title: Th17: the third member of the effector T cell trilogy.
abstract: T helper responses have now grown to include three T cell subsets: Th1, Th2 and Th17. Th17 cells have recently emerged as a third independent T cell subset that may play an essential role in protection against certain extracellular pathogens. However, Th17 cells with specificity for self-antigens are highly pathogenic and lead to the development of inflammation and severe autoimmunity. A combination of TGF-beta plus IL-6 and the transcription factors STAT3 and RORgammat were recently described to be essential for initial differentiation of Th17 cells and IL-23 for the later stabilization of the Th17 cell subset. Here, we introduce another player IL-21 produced by Th17 themselves, which plays an important role in the amplification of Th17 cells. Thus, Th17 cells may undergo three distinct steps of development: differentiation, amplification and stabilization in which distinct cytokines play a role.
authors.affiliation: Center for Neurologic Diseases, Brigham & Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Estelle
authors.initials: E
authors.lastname: Bettelli
authors.forename: Thomas
authors.initials: T
authors.lastname: Korn
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Kuchroo
mesh_terms: D000818:Animals; D015551:Autoimmunity; D002454:Cell Differentiation; D006801:Humans; D020381:Interleukin-17 / Q000276:immunology / Q000378:metabolism; D053759:Interleukin-23 / Q000276:immunology / Q000378:metabolism*; D015850:Interleukin-6 / Q000276:immunology / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000276:immunology / Q000378:metabolism; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000276:immunology / Q000378:metabolism
chemical_list: D020381:Interleukin-17; D053759:Interleukin-23; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; D016212:Transforming Growth Factor beta