title: Direct stimulation of naïve T cells by antigen-presenting cell vesicles.
abstract: T cells are activated through T cell receptor (TCR) recognition of peptidic fragments of antigen bound to major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC). In addition, T cells require a costimulatory signal delivered through contact with other ligands on APC, especially B7 and ICAM-1 which bind to CD28 and LFA-1, respectively, on T cells. Under physiological conditions, T cell activation requires contact with viable APC. Under defined conditions, however, T cells can be activated by exosomes secreted by APC. Evidence will be presented that exosomes can be directly immunogenic for CD8(+) T cells in the absence of normal APC with the proviso that exosomes express a high density of MHC I/peptide complexes as well as B7 and ICAM-1. Similar findings apply to plasma membrane fragments prepared from APC sonicates.
authors.affiliation: Department of Immunology, IMM4, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA. jsprent@scripps.edu
authors.forename: Jonathan
authors.initials: J
authors.lastname: Sprent
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000938:Antigen-Presenting Cells / Q000378:metabolism; D018122:B7-1 Antigen / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology
chemical_list: D018122:B7-1 Antigen; D015395:Histocompatibility Antigens Class I; D018799:Intercellular Adhesion Molecule-1