title: Myelin-reactive, TGF-β-induced regulatory T cells can be programmed to develop Th1-like effector function but remain less proinflammatory than myelin-reactive Th1 effectors and can suppress pathogenic T cell clonal expansion in vivo.
abstract: Interest in the use of regulatory T cells (Tregs) as cellular therapeutics has been tempered by reports of naturally occurring Tregs losing Foxp3 expression and producing IL-17, raising concerns over a switch to pathogenic function under inflammatory conditions in vivo. TGF-β-induced Tregs (inducible Tregs [iTregs]), generated in large numbers in response to disease-relevant Ags, represent the most amenable source of therapeutic Tregs. Using Foxp3-reporter T cells recognizing myelin basic protein (MBP), we investigated the capacity of iTregs to produce effector-associated cytokines under proinflammatory cytokine conditions in vitro and whether this translated into proinflammatory function in vivo. In contrast with naturally occurring Tregs, iTregs resisted conversion to an IL-17-producing phenotype but were able to express T-bet and to produce IFN-γ. iTregs initiated their T-bet expression during their in vitro induction, and this was dependent on exposure to IFN-γ. IL-12 reignited iTreg expression of T-bet and further promoted iTreg production of IFN-γ upon secondary stimulation. Despite losing Foxp3 expression and expressing both T-bet and IFN-γ, MBP-responsive IL-12-conditioned iTregs induced only mild CNS inflammation and only when given in high numbers. Furthermore, iTregs retained an ability to suppress naive T cell clonal expansion in vivo and protected against the development of experimental autoimmune encephalomyelitis. Therefore, despite bearing predictive hallmarks of pathogenic effector function, previously Foxp3(+) iTregs have much lower proinflammatory potential than that of MBP-responsive Th1 cells. Our results demonstrate that autoprotective versus autoaggressive functions in iTregs are not simply a binary relationship to be determined by their relative expression of Foxp3 versus T-bet and IFN-γ.
authors.affiliation: Medical Research Council, Centre for Inflammation Research, University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom.
authors.forename: Richard A
authors.initials: RA
authors.lastname: O'Connor
authors.forename: Melanie D
authors.initials: MD
authors.lastname: Leech
authors.forename: Janine
authors.initials: J
authors.lastname: Suffner
authors.forename: Günter J
authors.initials: GJ
authors.lastname: Hämmerling
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Anderton
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D016207:Cytokines / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D051858:Forkhead Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D051379:Mice; D018345:Mice, Knockout; D004676:Myelin Basic Protein / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D018417:Th1 Cells / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D016212:Transforming Growth Factor beta / Q000276:immunology* / Q000378:metabolism
chemical_list: D016207:Cytokines; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D004676:Myelin Basic Protein; D016212:Transforming Growth Factor beta