Lck Availability during Thymic Selection Determines the Recognition Specificity of the T Cell Repertoire

Laethem, François Van; Tikhonova, Anastasia; Pobezinsky, Leonid A; Tai, Xuguang; Kimura, Motoko; Saout, Cecile Le; Guinter, Terry I.; Adams, Anthony J.; Sharrow, Susan O.; Bernhardt, Günter; Feigenbaum, Lionel; Singer, Alfred

doi:10.1016/j.cell.2013.08.009

Cited by 96 publications

(106 citation statements)

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“…It is noteworthy that our strategy based on p-MHC tetramer + -cells sorting, naturally skew the analysis toward MHC-restricted thymocytes, excluding potential immature thymocytes expressing nonMHC restricted TCRs [30,31], whose existence are the basis of the selection model of MHC restriction [32]. Our observations would nevertheless better support the assumption that the preselected T-cell repertoire might be inherently prone to interact with MHC molecules, as proposed by various groups in the TCR/MHC coevolution theory [33,34].…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, as the hierarchy of recognition also correlates with the efficacy of thymic selection in A2 − donors, it is also tempting to speculate that frequently recognized complexes, like MelA-A2 and PGT-A2, are more structurally related to a conserved p-MHC topology found in the thymic microenvironment of both A2 + and A2 − donors, than less frequently recognized complexes, like pp65-A2 and Gag-A2. Finally, our quantitative analysis revealed an unexpectedly high frequency of MHC-restricted thymocytes in the DP compartment ranging from 10 −6 to 10 −5 in donors expressing or not HLA-A2.It is noteworthy that our strategy based on p-MHC tetramer + -cells sorting, naturally skew the analysis toward MHC-restricted thymocytes, excluding potential immature thymocytes expressing nonMHC restricted TCRs [30,31], whose existence are the basis of the selection model of MHC restriction [32]. Our observations would nevertheless better support the assumption that the preselected T-cell repertoire might be inherently prone to interact with MHC molecules, as proposed by various groups in the TCR/MHC coevolution theory [33,34].…”

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confidence: 99%

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Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

et al. 2015

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In the thymus, a T-cell repertoire able to confer protection against infectious and noninfectious agents in a peptide-dependent, self-MHC-restricted manner is selected. Direct detection of Ag-specific thymocytes, and analysis of the impact of the expression of the MHCrestricting allele on their frequency or function has never been studied in humans because of the extremely low precursor frequency. Here, we used a tetramer-based enrichment protocol to analyze the ex vivo frequency and activation-phenotype of human thymocytes specific for self, viral and tumor-antigens presented by HLA-A*0201 (A2) in individuals expressing or not this allele. Ag-specific thymocytes were quantified within both CD4CD8 double or single-positive compartments in every donor. Our data indicate that the maturation efficiency of Ag-specific thymocytes is poorly affected by HLA-A2 expression, in terms of frequencies. Nevertheless, A2-restricted T-cell lines from A2 + donors reacted to A2 + cell lines in a highly peptide-specific fashion, whereas their alloreactive counterparts showed off-target activity. This first ex vivo analysis of human antigen-specific thymocytes at different stages of human T-cell development should open new perspectives in the understanding of the human thymic selection process. Keywords: Antigen r Human T cells r MHC r Tetramers r Thymocytes See accompanying Commentary by Ciucci and BosselutAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionThe thymus generates a highly diverse T-cell repertoire able to recognize virtually any antigen that could be encountered by a given individual along his/her life. This diversity is achieved through two main mechanisms. First by the acquisition by CD4 + CD8 + double-positive (DP) thymocytes of a clonally distributed T cell receptor (TCR) that is generated after somatic recombination of TCR V(D)J gene segments and nontemplated nucleotide Correspondence: Dr. Xavier Saulquin e-mail: xavier.saulquin@univ-nantes.fradditions. This quasi-random mechanism allows for the generation of up to 10 15 different receptors [1]. Second, by the shaping of this initial T-cell repertoire by positive and negative thymic selection processes that will favor emergence of a self major histocompatibility molecules (MHC)-restricted, yet self-tolerant, TCR repertoire carried by mature naïve single-positive (SP) T cells. As a consequence of this maturation process, the diversity of SP αβ T cells in a given individual falls in the range of 10 6 to 10 8 [2]. * LH and FL equally contributed to this work. The respective contributions of positive and negative thymic selection processes to the generation of a mature T-cell repertoire possibly biased towards recognition of peptides restricted by host MHC alleles are still debated. Indeed, this phenomenon referred to as "host or Self-MHC-restriction" is a consequence of a balance between (i) the need for a thymocyte to get survival signals from TCR upon interactions of weak/intermediate avidi...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

et al. 2015

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“…Most dramatically, one laboratory constructed a mouse lacking MHCI, MHCII, CD4, and CD8 and introduced mutations to uncouple essential downstream TCR-signaling molecules from essential interactions (47)(48)(49). The mice developed a peripheral T-cell repertoire that contains T cells reactive to the surface protein CD155.…”

Section: Discussionmentioning

confidence: 99%

Class II major histocompatibility complex mutant mice to study the germ-line bias of T-cell antigen receptors

Silberman

Krovi

Tuttle

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The interaction of αβ T-cell antigen receptors (TCRs) with peptides bound to MHC molecules lies at the center of adaptive immunity. Whether TCRs have evolved to react with MHC or, instead, processes in the thymus involving coreceptors and other molecules select MHC-specific TCRs de novo from a random repertoire is a longstanding immunological question. Here, using nuclease-targeted mutagenesis, we address this question in vivo by generating three independent lines of knockin mice with single-amino acid mutations of conserved class II MHC amino acids that often are involved in interactions with the germ-line-encoded portions of TCRs. Although the TCR repertoire generated in these mutants is similar in size and diversity to that in WT mice, the evolutionary bias of TCRs for MHC is suggested by a shift and preferential use of some TCR subfamilies over others in mice expressing the mutant class II MHCs. Furthermore, T cells educated on these mutant MHC molecules are alloreactive to each other and to WT cells, and vice versa, suggesting strong functional differences among these repertoires. Taken together, these results highlight both the flexibility of thymic selection and the evolutionary bias of TCRs for MHC.T he genes for immunoglobulins (Igs), αβ T-cell receptors (TCRs), and antigen-presenting MHC proteins appeared at least 450 million years ago in the cartilaginous fish and are present in all modern vertebrates (1-3). The more primitive hagfish and lampreys lack these genes and have an adaptive immune system comprised of unrelated proteins (4). The main ligands for αβ TCRs are short peptides derived from self and foreign proteins, captured in a specialized groove of MHC class I (MHCI) and class II (MHCII) molecules and presented to T cells (5, 6). Functional Igs and TCRs are created by very similar recombination mechanisms involving fusion of V, J, and sometimes D gene segments with additional variations at the junctions to create an enormous potential repertoire of Igs and TCRs, suggesting a common, unknown evolutionary origin for these loci.These observations have raised several unanswered questions. For example,why did a separate TCR-rearranging gene system develop for lymphocytes recognizing peptide-MHC ligands? How did the extraordinarily polymorphic MHC genes stay functionally connected to TCR genes throughout 450 million years of evolution? One long-standing hypothesis has been that certain features of TCRs and MHC molecules are evolutionarily conserved to promote their interaction (7-10). Like Igs, the antigen-recognition portions of TCRs are partially encoded in the complementary determining region (CDR) CDR1 and CDR2 loops of germ-line TCR Vα (TRAV) and Vβ (TRBV) genes and are partially generated by somatic recombination processes that form the CDR3 loops. This initial repertoire is culled dramatically during T-cell development in the thymus. First, only those T cells whose TCRs have at least some minimal affinity for the selfpeptide-MHC molecules expressed in the thymus are positively selected for fu...

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“…But this is taken as supporting either model, as germ line-encoded contacts are likely to be required to allow the formation of a TCR-CD3-pMHC-CD4/CD8 macrocomplex that situates the CD3 ITAMs and Lck in a functionally mandated orientation (1-4, 6, 9, 10). Structural insights from positively selected TCRs thus do not allow the basis of MHC restriction to be cleanly addressed, and functional data that support either model have been reported (11)(12)(13)(14)(15).…”

Section: Cd8mentioning

confidence: 99%

Functional evidence for TCR-intrinsic specificity for MHCII

Parrish

Deshpande

Vasic

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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How T cells become restricted to binding antigenic peptides within class I or class II major histocompatibility complex molecules (pMHCI or pMHCII, respectively) via clonotypic T-cell receptors (TCRs) remains debated. During development, if TCR-pMHC interactions exceed an affinity threshold, a signal is generated that positively selects the thymocyte to become a mature CD4 + or CD8 + T cell that can recognize foreign peptides within MHCII or MHCI, respectively. But whether TCRs possess an intrinsic, subthreshold specificity for MHC that facilitates sampling of the peptides within MHC during positive selection or T-cell activation is undefined. Here we asked if increasing the frequency of lymphocyte-specific protein tyrosine kinase (Lck)-associated CD4 molecules in T-cell hybridomas would allow for the detection of subthreshold TCR-MHC interactions. The reactivity of 10 distinct TCRs was assessed in response to selecting and nonselecting MHCII bearing cognate, null, or "shaved" peptides with alanine substitutions at known TCR contact residues: Three of the TCRs were selected on MHCII and have defined peptide specificity, two were selected on MHCI and have a known pMHC specificity, and five were generated in vitro without defined selecting or cognate pMHC. Our central finding is that IL-2 was made when each TCR interacted with selecting or nonselecting MHCII presenting shaved peptides. These responses were abrogated by anti-CD4 antibodies and mutagenesis of CD4. They were also inhibited by anti-MHC antibodies that block TCR-MHCII interactions. We interpret these data as functional evidence for TCR-intrinsic specificity for MHCII.TCR | MHC | restriction | CD4 | Lck P ositive and negative selection limit the αβT-cell repertoire to cells expressing clonotypic T-cell receptors (TCRs) that distinguish the antigenicity of peptides embedded within class I and class II major histocompatibility complex molecules (pMHCI or pMHCII, respectively) based on their source of origin (i.e., self or foreign) (1-4). Approximately 7.5% of CD4 + CD8+ doublepositive (DP) thymocytes express TCRs that interact with selfpMHC above an affinity threshold required for positive selection, whereas 7.5% cross a higher affinity threshold that mediates negative selection and the remaining TCRs fail to direct positive selection (5). The rules that restrict TCR recognition of antigenic peptides within MHCI or MHCII are unresolved.Two models have been proposed to explain MHC restriction. One posits that restriction is imposed by CD4 or CD8 during thymocyte development to eliminate TCRs that recognize non-MHC ligands (2, 6). Here, the CD4-and CD8-associated Src kinase, p56Lck [lymphocyte-specific protein tyrosine kinase (Lck)], is sequestered away from the immunoreceptor tyrosine-based activation motifs (ITAMs) of the TCR-associated CD3δe, CD3γe, and CD3ζζ signaling modules. Positively selecting signals are then generated in thymocytes expressing TCRs that bind MHCII or MHCI together with CD4 or CD8, respectively, as this localizes Lck to the ITAMs. T...

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Lck Availability during Thymic Selection Determines the Recognition Specificity of the T Cell Repertoire

Cited by 96 publications

References 40 publications

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

Class II major histocompatibility complex mutant mice to study the germ-line bias of T-cell antigen receptors

Functional evidence for TCR-intrinsic specificity for MHCII

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