IRF4 is essential for IL-21-mediated induction, amplification, and stabilization of the Th17 phenotype.
Differentiation of murine T-helper (Th) 17 cells is induced by antigenic stimulation and the sequential action of the cytokines IL-6, IL-21, and IL-23, along with TGFbeta. Current dogma proposes that IL-6 induces IL-21, which, in a STAT3-dependent manner, amplifies its own transcription, contributes to IL-17 production, and, moreover, promotes the expression of the IL-23 receptor. This, in turn, prepares cells for IL-23-mediated stabilization of the Th17 phenotype. Here we demonstrate that these effects of IL-21 on Th17 differentiation are completely dependent on IFN regulatory factor 4 (IRF4). After culturing in the presence of IL-21 plus TGFbeta, IRF4-deficient (Irf4(-/-)) Th cells showed a profound intrinsic defect in IL-17 production and in the autocrine IL-21 loop. Likewise, the levels of IL-23 receptor and the lineage-specific orphan nuclear receptors RORalpha and RORgammat were diminished, whereas the T regulatory (Treg) transcription factor forkhead box P3 (Foxp3) was strongly up-regulated, consistent with the reciprocal relationship between Th17 and Treg development. Despite this loss of IL-21 functions, IL-21-induced STAT3 activation was unimpaired and induced normal Socs3 expression. Forced expression of Foxp3 in WT cells inhibited IL-21-mediated IL-17 production, suggesting that the increase in Foxp3 contributes to the Irf4(-/-) phenotype. Additionally, the low levels of RORalpha and RORgammat are also partially responsible, because simultaneous overexpression of both proteins restored IL-17 production in Irf4(-/-) cells to some extent. These data highlight IRF4 as a decisive factor during the IL-21-mediated steps of Th17 development by influencing the balance of Foxp3, RORalpha, and RORgammat.
Huber
Magdalena
M
Institut für Medizinische Mikrobiologie und Hygiene, Universität Marburg, 35043 Marburg, Germany. huberma@med.uni-marburg.de
Brüstle
Anne
A
Reinhard
Katharina
K
Guralnik
Anna
A
Walter
Gina
G
Mahiny
Azita
A
von Löw
Eberhard
E
Lohoff
Michael
M
D000818:Animals; D019898:Autocrine Communication / Q000276:immunology*; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000276:immunology; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000276:immunology; D050835:Interferon Regulatory Factors / Q000235:genetics / Q000276:immunology*; D007378:Interleukins / Q000235:genetics / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3; D010641:Phenotype; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000276:immunology; D018123:Receptors, Interleukin / Q000235:genetics / Q000276:immunology; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000276:immunology; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000276:immunology; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D015534:Trans-Activators / Q000235:genetics / Q000276:immunology; D015854:Up-Regulation / Q000276:immunology; D000098546:Interleukin-21; D000099218:Interferon Regulatory Factor-4
D016207:Cytokines; D051858:Forkhead Transcription Factors; D050835:Interferon Regulatory Factors; D007378:Interleukins; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3; D018160:Receptors, Cytoplasmic and Nuclear; D018123:Receptors, Interleukin; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D050796:STAT3 Transcription Factor; D015534:Trans-Activators; D000098546:Interleukin-21; D000099218:Interferon Regulatory Factor-4; C498833:Foxp3 protein, mouse; C539901:Rorc protein, mouse; C494087:Stat3 protein, mouse; C528688:interleukin-23 receptor, mouse