title: Differential effects of γc cytokines on postselection differentiation of CD8 thymocytes.
abstract: The primary consequence of positive selection is to render thymocytes responsive to cytokines and chemokines expressed in the thymic medulla. In the present study, our main objective was to discover which cytokines could support the differentiation of positively selected thymocytes. To this end, we have developed an in vitro model suitable for high-throughput analyses of positive selection and CD8 T-cell differentiation. The model involves coculture of TCR(hi)CD5(int)CD69(-) double-positive (DP) thymocytes with peptide-pulsed OP9 cells and γc-cytokines. We report that IL-4, IL-7, and IL-21 have nonredundant effects on positively selected DP thymocytes. IL-7 signaling phosphorylates STAT5 and ERK; induces Foxo1, Klf2, and S1pr1; and supports the differentiation of classic CD8 T cells. IL-4 activates STAT6 and ERK and supports the differentiation of CD8(int)PD-L1(hi)CD44(hi)EOMES(+) innate CD8 T cells. IL-21 is produced by thymic epithelial cells and the IL-21 receptor-α is strongly induced on DP thymocytes undergoing positive selection. IL-21 signaling phosphorylates STAT3 and STAT5, but not ERK, and does not support CD8 T-cell differentiation. However, IL-21 has a unique ability to up-regulate BCL-6, expand DP thymocytes undergoing positive selection, and increase the production of mature T cells. Our data suggest that injection of recombinant IL-21 might enhance thymic output in subjects with age- or disease-related thymic atrophy.
authors.affiliation: Institute for Research in Immunology and Cancer, Université de Montréal, Montreal, QC, Canada.
authors.forename: Moutih
authors.initials: M
authors.lastname: Rafei
authors.forename: Alexandre
authors.initials: A
authors.lastname: Rouette
authors.forename: Sylvie
authors.initials: S
authors.lastname: Brochu
authors.forename: Juan Ruiz
authors.initials: JR
authors.lastname: Vanegas
authors.forename: Claude
authors.initials: C
authors.lastname: Perreault
mesh_terms: D000818:Animals; D001284:Atrophy; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects; D060966:Clonal Selection, Antigen-Mediated / Q000187:drug effects*; D018920:Coculture Techniques; D016207:Cytokines / Q000494:pharmacology / Q000502:physiology*; D004847:Epithelial Cells / Q000378:metabolism; D057166:High-Throughput Screening Assays; D007121:Immunocompetence / Q000187:drug effects; D053631:Interleukin Receptor Common gamma Subunit / Q000187:drug effects* / Q000502:physiology; D038041:Lymphopoiesis / Q000187:drug effects*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000494:pharmacology; D050791:STAT Transcription Factors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013047:Specific Pathogen-Free Organisms; D013601:T-Lymphocytes / Q000166:cytology*; D060168:Thymocytes / Q000166:cytology*; D013950:Thymus Gland / Q000166:cytology* / Q000187:drug effects / Q000276:immunology / Q000473:pathology
chemical_list: D016207:Cytokines; D053631:Interleukin Receptor Common gamma Subunit; D011994:Recombinant Proteins; D050791:STAT Transcription Factors