title: CD4(+) T cell-released exosomes inhibit CD8(+) cytotoxic T-lymphocyte responses and antitumor immunity.
abstract: T cells secrete bioactive exosomes (EXO), but the potential immunoregulatory effect of T-cell EXO is largely unknown. In this study, we generated activated ovalbumin (OVA)-specific CD4(+) T cells in vitro via coculture of OVA-pulsed dendritic cells (DC(OVA)) with naive CD4(+) T cells derived from OVA-specific T-cell receptor (TCR) transgenic OTII mice. CD4(+) T-cell EXO were then purified from the CD4(+) T-cell culture supernatants by differential ultracentrifugation. CD4(+) T-cell EXO exhibited the 'saucer' shape that is characteristic of EXO with a diameter between 50 and 100 nm, as assessed by electron microscopy, and contained the EXO-associated proteins LAMP-1, TCR and lymphocyte function associated antigen-1 (LFA-1), as determined by western blot. Flow cytometric analysis showed that CD4(+) T-cell EXO expressed CD4(+) T-cell markers (CD4, TCR, LFA-1, CD25 and Fas ligand), but to a lesser extent than CD4(+) T cells. We demonstrated that DC(OVA) took up CD4(+) T-cell EXO via peptide/major histocompatibility complex (pMHC) II/TCR and CD54/LFA-1 interactions. OVA-specific CD4(+) T-cell EXO from OTII mice, but not ConA-stimulated polyclonal CD4(+) T-cell EXO from wild-type C57BL/6 mice inhibited DC(OVA)-stimulated in vitro CD4(+) T-cell proliferation and in vivo CD8(+) cytotoxic T lymphocyte (CTL) responses and antitumor immunity against OVA-expressing B16 melanoma BL6-10(OVA) cells. In addition, EXO derived from a T-cell hybridoma cell line, MF72.2D9, expressing an OVA-specific CD4(+) TCR, had a similar inhibitory effect as OTII CD4(+) T-cell EXO on CTL-mediated antitumor immunity. Taken together, our data indicate that antigen-specific T-cell EXO may serve as a new type of immunosuppressive reagent for use in transplant rejection and treatment of autoimmune diseases.
authors.affiliation: Research Unit, Health Research Division, Saskatchewan Cancer Agency, Department of Oncology and Immunology, University of Saskatchewan, Saskatoon, Sask., Canada.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Zhang
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Xie
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Rajni
authors.initials: R
authors.lastname: Chibbar
authors.forename: Sidong
authors.initials: S
authors.lastname: Xiong
authors.forename: Jim
authors.initials: J
authors.lastname: Xiang
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000517:prevention & control; D015415:Biomarkers; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic; D003713:Dendritic Cells / Q000276:immunology; D055354:Exosomes / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D006084:Graft Rejection / Q000517:prevention & control; D007109:Immunity; D056747:Immunomodulation; D008213:Lymphocyte Activation / Q000276:immunology; D008546:Melanoma, Experimental / Q000188:drug therapy / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009368:Neoplasm Transplantation / Q000276:immunology; D010047:Ovalbumin / Q000276:immunology / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000276:immunology
chemical_list: D015415:Biomarkers; D010047:Ovalbumin