title: Elongated TCR alpha chain CDR3 favors an altered CD4 cytokine profile.
abstract: BACKGROUND
  CD4 T lymphocyte activation requires T cell receptor (TCR) engagement by peptide/MHC (major histocompatibility complex) (pMHC). The TCR complementarity-determining region 3 (CDR3) contains variable α and β loops critical for pMHC recognition. During any immune response, tuning of TCR usage through progressive clonal selection occurs. Th1 and Th2 cells operate at different avidities for activation and display distinct transcriptional programs, although polarization may be plastic, influenced by pathogens and cytokines. We therefore hypothesized that CDR3αβ sequence features may intrinsically influence CD4 phenotype during progression of a response.
  
  
  RESULTS
  We show that CD4 polarization involves distinct CDR3α usage: Th1 and Th17 cells favored short TCR CDR3α sequences of 12 and 11 amino acids, respectively, while Th2 cells favored elongated CDR3α loops of 14 amino acids, with lower predicted affinity. The dominant Th2- and Th1-derived TCRα sequences with 14 amino acid CDR3 loops and 12 amino acid CDR3 loops, respectively, were expressed in TCR transgenics. The functional impact of these TCRα transgenes was assessed after in vivo priming with a peptide/adjuvant. The short, Th1-derived receptor transgenic T cell lines made IFNγ, but not IL-4, 5 or 13, while the elongated, Th2-derived receptor transgenic T cell lines made little or no IFNγ, but increased IL-4, 5 and 13 with progressive re-stimulations, mirrored by GATA-3 up-regulation. T cells from primed Th2 TCRα transgenics selected dominant TCR Vβ expansions, allowing us to generate TCRαβ transgenics carrying the favored, Th2-derived receptor heterodimer. Primed T cells from TCRαβ transgenics made little or no IL-17 or IFNγ, but favored IL-9 after priming with Complete Freund's adjuvant and IL-4, 5, 9, 10 and 13 after priming with incomplete Freund's. In tetramer-binding studies, this transgenic receptor showed low binding avidity for pMHC and polarized T cell lines show TCR avidity for Th17 > Th1 > Th2. While transgenic expression of a Th2-derived, 'elongated' TCR-CDR3α and the TCRαβ pair, clearly generated a program shifted away from Th1 immunity and with low binding avidity, cytokine-skewing could be over-ridden by altering peptide challenge dose.
  
  
  CONCLUSIONS
  We propose that selection from responding clones with distinctive TCRs on the basis of functional avidity can direct a preference away from Th1 effector responses, favoring Th2 cytokines.
authors.forename: Catherine
authors.initials: C
authors.lastname: Reynolds
authors.forename: Deborah
authors.initials: D
authors.lastname: Chong
authors.forename: Eleanor
authors.initials: E
authors.lastname: Raynsford
authors.forename: Kathryn
authors.initials: K
authors.lastname: Quigley
authors.forename: Deborah
authors.initials: D
authors.lastname: Kelly
authors.forename: Julia
authors.initials: J
authors.lastname: Llewellyn-Hughes
authors.forename: Daniel
authors.initials: D
authors.lastname: Altmann
authors.affiliation: Lung Immunology Group, Infectious Diseases and Immunity, Department of Medicine, Imperial College, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK. r.boyton@imperial.ac.uk.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Boyton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002460:Cell Line; D016764:Cell Polarity; D022801:Complementarity Determining Regions / Q000737:chemistry / Q000378:metabolism*; D045142:Cross-Priming; D016207:Cytokines / Q000378:metabolism*; D007114:Immunization; D007371:Interferon-gamma / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018448:Models, Immunological; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D010641:Phenotype; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry* / Q000378:metabolism*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
chemical_list: D022801:Complementarity Determining Regions; D016207:Cytokines; D010455:Peptides; D016693:Receptors, Antigen, T-Cell, alpha-beta; D007371:Interferon-gamma