title: Allelic exclusion at the TCR delta locus and commitment to gamma delta lineage: different modalities apply to distinct human gamma delta subsets.
abstract: Expression of a beta-chain, as a pre-TCR, in T cell precursors prevents further rearrangements on the alternate beta allele through a strict allelic exclusion process and enables precursors to undergo differentiation. However, whether allelic exclusion applies to the TCR delta locus is unknown and the role of the gamma delta TCR in gamma delta lineage commitment is still unclear. Through the analysis of the rearrangement status of the TCR gamma, delta, and beta loci in human gamma delta T cell clones, expressing either the TCR V delta 1 or V delta 2 variable regions, we show that the rate of partial rearrangements at the delta locus is consistent with an allelic exclusion process. The overrepresentation of clones with two functional TCR gamma chains indicates that a gamma delta TCR selection process is required for the commitment of T cell precursors to the gamma delta lineage. Finally, while complete TCR beta rearrangements were observed in several V delta 2 T cell clones, these were seldom found in V delta 1 cells. This suggests a competitive alpha beta/gamma delta lineage commitment in the former subset and a precommitment to the gamma delta lineage in the latter. We propose that these distinct behaviors are related to the developmental stage at which rearrangements occur, as suggested by the patterns of accessibility to recombination sites that characterize the V delta 1 and V delta 2 subsets.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale Unité 463, Institut de Biologie, Nantes, France.
authors.forename: Chrystelle
authors.initials: C
authors.lastname: Couedel
authors.forename: Eric
authors.initials: E
authors.lastname: Lippert
authors.forename: Karine
authors.initials: K
authors.lastname: Bernardeau
authors.forename: Marc
authors.initials: M
authors.lastname: Bonneville
authors.forename: François
authors.initials: F
authors.lastname: Davodeau
mesh_terms: D000328:Adult; D000483:Alleles; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D002999:Clone Cells; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor; D016694:Gene Rearrangement, delta-Chain T-Cell Antigen Receptor / Q000235:genetics*; D015334:Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor / Q000235:genetics*; D005819:Genetic Markers / Q000276:immunology; D006801:Humans; D007231:Infant, Newborn; D016364:Reading Frames / Q000235:genetics / Q000276:immunology; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000096:biosynthesis / Q000235:genetics*; D011995:Recombination, Genetic / Q000276:immunology; D013234:Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*
chemical_list: D005819:Genetic Markers; D016692:Receptors, Antigen, T-Cell, gamma-delta