%0 Journal Article %J Nat Immunol %D 2009 %T The costimulatory molecule ICOS regulates the expression of c-Maf and IL-21 in the development of follicular T helper cells and TH-17 cells. %A Bauquet, Aurelie T %A Jin, Hulin %A Paterson, Alison M %A Mitsdoerffer, Meike %A Ho, I-Cheng %A Sharpe, Arlene H %A Kuchroo, Vijay K %K Animals %K Antigens, Differentiation, T-Lymphocyte %K Cell Differentiation %K Cell Proliferation %K Encephalomyelitis, Autoimmune, Experimental %K Enzyme-Linked Immunosorbent Assay %K Flow Cytometry %K Gene Expression Regulation %K Inducible T-Cell Co-Stimulator Protein %K Interleukin-17 %K Interleukins %K Mice %K Mice, Transgenic %K Oligonucleotide Array Sequence Analysis %K Proto-Oncogene Proteins c-maf %K Reverse Transcriptase Polymerase Chain Reaction %K T-Lymphocyte Subsets %K T-Lymphocytes, Helper-Inducer %X The inducible costimulatory molecule ICOS has been suggested to be important in the development of interleukin 17 (IL-17)-producing helper T cells (T(H)-17 cells) and of follicular helper T cells (T(FH) cells). Here we show that ICOS-deficient mice had no defect in T(H)-17 differentiation but had fewer T(H)-17 cells after IL-23 stimulation and fewer T(FH) cells. We also show that T(FH) cells produced IL-17 and that T(FH) cells in ICOS-deficient mice were defective in IL-17 production. Both T(H)-17 and T(FH) cells had higher expression of the transcription factor c-Maf. Genetic loss of c-Maf resulted in a defect in IL-21 production and fewer T(H)-17 and T(FH) cells. Thus our data suggest that ICOS-induced c-Maf regulates IL-21 production that in turn regulates the expansion of T(H)-17 and T(FH) cells. %B Nat Immunol %V 10 %P 167-75 %8 2009 Feb %G eng %N 2 %1 http://www.ncbi.nlm.nih.gov/pubmed/19098919?dopt=Abstract %R 10.1038/ni.1690