Abstract
The invariant chain (Ii) has pleiotropic functions and is a key factor in antigen presentation. Ii associates with major histocompatibility complex class II molecules in the endoplasmic reticulum (ER) and targets the complex in the endocytic pathway to allow antigenic peptide loading. The human Iip35 isoform includes a cytoplasmic extension containing a di-arginine motif causing ER retention. This minor isoform does not exist in mice and its function in humans has not been thoroughly investigated. We have recently generated transgenic mice expressing Iip35 and these were crossed with Ii-deficient mice to generate animals (Tgp35/mIiKO) expressing exclusively the human isoform. In these mice, we show that Iip35 is expressed in antigen presenting cells and is inducible by interferon gamma (IFN-γ). Despite the low constitutive expression of the protein and some minor differences in the Vβ repertoire of Tgp35/mIiKO mice, Iip35 restored thymic selection of CD4(+) T cells and of invariant natural killer T cells. In vitro functional assays using purified primary macrophages treated with IFN-γ showed that Iip35 allows presentation of an Ii-dependent ovalbumin T-cell epitope. Altogether, our results suggest that Iip35 is functional and does not require co-expression of other isoforms for antigen presentation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antigen Presentation / drug effects
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Antigen Presentation / immunology*
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Antigen-Presenting Cells / drug effects
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Antigen-Presenting Cells / immunology
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Antigen-Presenting Cells / metabolism
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Antigens, Differentiation, B-Lymphocyte / genetics
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Antigens, Differentiation, B-Lymphocyte / immunology*
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Antigens, Differentiation, B-Lymphocyte / metabolism
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CD4-Positive T-Lymphocytes / immunology
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CD4-Positive T-Lymphocytes / metabolism
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Cells, Cultured
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Female
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Flow Cytometry
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Histocompatibility Antigens Class II / genetics
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Histocompatibility Antigens Class II / immunology*
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Histocompatibility Antigens Class II / metabolism
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Humans
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Interferon-gamma / immunology
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Interferon-gamma / pharmacology
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Macrophages / drug effects
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Macrophages / immunology
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Macrophages / metabolism
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Male
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Mice, Transgenic
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Natural Killer T-Cells / immunology
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Natural Killer T-Cells / metabolism
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Ovalbumin / immunology
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Protein Isoforms / genetics
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Protein Isoforms / immunology
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Protein Isoforms / metabolism
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Receptors, Antigen, T-Cell / immunology
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Receptors, Antigen, T-Cell / metabolism
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Thymocytes / immunology
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Thymocytes / metabolism
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Thymus Gland / cytology
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Thymus Gland / immunology*
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Thymus Gland / metabolism
Substances
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Antigens, Differentiation, B-Lymphocyte
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Histocompatibility Antigens Class II
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Protein Isoforms
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Receptors, Antigen, T-Cell
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invariant chain
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Interferon-gamma
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Ovalbumin