IL-2, -7, and -15, but not thymic stromal lymphopoeitin, redundantly govern CD4+Foxp3+ regulatory T cell development.

Center for Immunology and Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA.
The Journal of Immunology (Impact Factor: 5.36). 10/2008; 181(5):3285-90. DOI: 10.4049/jimmunol.181.5.3285
Source: PubMed

ABSTRACT Common gamma chain (gammac)-receptor dependent cytokines are required for regulatory T cell (Treg) development as gammac(-/-) mice lack Tregs. However, it is unclear which gammac-dependent cytokines are involved in this process. Furthermore, thymic stromal lymphopoietin (TSLP) has also been suggested to play a role in Treg development. In this study, we demonstrate that developing CD4(+)Foxp3(+) Tregs in the thymus express the IL-2Rbeta, IL-4Ralpha, IL-7Ralpha, IL-15Ralpha, and IL-21Ralpha chains, but not the IL9Ralpha or TSLPRalpha chains. Moreover, only IL-2, and to a much lesser degree IL-7 and IL-15, were capable of transducing signals in CD4(+)Foxp3(+) Tregs as determined by monitoring STAT5 phosphorylation. Likewise, IL-2, IL-7, and IL-15, but not TSLP, were capable of inducing the conversion of CD4(+)CD25(+)Foxp3(-) thymic Treg progenitors into CD4(+)Foxp3(+) mature Tregs in vitro. To examine this issue in more detail, we generated IL-2Rbeta(-/-) x IL-7Ralpha(-/-) and IL-2Rbeta(-/-) x IL-4Ralpha(-/-) mice. We found that IL-2Rbeta(-/-) x IL-7Ralpha(-/-) mice were devoid of Tregs thereby recapitulating the phenotype observed in gammac(-/-) mice; in contrast, the phenotype observed in IL-2Rbeta(-/-) x IL-4Ralpha(-/-) mice was comparable to that seen in IL-2Rbeta(-/-) mice. Finally, we observed that Tregs from both IL-2(-/-) and IL-2Rbeta(-/-) mice show elevated expression of IL-7Ralpha and IL-15Ralpha chains. Addition of IL-2 to Tregs from IL-2(-/-) mice led to rapid down-regulation of these receptors. Taken together, our results demonstrate that IL-2 plays the predominant role in Treg development, but that in its absence the IL-7Ralpha and IL-15Ralpha chains are up-regulated and allow for IL-7 and IL-15 to partially compensate for loss of IL-2.

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    ABSTRACT: The developmental pathways of regulatory T cells (Treg) generation in the thymus are not fully understood. In this study, we reconstituted thymic development of Zap70-deficient thymocytes with a tetracycline-inducible Zap70 transgene to allow temporal dissection of Treg development. We find that Treg develop with distinctive kinetics, first appearing by day 4 among CD4 single-positive (SP) thymocytes. Accepted models of CD25(+)Foxp3(+) Treg selection suggest development via CD25(+)Foxp3(-) CD4 SP precursors. In contrast, our kinetic analysis revealed the presence of abundant CD25(-)Foxp3(+) cells that are highly efficient at maturing to CD25(+)Foxp3(+) cells in response to IL-2. CD25(-)Foxp3(+) cells more closely resembled mature Treg both with respect to kinetics of development and avidity for self-peptide MHC. These population also exhibited distinct requirements for cytokines during their development. CD25(-)Foxp3(+) cells were IL-15 dependent, whereas generation of CD25(+)Foxp3(+) specifically required IL-2. Finally, we found that IL-2 and IL-15 arose from distinct sources in vivo. IL-15 was of stromal origin, whereas IL-2 was of exclusively from hemopoetic cells that depended on intact CD4 lineage development but not either Ag-experienced or NKT cells.
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    ABSTRACT: The dynamic interplay between regulatory T cells (Tregs) and effector T cells (Teffs) governs the balance between tolerance and effector immune responses. Perturbations of Treg frequency and function or imbalances in Treg/Teff levels are associated with the development of autoimmunity. The factors that mediate these changes remain poorly understood and were investigated in this study in murine autoimmune arthritis. Tregs displayed a stable phenotype in arthritic mice and were fully functional in in vitro suppression assays. However, their expansion was delayed relative to Teffs (T follicular helper cells and Th17 cells) during the early stages of autoimmune reactivity. This imbalance is likely to have led to insufficient Treg control of Teffs and induced autoimmunity. Moreover, a counterregulatory and probably IL-7-driven increase in thymic Treg production and recruitment to inflamed tissues was too slow for disease prevention. Increased Teff over Treg expansion was further aggravated by inflammation and lymphopenia. Both these conditions contribute to autoimmune pathogenesis and were accompanied by decreases in the availability of IL-2 and increases in levels of IL-21. IL-2 neutralization or supplementation was used to show that Treg expansion mainly depended on this cytokine. IL-21R(-/-) cells were used to demonstrate that IL-21 promoted the maintenance of Teffs. Thus, at inflammatory sites in experimental arthritis, a deficit in IL-2 hampers Treg proliferation, whereas exaggerated IL-21 levels overwhelm Treg control by supporting Teff expansion. This identifies IL-2 and IL-21 as targets for manipulation in therapies for autoimmunity.
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    ABSTRACT: E-proteins are TCR-sensitive transcription factors essential for intrathymic T cell transitions. Here, we show that deletion of E-proteins leads to both enhanced peripheral TGF-β-induced regulatory T (iT reg) cell and thymic naturally arising T reg cell (nT reg cell) differentiation. In contrast, deletion of Id proteins results in reduced nT reg cell differentiation. Mechanistic analysis indicated that decreased E-protein activity leads to de-repression of signaling pathways that are essential to Foxp3 expression. Decreased E-protein binding to an IL-2Rα enhancer locus facilitated TCR-induced IL-2Rα expression. Similarly, decreased E-protein activity facilitated TCR-induced NF-κB activation and generation of c-Rel. Consistent with this, microarray analysis indicated that cells with E-protein depletion that are not yet expressing Foxp3 exhibit activation of the IL-2 and NF-κB signaling pathways as well as enhanced expression of many of the genes associated with Foxp3 induction. Finally, studies using Nur77-GFP mice to monitor TCR signaling showed that TCR signaling strength sufficient to induce Foxp3 differentiation is accompanied by down-regulation of E-protein levels. Collectively, these data suggest that TCR stimulation acts in part through down-regulation of E-protein activity to induce T reg cell lineage development. © 2014 Gao et al.
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