title: IL-21 initiates an alternative pathway to induce proinflammatory T(H)17 cells.
abstract: On activation, naive T cells differentiate into effector T-cell subsets with specific cytokine phenotypes and specialized effector functions. Recently a subset of T cells, distinct from T helper (T(H))1 and T(H)2 cells, producing interleukin (IL)-17 (T(H)17) was defined and seems to have a crucial role in mediating autoimmunity and inducing tissue inflammation. We and others have shown that transforming growth factor (TGF)-beta and IL-6 together induce the differentiation of T(H)17 cells, in which IL-6 has a pivotal function in dictating whether T cells differentiate into Foxp3+ regulatory T cells (T(reg) cells) or T(H)17 cells. Whereas TGF-beta induces Foxp3 and generates T(reg) cells, IL-6 inhibits the generation of T(reg) cells and induces the production of IL-17, suggesting a reciprocal developmental pathway for T(H)17 and T(reg) cells. Here we show that IL-6-deficient (Il6-/-) mice do not develop a T(H)17 response and their peripheral repertoire is dominated by Foxp3+ T(reg) cells. However, deletion of T(reg) cells leads to the reappearance of T(H)17 cells in Il6-/- mice, suggesting an additional pathway by which T(H)17 cells might be generated in vivo. We show that an IL-2 cytokine family member, IL-21, cooperates with TGF-beta to induce T(H)17 cells in naive Il6-/- T cells and that IL-21-receptor-deficient T cells are defective in generating a T(H)17 response.
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Korn
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Estelle
authors.initials: E
authors.lastname: Bettelli
authors.affiliation: Transplant Research Center, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Wenda
authors.initials: W
authors.lastname: Gao
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, 65 Landsdowne Street, Cambridge, Massachusetts 02139, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Awasthi
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Anneli
authors.initials: A
authors.lastname: Jäger
authors.affiliation: Transplant Research Center, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Terry B
authors.initials: TB
authors.lastname: Strom
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, 65 Landsdowne Street, Cambridge, Massachusetts 02139, USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Oukka
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Kuchroo
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000276:immunology; D051858:Forkhead Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000276:immunology; D015850:Interleukin-6 / Q000172:deficiency / Q000235:genetics; D007378:Interleukins / Q000172:deficiency / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018655:Lymphocyte Count; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D006377:T-Lymphocytes, Helper-Inducer / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000276:immunology / Q000378:metabolism; D000098546:Interleukin-21
chemical_list: D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D015850:Interleukin-6; D007378:Interleukins; D016212:Transforming Growth Factor beta; D000098546:Interleukin-21