Regulatory T cells (Tregsanergy ͉ Blimp-1 ͉ inflammatory bowel disease ͉ IL-10 ͉ type 1 regulatory T cells

No abstract

Autoantibodies induce various autoimmune diseases, including systemic lupus erythematosus (SLE). We previously described that CD4+CD25−LAG3+ regulatory T cells (LAG3+ Treg) are regulated by Egr2, a zinc-finger transcription factor required for the induction of T-cell anergy. We herein demonstrate that LAG3+ Treg produce high amounts of TGF-β3 in an Egr2- and Fas-dependent manner. LAG3+ Treg require TGF-β3 to suppress B-cell responses in a murine model of lupus. Moreover, TGF-β3- and LAG3+ Treg-mediated suppression requires PD-1 expression on B cells. We also show that TGF-β3-expressing human LAG3+ Treg suppress antibody production and that SLE patients exhibit decreased frequencies of LAG3+ Treg. These results clarify the mechanism of B-cell regulation and suggest therapeutic strategies.

Recent evidence suggests that a substantial portion of complex disease risk alleles modify gene expression in a cell-specific manner. To identify candidate causal genes and biological pathways of immune-related complex diseases, we conducted expression quantitative trait loci (eQTL) analysis on five subsets of immune cells (CD4 T cells, CD8 T cells, B cells, natural killer (NK) cells and monocytes) and unfractionated peripheral blood from 105 healthy Japanese volunteers. We developed a three-step analytical pipeline comprising (i) prediction of individual gene expression using our eQTL database and public epigenomic data, (ii) gene-level association analysis and (iii) prediction of cell-specific pathway activity by integrating the direction of eQTL effects. By applying this pipeline to rheumatoid arthritis data sets, we identified candidate causal genes and a cytokine pathway (upregulation of tumor necrosis factor (TNF) in CD4 T cells). Our approach is an efficient way to characterize the polygenic contributions and potential biological mechanisms of complex diseases.

Interleukin-27 (IL-27) suppresses immune responses through inhibition of the development of IL-17 producing Th17 cells and induction of IL-10 production.We previously showed that forced expression of early growth response gene 2 (Egr-2), a transcription factor required for T-cell anergy induction, induces IL-10 and lymphocyte activation gene 3 expression and confers regulatory activity on CD4 + T cells in vivo. Here, we evaluated the role of Egr-2 in IL-27-induced IL-10 production. Among various IL-10-inducing factors, only IL-27 induced high levels of Egr-2 and lymphocyte activation gene 3 expression. Intriguingly, IL-27 failed to induce IL-10 in Egr-2-deficient T cells. IL-27-mediated induction of Prdm1 that codes B lymphocyte induced maturation protein-1, a transcriptional regulator important for IL-10 production in CD4 + T cells, was also impaired in the absence of Egr-2. Although IL-27-mediated IL-10 induction was dependent on both STAT1 and STAT3, only STAT3 was required for IL-27-mediated Egr-2 induction. These results suggest that IL-27 signal transduction through Egr-2 and B lymphocyte induced maturation protein-1 plays an important role in IL-10 production. Furthermore, Egr-2-deficient CD4 + T cells showed dysregulated production of IFN-γ and IL-17 in response to IL-27 stimulation. Therefore, Egr-2 may play key roles in controlling the balance between regulatory and effector cytokines.Keywords: Blimp-1 r Egr-2 r IL-10 r IL-27 r inducible regulatory T (Treg) cells r Prdm1 See accompanying Commentary by Vasanthakumar and KalliesAdditional supporting information may be found in the online version of this article at the publisher's web-site [3,4]. IL-10 is an anti-inflammatory cytokine which was initially described as a cytokine associated with Th2 cells that inhibits the production of IFN-γ by Th1 cells [5,6]. A number of reports have revealed that IL-10 suppresses cytokine production and proliferation of T cells [7,8] and inhibits the T-cell-stimulating capacity of APCs [9]. IL-10-deficient mice die with spontaneously developed inflammatory bowel disease [10].Interleukin-27 (IL-27), a member of the IL-12/IL-23 heterodimeric family of cytokines produced by APCs, is composed of two chains, p28 and EBV-induced gene 3 [11]. IL-27 induces the expansion of Th1 cells by activating the STAT1-mediated T-bet pathway [12], but IL-27Rα-deficient mice developed severe EAE with enhanced Th17-cell responses [13]. The immunosuppressive effects of IL-27 depend on inhibition of the development of Th17 cells and induction of IL-10 production [14]. Recently, IL-27 has been identified as a differentiation factor for IL-10-producing Tr1 cells [15][16][17]. On the other hand, B lymphocyte induced maturation protein-1 (Blimp-1) (coded by Prdm1 gene), a zinc finger-containing transcriptional regulator that is well known to be a regulator of plasma cell differentiation, is also important for IL-10 production in naïve CD4 + T cells. Martins et al. [18,19] reported that Blimp-1-deficient CD4 + T cells proliferated more and produce...

Inhibitory cytokines, such as transforming growth factor-β (TGF-β) and interleukin-10 (IL-10), are humoral factors involved in the suppressive function of regulatory T cells and play critical roles in maintaining immune homeostasis. However, TGF-β and IL-10 also have pleiotropic effects and induce humoral immune responses depending on conditions, and thus their therapeutic application to autoimmune diseases remains limited. Here, we show that a combination of TGF-β and IL-10, but not single cytokine, is required to suppress B cell activation induced by toll-like receptor (TLR) stimulation. In in vivo analyses, the simultaneous presence of TGF-β and IL-10 effectively suppressed TLR-mediated antigen-specific immune responses and ameliorated pathologies in imiquimod (TLR7 agonist)-induced lupus model and lupus-prone MRL/lpr mice. Intriguingly, TGF-β and IL-10 synergistically modulated transcriptional programs and suppressed cellular energetics of both glycolysis and oxidative phosphorylation via inhibition of the mammalian target of rapamycin complex 1 (mTORC1)/S6 kinase 1 (S6K1) pathway in TLR-stimulated B cells. On the other hand, enhancement of mTOR signaling and mitochondrial biosynthesis in TLR-stimulated B cells counteracted the synergistic inhibitory effects. The inhibitory cytokine synergy of TGF-β and IL-10 via suppression of energy metabolism was also observed in human TLR-stimulated B cells. There is increasing evidence supporting the importance of adequate metabolic signals in various immune cells to exert their immune function. In this study, we have shown that a previously unrecognized synergy of inhibitory cytokines regulates systemic humoral immune responses via modulating immunometabolism in B cells. Our findings indicate that inhibition of B cell metabolism mediated by two synergistic cytokines contributes to the induction of immune tolerance and could be a new therapeutic strategy for autoimmune diseases such as systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease characterized by multiorgan inflammation induced by autoantibodies. Early growth response gene 2 (Egr2), a transcription factor essential for T-cell anergy induction, controls systemic autoimmunity in mice and humans. We have previously identified a subpopulation of CD4 + regulatory T cells, CD4+ cells, that characteristically express both Egr2 and LAG3 and control mice model of lupus via TGF-β3 production. However, due to the mild phenotype of lymphocyte-specific Egr2-deficient mice, the presence of an additional regulator has been speculated. Here, we show that Egr2 and Egr3 expressed in T cells cooperatively prevent humoral immune responses by supporting TGF-β3 secretion. T cell-specific Egr2/Egr3 double-deficient (Egr2/3DKO) mice spontaneously developed an early onset lupus-like disease that was more severe than in T cell-specific Egr2-deficient mice. In accordance with the observation that CD4+ cells from Egr2/3DKO mice completely lost the capacity to produce TGF-β3, the excessive germinal center reaction in Egr2/3DKO mice was suppressed by the adoptive transfer of WT CD4+ cells or treatment with a TGF-β3-expressing vector. Intriguingly, latent TGF-β binding protein (Ltbp)3 expression maintained by Egr2 and Egr3 was required for TGF-β3 production from CD4+ cells. Because Egr2 and Egr3 did not demonstrate cell intrinsic suppression of the development of follicular helper T cells, Egr2-and Egr3-dependent TGF-β3 production by CD4+ cells is critical for controlling excessive B-cell responses. The unique attributes of Egr2/Egr3 in T cells may provide an opportunity for developing novel therapeutics for autoantibodymediated diseases including SLE.Egr2 | Egr3 | TGF-β3 | systemic lupus erythematosus | regulatory T cell

IntroductionAnti-citrullinated protein/peptide antibodies (ACPAs) are highly specific to rheumatoid arthritis (RA) patients and are thought to have a close relationship with the pathogenesis of arthritis. Several proteins, including fibrinogen, vimentin, and alpha-enolase, were reported as ACPA-target antigens, and their importance in RA pathogenesis was widely proposed. We identified citrullinated immunoglobulin binding protein (citBiP) as another ACPA target in RA patients and examined its pro-inflammatory role in arthritis.MethodsWe measured the levels of anti-citBiP, anti-BiP, and anti-cyclic citrullinated peptide (CCP) antibodies in the serum of RA patients (n = 100), systemic lupus erythematosus (SLE) patients (n = 60), and healthy controls (n = 30) using ELISA and immunoblotting. Epitope mapping was performed using 27 citBiP-derived peptides. In the mouse study, after DBA/1J mice were immunized with BiP or citBiP, serum titers of ACPAs were measured by ELISA and immunohistochemistry. The development of collagen-induced arthritis (CIA) was observed in BiP- or citBiP-pre-immunized mice.ResultsThe serum levels of anti-BiP and anti-citBiP antibodies were significantly increased in RA patients, although only anti-BiP antibodies were slightly increased in SLE patients. Interestingly, anti-citBiP antibody levels were higher than anti-BiP antibody levels in 72% of RA patients, whereas no significant increase in anti-citBiP antibody levels was detected in SLE patients and healthy controls. The serum levels of anti-CCP antibodies were correlated with those of anti-citBiP antibodies in RA patients (R2 = 0.41). Several citrulline residues of citBiP were determined to be major epitopes of anti-citBiP antibodies, one of which showed cross-reactivity with CCP. Immunization of DBA/1J mice with citBiP induced several kinds of ACPAs, including anti-CCP and anti-citrullinated fibrinogen antibodies. Pre-immunization with citBiP exacerbated CIA, and anti-CCP antibody levels were increased in citBiP-pre-immunized CIA mice.ConclusionsCitBiP is a newly described ACPA target that may play a pro-inflammatory role in arthritis.