title: Direct expansion of functional CD25+ CD4+ regulatory T cells by antigen-processing dendritic cells.
abstract: An important pathway for immune tolerance is provided by thymic-derived CD25+ CD4+ T cells that suppress other CD25- autoimmune disease-inducing T cells. The antigen-presenting cell (APC) requirements for the control of CD25+ CD4+ suppressor T cells remain to be identified, hampering their study in experimental and clinical situations. CD25+ CD4+ T cells are classically anergic, unable to proliferate in response to mitogenic antibodies to the T cell receptor complex. We now find that CD25+ CD4+ T cells can proliferate in the absence of added cytokines in culture and in vivo when stimulated by antigen-loaded dendritic cells (DCs), especially mature DCs. With high doses of DCs in culture, CD25+ CD4+ and CD25- CD4+ populations initially proliferate to a comparable extent. With current methods, one third of the antigen-reactive T cell receptor transgenic T cells enter into cycle for an average of three divisions in 3 d. The expansion of CD25+ CD4+ T cells stops by day 5, in the absence or presence of exogenous interleukin (IL)-2, whereas CD25- CD4+ T cells continue to grow. CD25+ CD4+ T cell growth requires DC-T cell contact and is partially dependent upon the production of small amounts of IL-2 by the T cells and B7 costimulation by the DCs. After antigen-specific expansion, the CD25+ CD4+ T cells retain their known surface features and actively suppress CD25- CD4+ T cell proliferation to splenic APCs. DCs also can expand CD25+ CD4+ T cells in the absence of specific antigen but in the presence of exogenous IL-2. In vivo, both steady state and mature antigen-processing DCs induce proliferation of adoptively transferred CD25+ CD4+ T cells. The capacity to expand CD25+ CD4+ T cells provides DCs with an additional mechanism to regulate autoimmunity and other immune responses.
authors.affiliation: Laboratory of Cellular Physiology and Immunology, The Rockefeller University, New York, NY 10021, USA.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Tomonori
authors.initials: T
authors.lastname: Iyoda
authors.forename: Kristin
authors.initials: K
authors.lastname: Tarbell
authors.forename: Kara
authors.initials: K
authors.lastname: Olson
authors.forename: Klara
authors.initials: K
authors.lastname: Velinzon
authors.forename: Kayo
authors.initials: K
authors.lastname: Inaba
authors.forename: Ralph M
authors.initials: RM
authors.lastname: Steinman
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002455:Cell Division; D017635:Clonal Anergy / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D006801:Humans; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D015375:Receptors, Interleukin-2 / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*
chemical_list: D000949:Histocompatibility Antigens Class II; D015375:Receptors, Interleukin-2