title: Restrictions in the repertoire of allospecific T cells. Contribution of the alpha-helical sequence polymorphism of HLA-DR molecules.
abstract: We have studied the molecular diversity of the allogeneic TCR repertoire specific for the HLA-DR4 variant, DRB1*0404, by analyzing the V beta gene segment usage of CD4+ T cell clones from nine different donors and comparing the V beta repertoire in allospecific and unselected T cell populations. To investigate the forces shaping the repertoire of the alloreactive T cell response we compared the diversity of TCR specificities utilized in very similar and in disparate responder/stimulator combinations. Six of the responders shared the HLA-DRB1*0401 allele, which differs from the HLA-DRB1*0404 allele by only two amino acid substitutions at positions 71 and 86 of the HLA-DR beta 1 chain; three responders expressed HLA-DRB1 alleles with extensive polymorphisms compared with the stimulator HLA-DRB1 allele. In all nine responders, TCR specificities recruited to recognize HLA-DRB1*0404 were strongly biased toward the dominant usage of one to three V beta elements. Despite some degree of heterogeneity between different responders, the overall pattern was very similar with a hierarchy of TCR V beta elements expressed by HLA-DRB1*0404 specific T cells. A core group of V beta elements (V beta 6, 5, 2, 13.2, 18, and 7) was preferentially used, whereas other V beta elements including V beta 3, 4, and 8 were infrequently used or not used at all. Sequencing of the VDJ beta region from selected T cell clones showed no junctional bias associated with the preferential V beta gene segment usage. Surprisingly, the T cell diversity in focused and in complex alloreactive responses were equally biased. The finding that HLA-DR4+ and DR4- donors exhibited a similar bias supports the interpretation that the alpha-helical HLA-DR structure of the stimulator cell has a dominant contribution in shaping the alloreactive repertoire.
authors.affiliation: Department of Medicine, Mayo Clinic and Foundation, Rochester, MN 55905.
authors.forename: J J
authors.initials: JJ
authors.lastname: Goronzy
authors.forename: C
authors.initials: C
authors.lastname: Xie
authors.forename: W
authors.initials: W
authors.lastname: Hu
authors.forename: S K
authors.initials: SK
authors.lastname: Lundy
authors.forename: C M
authors.initials: CM
authors.lastname: Weyand
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002999:Clone Cells; D006684:HLA-DR Antigens / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D006684:HLA-DR Antigens; D016693:Receptors, Antigen, T-Cell, alpha-beta