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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Antigens, Neoplasm
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Autoantigens / genetics
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Autoantigens / immunology*
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Autoantigens / metabolism
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Cell Differentiation / genetics
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Cell Differentiation / immunology
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Clone Cells
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Cytotoxicity, Immunologic / genetics
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Epitopes, T-Lymphocyte / biosynthesis
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Epitopes, T-Lymphocyte / genetics
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Epitopes, T-Lymphocyte / immunology*
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Epitopes, T-Lymphocyte / metabolism
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Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor / physiology*
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Gene Rearrangement, beta-Chain T-Cell Antigen Receptor / physiology
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HLA-A2 Antigen / biosynthesis
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HLA-A2 Antigen / genetics
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HLA-A2 Antigen / immunology*
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HLA-A2 Antigen / metabolism
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Hematopoietic Stem Cells / immunology
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Hematopoietic Stem Cells / metabolism
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Humans
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MART-1 Antigen
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Melanoma / genetics
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Melanoma / immunology*
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Molecular Sequence Data
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Neoplasm Proteins / genetics
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Neoplasm Proteins / immunology*
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Neoplasm Proteins / metabolism
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RNA, Messenger / analysis
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Receptors, Antigen, T-Cell, alpha-beta / biosynthesis
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Receptors, Antigen, T-Cell, alpha-beta / genetics
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Receptors, Antigen, T-Cell, alpha-beta / physiology*
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Reverse Transcriptase Polymerase Chain Reaction
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T-Lymphocytes, Cytotoxic / immunology
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T-Lymphocytes, Cytotoxic / metabolism
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Tumor Cells, Cultured
Substances
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Antigens, Neoplasm
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Autoantigens
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Epitopes, T-Lymphocyte
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HLA-A2 Antigen
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MART-1 Antigen
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MLANA protein, human
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Neoplasm Proteins
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RNA, Messenger
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Receptors, Antigen, T-Cell, alpha-beta