title: Generation of human CD8 T regulatory cells by CD40 ligand-activated plasmacytoid dendritic cells.
abstract: Although CD8 T cell-mediated immunosuppression has been a well-known phenomenon during the last three decades, the nature of primary CD8 T suppressor cells and the mechanism underlying their generation remain enigmatic. We demonstrated that naive CD8 T cells primed with allogeneic CD40 ligand-activated plasmacytoid dendritic cells (DC)2 differentiated into CD8 T cells that displayed poor secondary proliferative and cytolytic responses. By contrast, naive CD8 T cells primed with allogeneic CD40 ligand-activated monocyte-derived DCs (DC1) differentiated into CD8 T cells, which proliferated to secondary stimulation and killed allogeneic target cells. Unlike DC1-primed CD8 T cells that produced large amounts of interferon (IFN)-gamma upon restimulation, DC2-primed CD8 T cells produced significant amounts of interleukin (IL)-10, low IFN-gamma, and no IL-4, IL-5, nor transforming growth factor (TGF)-beta. The addition of anti-IL-10-neutralizing monoclonal antibodies during DC2 and CD8 T cell coculture, completely blocked the generation of IL-10-producing anergic CD8 T cells. IL-10-producing CD8 T cells strongly inhibit the allospecific proliferation of naive CD8 T cells to monocytes, and mature and immature DCs. This inhibition was mediated by IL-10, but not by TGF-beta. IL-10-producing CD8 T cells could inhibit the bystander proliferation of naive CD8 T cells, provided that they were restimulated nearby to produce IL-10. IL-10-producing CD8 T cells could not inhibit the proliferation of DC1-preactivated effector T cells. This study demonstrates that IL-10-producing CD8 T cells are regulatory T cells, which provides a cellular basis for the phenomenon of CD8 T cell-mediated immunosuppression and suggests a role for plasmacytoid DC2 in immunological tolerance.
authors.affiliation: Department of Immunology, DNAX Research Institute of Molecular and Cellular Biology, 901 California Avenue, Palo Alto, CA 94304, USA.
authors.forename: Michel
authors.initials: M
authors.lastname: Gilliet
authors.forename: Yong-Jun
authors.initials: YJ
authors.lastname: Liu
mesh_terms: D023201:CD40 Ligand / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D002450:Cell Communication / Q000276:immunology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007165:Immunosuppression Therapy; D007371:Interferon-gamma / Q000276:immunology; D016753:Interleukin-10 / Q000276:immunology; D015847:Interleukin-4 / Q000276:immunology; D015848:Interleukin-5 / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000276:immunology
chemical_list: D015848:Interleukin-5; D016212:Transforming Growth Factor beta; D016753:Interleukin-10; D023201:CD40 Ligand; D015847:Interleukin-4; D007371:Interferon-gamma