Protective role of major histocompatibility complex class II Ebd transgene on collagen-induced arthritis.
Miguel Á. González‐GayGerald NaboznyMarilyn J. BullEric ZanelliJohn DouhanMarie GriffithsL H GlimcherH. S. LuthraC S David
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Abstract:
Collagen-induced arthritis (CIA) is an animal model of autoimmune inflammatory polyarthritis that has features similar to rheumatoid arthritis (RA). Much like RA, susceptibility to mouse CIA is influenced by the major histocompatibility complex (MHC), H-2, and restricted to the H-2q and H-2r haplotypes. Whereas the role of the H-2A molecule in susceptibility to CIA is well established, little is known about the role of H-2E molecule in the disease. In this study, we analyzed the effect of a transgenic E beta d molecule on CIA susceptibility in a recombinant mouse B10.RQB3, which expresses the CIA susceptible Aq genes and an Eak gene, but does not produce an E molecule since Ebq is nonfunctional. In the presence of an Ebd transgene, a viable E molecule is generated. Whereas B10.RQB3 were susceptible to CIA, B10.RQB3-E beta d+ showed a dramatic reduction in the incidence of arthritis as well as a decrease in the level of anti-mouse and anti-bovine CII antibodies in their serum. No clear cut differences in the expression of T cell receptor (TCR) V beta was observed between E beta d+ and E beta d- transgenic mice. Mechanisms underlying the protective effect of E beta d transgenic molecule on CIA may shed light on how HLA-DR molecules influence human RA.Keywords:
BETA (programming language)
Histocompatibility
Backgroud T lymphocytes expressing the γδ-type of T cell receptors (TCR) for antigens contribute to all aspects of immune responses,including defenses against pathogene,tumors,allergy and autoimmunity,and major histocompatibility complex (MHC) Ⅰ molecules is one of major γδTCR ligands.Objective Multiple subsets have been individualized in humans as well as in mice and they appear to recognize in a TCR-dependent manner antigens implying diverse modes of antigen recognition.Reviewing the MHC Ⅰ molecules as one of major γδTCR ligands which is one way of discussing the possible character of γδTCR and γδT cells antigen recognition modes.Content The review introduces the character of γδT cells,then describes MHC Ⅰ molecules that can be recognized as ligands of γδTCR.Trend It is important that confirming the modes of γδT cells antigen recognition further more by the study of MHC Ⅰ molecules as specific ligands of γδ TCR.
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γδT-Cell; Major histocompatibility complex Ⅰ ; Ligand; Antigen recognition
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The T cell repertoire is shaped by positive and negative selection of thymocytes through the interaction of α/β-T cell receptors (TCR) with self-peptides bound to self-major histocompatibility complex (MHC) molecules. However, the involvement of specific TCR-peptide contacts in positive selection remains unclear. By fixing TCR-β chains with a single rearranged TCR-β irrelevant to the selecting ligand, we show here that T cells selected to mature on a single MHC–peptide complex express highly restricted TCR-α chains in terms of Vα usage and amino acid residue of their CDR3 loops, whereas such restriction was not observed with those selected by the same MHC with diverse sets of self-peptides including this peptide. Thus, we visualized the TCR structure required to survive positive selection directed by this single ligand. Our findings provide definitive evidence that specific recognition of self-peptides by TCR could be involved in positive selection of thymocytes.
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The T cell antigen receptor (TCR) recognizes antigen in the form short peptides bound to a major histocompatibility (MHC) molecule. This review provides a synopsis of the current state of knowledge of the structure and function of the receptor and its possible role in human disease. Analysis of the T cell receptor usage of T-cell lines and clones recognizing the same peptide-MHC complex is beginning to shed light onto the structural basis of the TCR-peptide-MHC complex. Also, it is now apparent that there are two mechanisms by which the TCR can interact with the MHC molecule, either through classical peptide interactions or through superantigens. Finally, we review the role of specific TCRs in human disease. Current evidence in this area is difficult to interpret; however, it is likely that TCR-mediatedi sease susceptibility exists, and its basis at either a germline or somatic level will soon be clarified.
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Abstract T cell receptors (TCR) identify target cells presenting a ligand consisting of a major histocompatibility complex molecule (MHC) and an antigenic peptide. A considerable amount of evidence indicates that the TCR contacts both the peptide and the MHC components of the ligand. In fully differentiated T cells the interaction between the peptide and the TCR makes the critical contribution to eliciting a cellular response. However, during the positive selection of thymocytes the contribution of peptide relative to MHC is less well established. Indeed it has been suggested that the critical interaction for positive selection is between the TCR and the MHC molecule and that peptides can be viewed as either allowing or obstructing this contact. This predicts that a given TCR is capable of engaging multiple MHC/peptide complexes. In this study a system is described which detects simply engagement of the TCR by MHC/peptide complexes rather than the functional outcome of such interactions. Using this approach the extent to which peptides can influence contacts between the TCR and the MHC molecule has been examined. The results show that the TCR does in fact engage a wide range of ligands in an MHC‐restricted but largely peptide‐independent manner, suggesting that only a few peptides are able to prevent the TCR from contacting the MHC molecule.
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We review recent data that increase our understanding of the ternary complex of the T cell receptor (TCR), antigenic peptides, and molecules of the major histocompatibility complex (MHC). Studies using synthetic peptide analogs for T-cell antigens have identified peptide residues that appear to interact with the MHC molecule and/or the TCR. The logical extension of these studies, using a complete replacement set of peptide analogues for a model peptide antigen, has more precisely defined the biochemical character of putative MHC and TCR contact residues, and indicated that the TCR is highly sensitive to subtle changes in peptide conformation. Insight into the binding site for peptide on the TCR has recently come from variant peptide immunization of TCR single-chain transgenic mice. These experiments indicate that residues encoded by the V(D)J junctions of both TCR chains contact peptide directly. TCR-MHC contacts have also been studied, using in vitro-mutagenized MHC molecules, particularly those altered at residues predicted to point "up," toward the TCR. These studies reveal that TCR-MHC contacts appear to be quite flexible, and vary between even closely related TCRs. A measure of the affinity of TCR for peptide/MHC complexes has come from competition experiments using soluble MHC complexed with specific peptides. This affinity, with a KD of 5 x 10(-5) M, is several orders of magnitude lower than that of most antibodies for their protein antigens and suggests that the sequence of events leading to T-cell activation begins with antigen-independent adhesion.
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The interaction between T-cell receptors (TCRs) and major histocompatibility complex (MHC)-bound epitopes is one of the most important processes in the adaptive human immune response. Several hypotheses on TCR triggering have been proposed. Many of them involve structural and dynamical adjustments in the TCR/peptide/MHC interface. Molecular Dynamics (MD) simulations are a computational technique that is used to investigate structural dynamics at atomic resolution. Such simulations are used to improve understanding of signalling on a structural level. Here we review how MD simulations of the TCR/peptide/MHC complex have given insight into immune system reactions not achievable with current experimental methods. Firstly, we summarize methods of TCR/peptide/MHC complex modelling and TCR/peptide/MHC MD trajectory analysis methods. Then we classify recently published simulations into categories and give an overview of approaches and results. We show that current studies do not come to the same conclusions about TCR/peptide/MHC interactions. This discrepancy might be caused by too small sample sizes or intrinsic differences between each interaction process. As computational power increases future studies will be able to and should have larger sample sizes, longer runtimes and additional parts of the immunological synapse included.
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The main functions of the T-cell receptor (TCR) involve its specific interaction with short and linear antigenic peptides bound to the major histocompatibility complex (MHC) molecules.In the absence of a 3D structure for TCR and for the TCR/peptide/MHC complex, several attempts to characterize the structural components of the TCR/peptide/MHC interaction have been made.However, this subject is still troublesome.In this paper a computer-based 3D model for a TCR/peptide/MHC complex (5C.C7/moth cytochrome c [MCC] peptide 93-103/I-Ek) was obtained.The complex surface shows a high complementarity between the 5C.C7 structure and the peptide/I-Ek molecule.The mapping of residues involved in the TCR/peptide/MHC interaction shows close agreement with mutational experiments (Jorgensen JL, Reay PA, Ehrich EW, Davis MM, 1992b, Annu Rev Immunol10:835-873).Moreover, the results are consistent with a recent variability analysis of TCR sequences using three variability indexes (Almagro JC, Zenteno-Cuevas R, Vargas-Madrazo E, Lara-Ochoa F, 1995b, Int J Pept Protein Res 45:180-186).Accordingly, the 3D model of the 5C.C7/MCC peptide 93-103/I-Ek complex provides a framework to generate testable hypotheses about TCR recognition.Thus, starting from this model, the role played by each loop that forms the peptide/MHC binding site of the TCR is discussed.
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αβ T cell receptors (TCRs) are genetically restricted to corecognize peptide antigens bound to self-major histocompatibility complex (pMHC) molecules; however, the basis for this MHC specificity remains unclear. Despite the current dogma, evaluation of the TCR–pMHC-I structural database shows that the nongermline-encoded complementarity-determining region (CDR)-3 loops often contact the MHC-I, and the germline-encoded CDR1 and -2 loops frequently participate in peptide-mediated interactions. Nevertheless, different TCRs adopt a roughly conserved docking mode over the pMHC-I, in which three MHC-I residues (65, 69, and 155) are invariably contacted by the TCR in one way or another. Nonetheless, the impact of mutations at these three positions, either individually or together, was not uniformly detrimental to TCR recognition of pHLA-B*0801 or pHLA-B*3508. Moreover, when TCR–pMHC-I recognition was impaired, this could be partially restored by expression of the CD8 coreceptor. The structure of a TCR–pMHC-I complex in which these three (65, 69, and 155) MHC-I positions were all mutated resulted in shifting of the TCR footprint relative to the cognate complex and formation of compensatory interactions. Collectively, our findings reveal the inherent adaptability of the TCR in maintaining peptide recognition while accommodating changes to the central docking site on the pMHC-I.
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