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  • Title: Prevalent role of TCR alpha-chain in the selection of the preimmune repertoire specific for a human tumor-associated self-antigen.
    Author: Dietrich PY, Le Gal FA, Dutoit V, Pittet MJ, Trautman L, Zippelius A, Cognet I, Widmer V, Walker PR, Michielin O, Guillaume P, Connerotte T, Jotereau F, Coulie PG, Romero P, Cerottini JC, Bonneville M, Valmori D.
    Journal: J Immunol; 2003 May 15; 170(10):5103-9. PubMed ID: 12734356.
    Abstract:
    The specificity of recognition of pMHC complexes by T lymphocytes is determined by the V regions of the TCR alpha- and beta-chains. Recent experimental evidence has suggested that Ag-specific TCR repertoires may exhibit a more V alpha- than V beta-restricted usage. Whether V alpha usage is narrowed during immune responses to Ag or if, on the contrary, restricted V alpha usage is already defined at the early stages of TCR repertoire selection, however, has remained unexplored. Here, we analyzed V and CDR3 TCR regions of single circulating naive T cells specifically detected ex vivo and isolated with HLA-A2/melan-A peptide multimers. Similarly to what was previously observed for melan-A-specific Ag-experienced T cells, we found a relatively wide V beta usage, but a preferential V alpha 2.1 usage. Restricted V alpha 2.1 usage was also found among single CD8(+) A2/melan-A multimer(+) thymocytes, indicating that V alpha-restricted selection takes place in the thymus. V alpha 2.1 usage, however, was independent from functional avidity of Ag recognition. Thus, interaction of the pMHC complex with selected V alpha-chains contributes to set the broad Ag specificity, as underlined by preferential binding of A2/melan-A multimers to V alpha 2.1-bearing TCRs, whereas functional outcomes result from the sum of these with other interactions between pMHC complex and TCR.
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