Distinct orientation of the alloreactive monoclonal CD8 T cell activation program by three different peptide/MHC complexes

Centre d'Immunologie de Marseille-Luminy, CNRS-INSERM-Universite de la Méditerranée, Campus de Luminy, Marseille, France.
European Journal of Immunology (Impact Factor: 4.03). 08/2006; 36(7):1856-66. DOI: 10.1002/eji.200635895
Source: PubMed


We have characterized three different programs of activation for alloreactive CD8 T cells expressing the BM3.3 TCR, their elicitation depending on the characteristics of the stimulating peptide/MHC complex. The high-affinity interaction between the TCR and the K(b)-associated endogenous peptide pBM1 (INFDFNTI) induced a complete differentiation program into effector cells correlated with sustained ERK activation. The K(bm8) variant elicited a partial activation program with delayed T cell proliferation, poor CTL activity and undetectable ERK phosphorylation; this resulted from a low-avidity interaction of TCR BM3.3 with a newly identified endogenous peptide, pBM8 (SQYYYNSL). Interestingly, mismatched pBM1/K(bm8) complexes induced a split response in BM3.3 T cells, with total reconstitution of T cell proliferation but defective generation of CTL activity that was correlated with strong but shortened ERK phosphorylation. Crystal structures highlight the molecular basis for the higher stability of pBM8/K(bm8) compared to pBM1/K(bm8) complexes that exist in two conformers. This study illustrates the importance of the stability of both peptide/MHC and peptide/MHC-TCR interactions for induction of sustained signaling required to induce optimal CTL effector functions. Subtle allelic structural variations, amplified by peptide selection, may thus orient distinct outcomes of alloreactive TCR-based therapies.

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    • "Alloreactive TCR BM3.3 murine hybridomas were used. TCR BM3.3 recognizes its agonist pBM1/H2-Kb with high avidity in a CD8 co-receptor independent fashion for long term consequences of recognition [27], [28], [43], [55]. The 4C8.98 hybridoma was obtained by fusion between spleen cells from a Rag1-/- BM3.3-TCR-transgenic mice and BW-TCRα-/β-. "
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    ABSTRACT: The rupture forces and adhesion frequencies of single recognition complexes between an affinity selected peptide/MHC complex and a TCR at a murine hybridoma surface were measured using Atomic Force Microscopy. When the CD8 coreceptor is absent, the adhesion frequency depends on the nature of the peptide but the rupture force does not. When CD8 is present, no effect of the nature of the peptide is observed. CD8 is proposed to act as a time and distance lock, enabling the shorter TCR molecule to bridge the pMHC and have time to finely read the peptide. Ultimately, such experiments could help the dissection of the sequential steps by which the TCR reads the peptide/MHC complex in order to control T cell activation.
    Preview · Article · Jul 2011 · PLoS ONE
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    • "Structural model of murine MHC I molecule H2-Kb with bound octapeptide SQYYYNSL. (a) Crystal structure model of H2-Kb with bound octapeptide SQYYYNSL (PDB entry 2clv [33]). Top view of the peptide binding groove: red: alpha helices; yellow: beta sheets; blue: octapeptide SQYYYNSL, amino acids of the anchor positions are shown as sticks. "
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    ABSTRACT: Experimental results are presented for 180 in silico designed octapeptide sequences and their stabilizing effects on the major histocompatibility class I molecule H-2K(b). Peptide sequence design was accomplished by a combination of an ant colony optimization algorithm with artificial neural network classifiers. Experimental tests yielded nine H-2K(b) stabilizing and 171 nonstabilizing peptides. 28 among the nonstabilizing octapeptides contain canonical motif residues known to be favorable for MHC I stabilization. For characterization of the area covered by stabilizing and non-stabilizing octapeptides in sequence space, we visualized the distribution of 100,603 octapeptides using a self-organizing map. The experimental results present evidence that the canonical sequence motives of the SYFPEITHI database on their own are insufficient for predicting MHC I protein stabilization.
    Full-text · Article · May 2010 · BioMed Research International
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    • "BM3.3 CD8 T-cell effectors have been obtained after 3 days in vitro stimulation of naı¨ve T cells derived from mice transgenic for the BM3.3 TCR using either H-2K bm8 -positive antigen-presenting cells in the presence of IL-2, or H-2K b -positive antigen-presenting cells. Cytotoxic activity was tested on 51 Cr-labelled (sodium chromate, NEN, MA) Tap-2-deficient H-2 b RMA-S cells and on H-2K b -negative, H-2K bm8 -expressing RMA-S targets (Auphan-Anezin et al, 2006), during a 4 h incubation. "
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    ABSTRACT: Binding degeneracy is thought to constitute a fundamental property of the T-cell antigen receptor (TCR), yet its structural basis is poorly understood. We determined the crystal structure of a complex involving the BM3.3 TCR and a peptide (pBM8) bound to the H-2K(bm8) major histocompatibility complex (MHC) molecule, and compared it with the structures of the BM3.3 TCR bound to H-2K(b) molecules loaded with two peptides that had a minimal level of primary sequence identity with pBM8. Our findings provide a refined structural view of the basis of BM3.3 TCR cross-reactivity and a structural explanation for the long-standing paradox that a TCR antigen-binding site can be both specific and degenerate. We also measured the thermodynamic features and biological penalties that incurred during cross-recognition. Our data illustrate the difficulty for a given TCR in adapting to distinct peptide-MHC surfaces while still maintaining affinities that result in functional in vivo responses. Therefore, when induction of protective effector T cells is used as the ultimate criteria for adaptive immunity, TCRs are probably much less degenerate than initially assumed.
    Full-text · Article · May 2007 · The EMBO Journal
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