Chi Hwa Kim
- Laboratory of Immunology, Department of Anatomy, College of Medicine, Seoul National University, Seoul, Korea
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83
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Wang H, Fang Z, Morita CT. Vgamma2Vdelta2 T Cell Receptor recognition of prenyl pyrophosphates is dependent on all CDRs. THE JOURNAL OF IMMUNOLOGY 2010; 184:6209-22. [PMID: 20483784 DOI: 10.4049/jimmunol.1000231] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
gammadelta T cells differ from alphabeta T cells in the Ags they recognize and their functions in immunity. Although most alphabeta TCRs recognize peptides presented by MHC class I or II, human gammadelta T cells expressing Vgamma2Vdelta2 TCRs recognize nonpeptide prenyl pyrophosphates. To define the molecular basis for this recognition, the effect of mutations in the TCR CDR was assessed. Mutations in all CDR loops altered recognition and cover a large footprint. Unlike murine gammadelta TCR recognition of the MHC class Ib T22 protein, there was no CDR3delta motif required for recognition because only one residue is required. Instead, the length and sequence of CDR3gamma was key. Although a prenyl pyrophosphate-binding site was defined by Lys109 in Jgamma1.2 and Arg51 in CDR2delta, the area outlined by critical mutations is much larger. These results show that prenyl pyrophosphate recognition is primarily by germline-encoded regions of the gammadelta TCR, allowing a high proportion of Vgamma2Vdelta2 TCRs to respond. This underscores its parallels to innate immune receptors. Our results also provide strong evidence for the existence of an Ag-presenting molecule for prenyl pyrophosphates.
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Affiliation(s)
- Hong Wang
- Division of Rheumatology, Department of Internal Medicine, Interdisciplinary Graduate Program in Immunology, University of Iowa College of Medicine, Iowa City, IA 52242, USA
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84
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Liu L, Li Z, Guo Y, VanVranken SJ, Mourad W, Li H. Crystal structure of the Mycoplasma arthritidis-derived mitogen in apo form reveals a 3D domain-swapped dimer. J Mol Biol 2010; 399:367-76. [PMID: 20417218 DOI: 10.1016/j.jmb.2010.04.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 03/12/2010] [Accepted: 04/16/2010] [Indexed: 10/19/2022]
Abstract
Mycoplasma arthritidis-derived mitogen (MAM) is a superantigen that can activate large fractions of T cells bearing particular Vbeta elements of T cell receptor. Here, we report the crystal structure of a MAM mutant K201A in apo form (unliganded) at 2.8-A resolutions. We also partially refined the crystal structures of the MAM wild type and another MAM mutant L50A in apo forms at low resolutions. Unexpectedly, the structures of these apo MAM molecules display a three-dimensional domain-swapped dimer. The entire C-terminal domains of these MAM molecules are involved in the domain swapping. Functional analyses demonstrated that the K201A and L50A mutants do not show altered ability to bind to their host receptors and that they stimulate the activation of T cells as efficiently as does the wild type. Structural comparisons indicated that the "reconstituted" MAM monomer from the domain-swapped dimer displays large differences at the hinge regions from the MAM(wt) molecule in the receptor-bound form. Further comparison indicated that MAM has a flexible N-terminal loop, implying that conformational changes could occur upon receptor binding.
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Affiliation(s)
- Lihui Liu
- Wadsworth Center, New York State Department of Health, 120 New Scotland Ave, Albany, NY 12208, USA
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85
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Comprehensive analysis and characterization of the TCR α chain sequences in the common marmoset. Immunogenetics 2010; 62:383-95. [DOI: 10.1007/s00251-010-0445-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 03/26/2010] [Indexed: 11/27/2022]
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86
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Yoshida K, Corper AL, Herro R, Jabri B, Wilson IA, Teyton L. The diabetogenic mouse MHC class II molecule I-Ag7 is endowed with a switch that modulates TCR affinity. J Clin Invest 2010; 120:1578-90. [PMID: 20407212 DOI: 10.1172/jci41502] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Accepted: 02/03/2010] [Indexed: 11/17/2022] Open
Abstract
Genetic susceptibility to autoimmunity is frequently associated with specific MHC alleles. Diabetogenic MHC class II molecules, such as human HLA-DQ8 and mouse I-Ag7, typically have a small, uncharged amino acid residue at position 57 of their beta chain (beta57); this results in the absence of a salt bridge between beta57 and Argalpha76, which is adjacent to the P9 pocket of the peptide-binding groove. However, the influence of Argalpha76 on the selection of the TCR repertoire remains unknown, particularly when the MHC molecule binds a peptide with a neutral amino acid residue at position P9. Here, we have shown that diabetogenic MHC class II molecules bound to a peptide with a neutral P9 residue primarily selected and expanded cells expressing TCRs bearing a negatively charged residue in the first segment of their complementarity determining region 3beta. The crystal structure of one such TCR in complex with I-Ag7 bound to a peptide containing a neutral P9 residue revealed that a network of favorable long-range (greater than 4 A) electrostatic interactions existed among Argalpha76, the neutral P9 residue, and TCR, which supported the substantially increased TCR/peptide-MHC affinity. This network could be modulated or switched to a lower affinity interaction by the introduction of a negative charge at position P9 of the peptide. Our results support the existence of a switch at residue beta57 of the I-Ag7 and HLA-DQ8 class II molecules and potentially link normal thymic TCR selection with abnormal peripheral behavior.
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Affiliation(s)
- Kenji Yoshida
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037, USA
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87
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Patarroyo MA, Bermúdez A, López C, Yepes G, Patarroyo ME. 3D analysis of the TCR/pMHCII complex formation in monkeys vaccinated with the first peptide inducing sterilizing immunity against human malaria. PLoS One 2010; 5:e9771. [PMID: 20333301 PMCID: PMC2841639 DOI: 10.1371/journal.pone.0009771] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Accepted: 02/25/2010] [Indexed: 11/18/2022] Open
Abstract
T-cell receptor gene rearrangements were studied in Aotus monkeys developing high antibody titers and sterilizing immunity against the Plasmodium falciparum malaria parasite upon vaccination with the modified synthetic peptide 24112, which was identified in the Merozoite Surface Protein 2 (MSP-2) and is known to bind to HLA-DRβ1*0403 molecules with high capacity. Spectratyping analysis showed a preferential usage of Vβ12 and Vβ6 TCR gene families in 67% of HLA-DRβ1*0403-like genotyped monkeys. Docking of peptide 24112 into the HLA-DRβ1*0401–HA peptide–HA1.7TCR complex containing the VDJ rearrangements identified in fully protected monkeys showed a different structural signature compared to nonprotected monkeys. These striking results show the exquisite specificity of the TCR/pMHCII complex formation needed for inducing sterilizing immunity and provide important hints for a logical and rational methodology to develop multiepitopic, minimal subunit-based synthetic vaccines against infectious diseases, among them malaria.
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Affiliation(s)
- Manuel A. Patarroyo
- Fundación Instituto de Inmunología de Colombia, Bogotá, Cundinamarca, Colombia
- Universidad del Rosario, Bogotá, Cundinamarca, Colombia
| | - Adriana Bermúdez
- Fundación Instituto de Inmunología de Colombia, Bogotá, Cundinamarca, Colombia
- Universidad del Rosario, Bogotá, Cundinamarca, Colombia
| | - Carolina López
- Fundación Instituto de Inmunología de Colombia, Bogotá, Cundinamarca, Colombia
- Universidad del Rosario, Bogotá, Cundinamarca, Colombia
| | - Gloria Yepes
- Fundación Instituto de Inmunología de Colombia, Bogotá, Cundinamarca, Colombia
| | - Manuel E. Patarroyo
- Fundación Instituto de Inmunología de Colombia, Bogotá, Cundinamarca, Colombia
- Universidad Nacional de Colombia, Bogotá, Cundinamarca, Colombia
- * E-mail:
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88
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Structural biology of the T-cell receptor: insights into receptor assembly, ligand recognition, and initiation of signaling. Cold Spring Harb Perspect Biol 2010; 2:a005140. [PMID: 20452950 DOI: 10.1101/cshperspect.a005140] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The T-cell receptor (TCR)-CD3 complex serves as a central paradigm for general principles of receptor assembly, ligand recognition, and signaling in the immune system. There is no other receptor system that matches the diversity of both receptor and ligand components. The recent expansion of the immunological structural database is beginning to identify key principles of MHC and peptide recognition. The multicomponent assembly of the TCR complex illustrates general principles used by many receptors in the immune system, which rely on basic and acidic transmembrane residues to guide assembly. The intrinsic binding of the cytoplasmic domains of the CD3epsilon and zeta chains to the inner leaflet of the plasma membrane represents a novel mechanism for control of receptor activation: Insertion of critical CD3epsilon tyrosines into the hydrophobic membrane core prevents their phosphorylation before receptor engagement.
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89
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Abstract
T cell activation begins with the interaction between an antigen-specific T cell and an antigen-presenting cell (APC). This interaction results in the formation of the immunological synapse, which had been considered to be responsible for antigen recognition and T cell activation. Recent advances in imaging analysis have provided new insights into T cell activation. The T cell receptor (TCR) microclusters, TCRs, kinases, and adaptors are generated upon antigen recognition at the interfaces between the T cells and the APCs and serve as a fundamental signaling unit for T cell activation. CD28-mediated costimulation is also found to be regulated by the formation of microclusters. Therefore, the dynamic regulations of TCR and CD28 microcluster formation, migration, and interaction are the key events for the initiation of T cell-mediated immune responses. Comprehensive analyses of the composition and characteristics of the TCR microcluster have identified its dynamic features. This review will outline new discoveries of the microclusters and its related concept in T cell activation.
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90
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van Boxel GI, Stewart-Jones G, Holmes S, Sainsbury S, Shepherd D, Gillespie GMA, Harlos K, Stuart DI, Owens R, Jones EY. Some lessons from the systematic production and structural analysis of soluble (alpha)(beta) T-cell receptors. J Immunol Methods 2009; 350:14-21. [PMID: 19715696 DOI: 10.1016/j.jim.2009.08.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 07/29/2009] [Accepted: 08/17/2009] [Indexed: 01/20/2023]
Abstract
T-cell receptors (TCRs) are membrane proteins which recognize antigens with high specificity forming the basis of the cellular immune response. The study of these receptors has been limited by the challenges in expressing sufficient quantities of stable soluble protein. Here we report our systematic approach for generating soluble, (alpha)(beta)-TCRs, for X-ray crystallographic studies. By using small-scale expression screens, novel standardized quality control mechanisms and crystallization and imaging robots we were able to add significantly to the current TCR structural database. Our success in crystallizing both isolated TCRs and Major histocompatibility complex (MHC):TCR complexes has provided us with sufficient data to develop focused crystallization screens, which have proved generically useful for the crystallization of this family of proteins and complexes.
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MESH Headings
- Animals
- Crystallography, X-Ray/methods
- Histocompatibility Antigens/chemistry
- Histocompatibility Antigens/immunology
- Histocompatibility Antigens/metabolism
- Humans
- Protein Structure, Quaternary/physiology
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Solubility
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Affiliation(s)
- Gijs I van Boxel
- Cancer Research UK Receptor Structure Research Group, Division of Structural Biology, The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Headington, Oxford OX3 7BN, UK
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91
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Wucherpfennig KW, Call MJ, Deng L, Mariuzza R. Structural alterations in peptide-MHC recognition by self-reactive T cell receptors. Curr Opin Immunol 2009; 21:590-5. [PMID: 19699075 DOI: 10.1016/j.coi.2009.07.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 07/08/2009] [Accepted: 07/10/2009] [Indexed: 10/20/2022]
Abstract
The crystal structures of five autoimmune T cell receptor (TCR)-peptide-MHC complexes reveal substantial structural alterations compared to antimicrobial TCRs. The two human TCRs bind their self-peptide-MHC ligands with an altered topology, while the three mouse receptors recognize a self-peptide that only partially fills the MHC-binding groove. In most cases the peptide is contacted only by a subset of available TCR complementarity-determining loops and there is a paucity of hydrogen bonds from TCR to peptide. These suboptimal binding properties may have enabled escape from negative thymic selection. While only minute amounts of antigen are typically available for negative selection, the antigens recognized by many autoimmune TCRs are abundant in the target organ. Such compensatory mechanisms can allow self-reactive T cells with altered TCR-binding properties to be pathogenic.
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Affiliation(s)
- Kai W Wucherpfennig
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
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92
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Collins EJ, Riddle DS. TCR-MHC docking orientation: natural selection, or thymic selection? Immunol Res 2009; 41:267-94. [PMID: 18726714 DOI: 10.1007/s12026-008-8040-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
T cell receptors (TCR) dock on their peptide-major histocompatibility complex (pMHC) targets in a conserved orientation. Since amino acid sidechains are the foundation of specific protein-protein interactions, a simple explanation for the conserved docking orientation is that key amino acids encoded by the TCR and MHC genes have been selected and maintained through evolution in order to preserve TCR/pMHC binding. Expectations that follow from the hypothesis that TCR and MHC evolved to interact are discussed in light of the data that both support and refute them. Finally, an alternative and equally simple explanation for the driving force behind the conserved docking orientation is described.
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Affiliation(s)
- Edward J Collins
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, 804 Mary Ellen Jones Building, Chapel Hill, NC 27510, USA.
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93
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Udyavar A, Alli R, Nguyen P, Baker L, Geiger TL. Subtle affinity-enhancing mutations in a myelin oligodendrocyte glycoprotein-specific TCR alter specificity and generate new self-reactivity. THE JOURNAL OF IMMUNOLOGY 2009; 182:4439-47. [PMID: 19299745 DOI: 10.4049/jimmunol.0804377] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We describe a simple iterative approach to augment TCR affinity, which we studied using a myelin oligodendrocyte glycoprotein-specific TCR. We hypothesized that single amino acid modifications in TCR CDR3 could enhance TCR sensitivity through focal interactions with antigenic peptide while minimizing the risk of cross-reactivity observed previously in TCR more broadly mutagenized using in vitro evolution techniques. We show that this iterative method can indeed generate TCR with Ag sensitivity 100-fold greater than the parental receptor and can endow TCR with coreceptor independence. However, we also find that single amino acid mutations in the CDR3 can alter TCR fine specificity, affecting recognition requirements for Ag residues over most of the length of the MHC binding groove. Furthermore, minimal changes in surface-exposed CDR3 amino acids, even the addition of a single hydroxyl group or conversion of a methyl or sulfhydryl moiety to a hydroxyl, can confer modified Ag-specific TCR with new self-reactivity. In vivo modeling of modified TCR through retroviral TCR gene transfer into Rag(-/-) mice confirmed the biological significance of these altered reactivities, although it also demonstrated the feasibility of producing Ag-specific, positively selecting, coreceptor-independent receptors with markedly increased Ag sensitivity. These results affirm the possibility of readily generating affinity-enhanced TCR for therapeutic purposes but demonstrate that minimal changes in TCR CDR3 structure can promote self reactivity and thereby emphasize the importance of caution in validating receptors with even subtle alterations before clinical application.
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Affiliation(s)
- Akshata Udyavar
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
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94
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Patarroyo ME, Cifuentes G, Bermúdez A, Patarroyo MA. Strategies for developing multi-epitope, subunit-based, chemically synthesized anti-malarial vaccines. J Cell Mol Med 2009; 12:1915-35. [PMID: 19012725 PMCID: PMC4506160 DOI: 10.1111/j.1582-4934.2008.00174.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
An anti-malarial vaccine against the extremely lethal Plasmodium falciparum is desperately needed. Peptides from this parasite's proteins involved in invasion and having high red blood cell-binding ability were identified; these conserved peptides were not immun genic or protection-inducing when used for immunizing Aotus monkeys. Modifying some critical binding residues in these high-activi binding peptides' (HABPs') attachment to red blood cells (RBC) allowed them to induce immunogenicity and protection against expermental challenge and acquire the ability to bind to specific HLA-DRp1* alleles. These modified HABPs adopted certain characterist structural configurations as determined by circular dichroism (CD) and 1H nuclear magnetic resonance (NMR) associated with certain HLA-DRβ1* haplotype binding activities and characteristics, such as a 2-Å-distance difference between amino acids fitting into HLA-DRp1 Pockets 1 to 9, residues participating in binding to HLA-DR pockets and residues making contact with the TCR, suggesting haplotyp and allele-conscious TCR. This has been demonstrated in HLA-DR-like genotyped monkeys and provides the basis for designing high effective, subunit-based, multi-antigen, multi-stage, synthetic vaccines, for immediate human use, malaria being one of them.
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Affiliation(s)
- M E Patarroyo
- Fundación Instituto de Inmunólogia de Colombia (FIDIC), Bogotá, Colombia.
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95
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Abstract
T-cell receptors (TCRs) are structurally related to antibodies, and also interact with a diverse set of ligands. TCRs recognize foreign peptide antigens displayed by major histocompatibility complex (MHC) molecules and foreign lipid-based antigens presented by CD1. These interactions initiate an immune response through T-cell activation. These critical surveillance and response initiation functions of the adaptive immune system are not perfect, though, as TCR interactions with self antigens can lead to autoimmune disease. Mutated peptides can also be recognized specifically by TCRs, and may be important in tumor immunity. TCRs are also bound specifically by a family of bacterial toxins called superantigens, which over-stimulate the immune system to cause numerous human diseases.
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Affiliation(s)
- Eric J Sundberg
- Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA
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96
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97
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Altered peptide ligands can modify the Th2 T cell response to the immunodominant 161-175 peptide of LACK (Leishmania homolog for the receptor of activated C kinase). Mol Immunol 2008; 46:366-74. [PMID: 19042022 DOI: 10.1016/j.molimm.2008.10.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Revised: 10/16/2008] [Accepted: 10/20/2008] [Indexed: 12/22/2022]
Abstract
Following Leishmania major infection, the early LACK (Leishmania homolog of receptors for activated C kinase)-induced IL-4 response appears to determine disease susceptibility in BALB/c mice. Therefore, we sought to manipulate the pathogenic T cell responses to the immunodominant epitope with the use of altered peptide ligands (APLs). Conservative and non-conservative substitutions for each amino acid of the LACK 161-175 peptide determinant were tested for their stimulatory capacity in four different LACK-reactive T cell systems. From these results, we propose a likely LACK 163-171/I-A(d) core peptide register and show that APLs with changes at putative T cell receptor (TCR) contacts provide the greatest potential for immune deviation. In particular, the TCR-contact H164V APL expanded Th1 cells upon in vitro recall of naïve splenocytes from LACK-specific BV4 T cell receptor transgenic mice and stimulated IFN-gamma secretion from a Th2-committed LACK-reactive T cell line. We also observed that non-conservative substitutions flanking the core determinant had strong agonistic effects for proliferation and Th1/Th2 modulation. However, upon immunization, the H164V APL considerably downregulated proliferation and cytokine responses to the wild type LACK 161-175 peptide, while immunization with the weak agonist, MHC contact APL S171K, increased the IFN-gamma/IL-4 ratio to the wild type peptide. In these instances, a hyporesponsive T cell response to the wild-type peptide was achieved by immunizing with an APL possessing non-conservative substitutions at TCR contact sites, while immune deviation was accomplished using a weak-agonist APL that retained the core determinant. Thus, certain LACK-APLs are able to induce T cell responses with a protective phenotype in an infectious disease such as leishmaniasis.
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98
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Armstrong K, Piepenbrink K, Baker B. Conformational changes and flexibility in T-cell receptor recognition of peptide-MHC complexes. Biochem J 2008; 415:183-96. [PMID: 18800968 PMCID: PMC2782316 DOI: 10.1042/bj20080850] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 06/23/2008] [Accepted: 07/09/2008] [Indexed: 01/07/2023]
Abstract
A necessary feature of the immune system, TCR (T-cell receptor) cross-reactivity has been implicated in numerous autoimmune pathologies and is an underlying cause of transplant rejection. Early studies of the interactions of alphabeta TCRs (T-cell receptors) with their peptide-MHC ligands suggested that conformational plasticity in the TCR CDR (complementarity determining region) loops is a dominant contributor to T-cell cross-reactivity. Since these initial studies, the database of TCRs whose structures have been solved both bound and free is now large enough to permit general conclusions to be drawn about the extent of TCR plasticity and the types and locations of motion that occur. In the present paper, we review the conformational differences between free and bound TCRs, quantifying the structural changes that occur and discussing their possible roles in specificity and cross-reactivity. We show that, rather than undergoing major structural alterations or 'folding' upon binding, the majority of TCR CDR loops shift by relatively small amounts. The structural changes that do occur are dominated by hinge-bending motions, with loop remodelling usually occurring near loop apexes. As predicted from previous studies, the largest changes are in the hypervariable CDR3alpha and CDR3beta loops, although in some cases the germline-encoded CDR1alpha and CDR2alpha loops shift in magnitudes that approximate those of the CDR3 loops. Intriguingly, the smallest shifts are in the germline-encoded loops of the beta-chain, consistent with recent suggestions that the TCR beta domain may drive ligand recognition.
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Affiliation(s)
- Kathryn M. Armstrong
- *Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, U.S.A
| | - Kurt H. Piepenbrink
- *Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, U.S.A
| | - Brian M. Baker
- *Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, U.S.A
- †Walther Cancer Research Center, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, U.S.A
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99
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Ma Z, Sharp KA, Janmey PA, Finkel TH. Surface-anchored monomeric agonist pMHCs alone trigger TCR with high sensitivity. PLoS Biol 2008; 6:e43. [PMID: 18303949 PMCID: PMC2253636 DOI: 10.1371/journal.pbio.0060043] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Accepted: 01/08/2008] [Indexed: 12/03/2022] Open
Abstract
At the interface between T cell and antigen-presenting cell (APC), peptide antigen presented by MHC (pMHC) binds to the T cell receptor (TCR) and initiates signaling. The mechanism of TCR signal initiation, or triggering, remains unclear. An interesting aspect of this puzzle is that although soluble agonist pMHCs cannot trigger TCR even at high concentrations, the same ligands trigger TCR very efficiently on the surface of APCs. Here, using lipid bilayers or plastic-based artificial APCs with defined components, we identify the critical APC-associated factors that confer agonist pMHCs with such potency. We found that CD4+ T cells are triggered by very low numbers of monomeric agonist pMHCs anchored on fluid lipid bilayers or fixed plastic surfaces, in the absence of any other APC surface molecules. Importantly, on bilayers, plastic surfaces, or real APCs, endogenous pMHCs did not enhance TCR triggering. TCR triggering, however, critically depended upon the adhesiveness of the surface and an intact T cell actin cytoskeleton. Based on these observations, we propose the receptor deformation model of TCR triggering to explain the remarkable sensitivity and specificity of TCR triggering. Using the T cell receptor (TCR) as a sensor, T cells of the immune system constantly migrate in lymphoid organs and probe the surface of antigen-presenting cells (APCs) for foreign antigens, a sign of pathogen infection. Antigen binding by TCRs leads to T cell activation and subsequent immune response to combat the pathogens. Interestingly, although T cells respond well to antigens on APCs, they do not recognize the same antigens in solution. What is it that makes antigens on APCs recognizable? To address this, we used lipid bilayers and plastic surfaces to construct artificial APCs with defined antigen number, composition, and configuration. We found that T cells respond to very few individual foreign antigens on artificial APCs, and contrary to some current opinion, formation of antigen clusters on APCs is not required for antigen recognition by T cells. TCR triggering, however, requires T cell adhesion to the APC surface and then occurs only if the T cells are able to move. We propose that at the dynamic T cell–APC interface, antigen on APCs activates T cells by applying force to the TCR and deforming its structure, which cannot be achieved by soluble antigens due to their lack of anchorage. Why is it that T cells are blind to antigens in solution but highly sensitive to antigens anchored on a surface? The authors show that this is not due to antigen clustering, but could involve mechanical forces associated with cell locomotion.
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Affiliation(s)
- Zhengyu Ma
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- * To whom correspondence should be addressed. E-mail: (ZM); (THF)
| | - Kim A Sharp
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Paul A Janmey
- Institute for Medicine and Engineering, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Terri H Finkel
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- * To whom correspondence should be addressed. E-mail: (ZM); (THF)
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100
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Marrack P, Scott-Browne JP, Dai S, Gapin L, Kappler JW. Evolutionarily conserved amino acids that control TCR-MHC interaction. Annu Rev Immunol 2008; 26:171-203. [PMID: 18304006 DOI: 10.1146/annurev.immunol.26.021607.090421] [Citation(s) in RCA: 206] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The rules for the conserved reaction of alphabeta T cell receptors (TCRs) with major histocompatibility complex (MHC) proteins plus peptides are poorly understood, probably because thymocytes bearing TCRs with the strongest MHC reactivity are lost by negative selection. Thus, only TCRs with an attenuated ability to react with MHC appear on mature T cells. Also, the interaction sites between TCRs and MHC may be inherently flexible and hence difficult to spot. We reevaluated contacts between TCRs and MHC in the solved structures of their complexes with these points in mind. Relatively conserved amino acids in the TCR complementarity-determining regions (CDR) 1 and CDR2 are often used to bind exposed areas of the MHC alpha-helices. These areas are exposed because of small amino acids that allow somewhat flexible binding of the TCRs. The TCR amino acids involved are specific to families of variable (V) regions and to some extent different rules may govern the recognition of MHCI versus MHCII.
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Affiliation(s)
- Philippa Marrack
- Howard Hughes Medical Institute, University of Colorado Denver Health Science Center, Denver, Colorado 80206, USA.
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