title: Tumor cells present MHC class II-restricted nuclear and mitochondrial antigens and are the predominant antigen presenting cells in vivo.
abstract: MHC class II-restricted tumor Ags presented by class II(+) tumor cells identified to date are derived from proteins expressed in the cytoplasm or plasma membrane of tumor cells. It is unclear whether MHC class II(+) tumor cells present class II-restricted epitopes derived from other intracellular compartments, such as nuclei and/or mitochondria, and whether class II(+) tumor cells directly present Ag in vivo. To address these questions, a model Ag, hen egg lysozyme, was targeted to various subcellular compartments of mouse sarcoma cells, and the resulting cells were tested for presentation of three lysozyme epitopes in vitro and for presentation of nuclear Ag in vivo. In in vitro studies, Ags localized to all tested compartments (nuclei, cytoplasm, mitochondria, and endoplasmic reticulum) are presented in the absence invariant chain and H-2M. Coexpression of invariant chain and H-2M inhibit presentation of some, but not all, of the epitopes. In vivo studies demonstrate that class II(+) tumor cells, and not host-derived cells, are the predominant APC for class II-restricted nuclear Ags. Because class II(+) tumor cells are effective APC in vivo and probably present novel tumor Ag epitopes not presented by host-derived APC, their inclusion in cancer vaccines may enhance activation of tumor-reactive CD4(+) T cells.
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore, MD 21250, USA.
authors.forename: L
authors.initials: L
authors.lastname: Qi
authors.forename: J M
authors.initials: JM
authors.lastname: Rojas
authors.forename: S
authors.initials: S
authors.lastname: Ostrand-Rosenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism* / Q000637:transplantation*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis / Q000235:genetics; D002451:Cell Compartmentation / Q000235:genetics / Q000276:immunology; D002467:Cell Nucleus / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D006681:HLA-D Antigens / Q000096:biosynthesis / Q000235:genetics; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006825:Hybridomas; D016056:Immunodominant Epitopes / Q000008:administration & dosage / Q000378:metabolism*; D051379:Mice; D008805:Mice, Inbred A; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D008928:Mitochondria / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D009113:Muramidase / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D009368:Neoplasm Transplantation; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D012513:Sarcoma, Experimental / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000637:transplantation; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D006681:HLA-D Antigens; C084245:HLA-DM antigens; D000949:Histocompatibility Antigens Class II; C111388:I-Ak antigen; D016056:Immunodominant Epitopes; D010446:Peptide Fragments; C045084:invariant chain; C066759:hen egg lysozyme peptide (46-61); D009113:Muramidase