Abstract
By stimulating human CD8(+) T lymphocytes with autologous dendritic cells infected with an adenovirus encoding MAGE-3, we obtained a cytotoxic T lymphocyte (CTL) clone that recognized a new MAGE-3 antigenic peptide, AELVHFLLL, which is presented by HLA-B40. This peptide is also encoded by MAGE-12. The CTL clone recognized MAGE-3--expressing tumor cells only when they were first treated with IFN-gamma. Since this treatment is known to induce the exchange of the three catalytic subunits of the proteasome to form the immunoproteasome, this result suggested that the processing of this MAGE-3 peptide required the immunoproteasome. Transfection experiments showed that the substitution of beta5i (LMP7) for beta5 is necessary and sufficient for producing the peptide, whereas a mutated form of beta5i (LMP7) lacking the catalytically active site was ineffective. Mass spectrometric analyses of in vitro digestions of a long precursor peptide with either proteasome type showed that the immunoproteasome produced the antigenic peptide more efficiently, whereas the standard proteasome more efficiently introduced cleavages destroying the antigenic peptide. This is the first example of a tumor-specific antigen exclusively presented by tumor cells expressing the immunoproteasome.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenoviridae / genetics
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Amino Acid Sequence
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Animals
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Antigen Presentation
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Antigens, Neoplasm / chemistry
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Antigens, Neoplasm / genetics
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Antigens, Neoplasm / immunology*
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Antigens, Neoplasm / metabolism
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COS Cells
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Clone Cells / enzymology
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Clone Cells / immunology
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Clone Cells / metabolism
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Cysteine Endopeptidases / chemistry
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Cysteine Endopeptidases / metabolism*
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Cytokines / immunology
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Cytotoxicity, Immunologic
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Dendritic Cells / immunology
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HLA-B Antigens / immunology*
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HLA-B40 Antigen
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Humans
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Molecular Sequence Data
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Multienzyme Complexes / chemistry
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Multienzyme Complexes / metabolism*
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Neoplasm Proteins / chemistry
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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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Peptide Fragments / chemistry
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Peptide Fragments / genetics
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Peptide Fragments / immunology
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Peptide Fragments / metabolism
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Proteasome Endopeptidase Complex
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Protein Processing, Post-Translational
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Protein Subunits
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T-Lymphocytes, Cytotoxic / enzymology*
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T-Lymphocytes, Cytotoxic / immunology*
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T-Lymphocytes, Cytotoxic / metabolism
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Transfection
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Tumor Cells, Cultured
Substances
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Antigens, Neoplasm
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Cytokines
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HLA-B Antigens
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HLA-B40 Antigen
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MAGEA3 protein, human
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Multienzyme Complexes
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Neoplasm Proteins
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Peptide Fragments
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Protein Subunits
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Cysteine Endopeptidases
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Proteasome Endopeptidase Complex