title: Analysis of the TCR alpha-chain rearrangement profile in human T lymphocytes.
abstract: The size of the available human alphabeta T cell repertoire is difficult to determine and is open to debate. Empirical analysis of TCR beta-chain diversity reveals approximately 10(6) different beta chains in peripheral blood. Due in part to locus complexity, comparable information for TCR alpha is lacking. Rather, current estimates for human TCR alpha diversity, and hence, total repertoire diversity, are based on theoretical analyses that assume equal probabilities of rearrangement between any V alpha gene and J alpha gene. Here, we report on a systematic locus-wide rearrangement analysis of the TCR alpha-chain in human T cells. We first demonstrate that the V-J alpha recombination in the thymus is not random but depends on the reciprocal V alpha and J alpha position within the locus. Characterization of the frequency of gene usage combined with identification of five previously unrecognized pseudogenes enables us to empirically estimate the human TCR alpha combinatorial repertoire. The number of V-J alpha combinations achieved is approximately 44-56% of the total combinatorial possibilities, significantly lower than theoretical estimates. We also demonstrate that TCR alpha-chain diversity in peripheral T lymphocytes mimics the same general patterns of rearrangement as observed in the thymus, and these patterns appear conserved among different individuals. This unexpected observation indicates that, unlike the TCR beta locus, the human TCR alpha-chain repertoire is primarily predetermined by genetic recombination and its size is restricted by limits on the combinatorial repertoire rather than post-thymic selection.
authors: Laboratoire d'Immunochimie, Commissariat à l'Energie Atomique-Grenoble/Département des Réponses et Dynamique Cellulaire, Institut National de la Santé Et de la Recherche Médicale, U548, Grenoble, France. paf23@pitt.edu
authors: Patrizia
authors: P
authors: Fuschiotti
authors: Nicolas
authors: N
authors: Pasqual
authors: Vivien
authors: V
authors: Hierle
authors: Eve
authors: E
authors: Borel
authors: Jacqueline
authors: J
authors: London
authors: Patrice Noël
authors: PN
authors: Marche
authors: Evelyne
authors: E
authors: Jouvin-Marche
mesh_terms: D000328:Adult; D017124:Conserved Sequence; D005260:Female; D015332:Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor; D005819:Genetic Markers / Q000235:genetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics*; D011995:Recombination, Genetic; D013601:T-Lymphocytes / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism*; D013950:Thymus Gland / Q000737:chemistry / Q000166:cytology / Q000378:metabolism
chemical_list: D005819:Genetic Markers; D016693:Receptors, Antigen, T-Cell, alpha-beta