Exogenous IL-2 Research Articles

High CD123 levels enhance proliferation in response to IL-3, but reduce chemotaxis by downregulating CXCR4 expression.

High expression of the α chain of the interleukin-3 receptor (IL-3Rα; CD123) is a hallmark of acute myeloid leukemia (AML) leukemic stem cells (LSCs). Elevated CD123 expression is part of the diagnostic immunophenotyping of myeloid leukemia, and higher expression is associated with poor prognosis. However, the biological basis of the poorer prognosis is unclear, and may include heightened IL-3 signaling and non-cell autonomous interactions with the bone marrow (BM) microenvironment. We used TF-1 cells expressing different levels of CD123 and found elevated CD123 levels amplified the proliferative response to exogenous IL-3 and maintained viability in reducing IL-3 concentrations. This was associated with stronger activation of STAT5, Akt, and extracellular signal-regulated kinase 1/2 in vitro. Surprisingly, in vivo e14.5 fetal liver cells transduced with retroviral constructs to express high CD123 failed to engraft in syngeneic recipients. In exploring the underlying mechanism for this, we found that CXCR4, a key molecule involved in LSC/BM interactions, was specifically downregulated in CD123 overexpressing cells in a manner dependent on IL-3 signaling. CXCR4 downregulation was sufficient to alter the chemotactic response of hematopoietic cells to stromal derived factor-1 (SDF-1). Thus, we propose that the overexpression of CD123 in AML LSC dictates their location by altering CXCR4/SDF-1 interaction in the BM, raising the possibility that this mechanism underpins the egress of BM AML LSC and more mature cells into the circulation.

Cutting Edge: Defective Aerobic Glycolysis Defines the Distinct Effector Function in Antigen-Activated CD8+ Recent Thymic Emigrants.

Recent thymic emigrants (RTEs) are the youngest peripheral T cells that have completed thymic selection and egress to the lymphoid periphery. RTEs are functionally distinct from their more mature but still naive T cell counterparts, because they exhibit dampened proliferation and reduced cytokine production upon activation. In this article, we show that, compared with more mature but still naive T cells, RTEs are impaired in their ability to perform aerobic glycolysis following activation. Impaired metabolism underlies the reduced IFN-γ production observed in activated RTEs. This failure to undergo Ag-induced aerobic glycolysis is caused by reduced mTORC1 activity and diminished Myc induction in RTEs. Critically, exogenous IL-2 restores Myc expression in RTEs, driving aerobic glycolysis and IFN-γ production to the level of mature T cells. These results reveal a previously unknown metabolic component to postthymic T cell maturation.

IL-2 therapy restores regulatory T-cell dysfunction induced by calcineurin inhibitors

CD4+CD25+FOXP3+ Tregs constitute a heterogeneous lymphocyte subpopulation essential for curtailing effector T cells and establishing peripheral tolerance. Calcineurin inhibitors (CNIs) are among the most effective agents in controlling effector T-cell responses in humans. However, CNIs also reduce the size of the Treg pool. The functional consequences of this negative effect and the mechanisms responsible remain to be elucidated. We report here that CNIs compromise the overall Treg immunoregulatory capacity to a greater extent than would be predicted by the reduction in the size of the Treg compartment, given that they selectively promote the apoptosis of the resting and activated Treg subsets that are known to display the most powerful suppressive function. These effects are caused by reduced access to IL-2, because Tregs remain capable of translocating NFAT even in the presence of high CNI levels. Exogenous IL-2 restores the phenotypic changes and overall gene-expression effects exerted by CNIs and can even promote Treg expansion by enhancing antiapoptotic Bcl-2 expression. In a skin transplant model, the addition of IL-2 synergizes with CNIs treatment, promoting intragraft accumulation of Tregs and prolonged allograft survival. Hence, the combination of IL-2 and CNIs constitutes an optimal immunomodulatory regimen that enhances the pool of suppressive Treg subsets while effectively controlling cytopathic T cells.

Interleukin-25 Produced by Synoviocytes Has Anti-inflammatory Effects by Acting As a Receptor Antagonist for Interleukin-17A Function.

The production and function of cytokines are highly regulated. One mechanism is the balance between pro- and anti-inflammatory cytokines. As interleukin (IL)-17A and IL-25 share the IL-17RA receptor chain, we hypothesize that IL-25 acts as an IL-17A receptor antagonist and limits its pro-inflammatory effects. The production and expression kinetics of IL-25 and its receptor chains IL-17RA and RB were analyzed in rheumatoid synoviocytes alone or in coculture with peripheral blood mononuclear cells (PBMCs). The effects of autocrine or exogenous IL-25 on synoviocytes were investigated in the presence or not of an anti-IL-25 antibody. To study the regulatory effects of IL-25, synoviocytes and/or PBMCs were exposed to IL-25 before being treated with IL-17A and tumor necrosis factor alpha (TNF-α) alone or combined. IL-25, IL-6, and bioactive IL-17A were quantified in rheumatoid arthritis (RA) patient plasma. Synoviocytes expressed and secreted IL-25, and expressed the two chains of its receptor IL-17RA and IL-17RB. IL-17RB expression was increased by TNF-α. IL-25 production occurred at a delayed time point (5 days) after stimulation with IL-17A and TNF-α. Synoviocytes pretreated with IL-25 were less responsive to IL-17A and TNF-α. PBMCs exposed to IL-25 showed a decreased production of pro-inflammatory mediators, including IL-17A with a 57% decrease; p = 0.002. IL-25 levels were elevated in the plasma of RA patients compared to healthy subjects (p = 0.03). However, these levels are not high enough to inhibit the function of circulating IL-17A. In conclusion, it was shown for the first time that synoviocytes produce IL-25, specifically at late time points and that IL-25 acts as a regulator of IL-17A-driven inflammation, as indicated by in vitro results and in vivo, in a long-term RA patient follow-up. These results may be important when considering IL-17A inhibition.

Dual-specific Chimeric Antigen Receptor T Cells and an Indirect Vaccine Eradicate a Variety of Large Solid Tumors in an Immunocompetent, Self-antigen Setting.

Purpose: While adoptive transfer of T cells bearing a chimeric antigen receptor (CAR) can eliminate substantial burdens of some leukemias, the ultimate challenge remains the eradication of large solid tumors for most cancers. We aimed to develop an immunotherapy approach effective against large tumors in an immunocompetent, self-antigen preclinical mouse model.Experimental Design: In this study, we generated dual-specific T cells expressing both a CAR specific for Her2 and a TCR specific for the melanocyte protein (gp100). We used a regimen of adoptive cell transfer incorporating vaccination (ACTIV), with recombinant vaccinia virus expressing gp100, to treat a range of tumors including orthotopic breast tumors and large liver tumors.Results: ACTIV therapy induced durable complete remission of a variety of Her2+ tumors, some in excess of 150 mm2, in immunocompetent mice expressing Her2 in normal tissues, including the breast and brain. Vaccinia virus induced extensive proliferation of T cells, leading to massive infiltration of T cells into tumors. Durable tumor responses required the chemokine receptor CXCR3 and exogenous IL2, but were independent of IFNγ. Mice were resistant to tumor rechallenge, indicating immune memory involving epitope spreading. Evidence of limited neurologic toxicity was observed, associated with infiltration of cerebellum by T cells, but was only transient.Conclusions: This study supports a view that it is possible to design a highly effective combination immunotherapy for solid cancers, with acceptable transient toxicity, even when the target antigen is also expressed in vital tissues. Clin Cancer Res; 23(10); 2478-90. ©2016 AACR.

Interleukin-18 gene deletion protects against sepsis-induced cardiac dysfunction by inhibiting PP2A activity

BackgroundInterleukin-18 (IL-18) neutralization protects against lipopolysaccharide (LPS)-induced injuries, including myocardial dysfunction. However, the mechanism is yet to be fully elucidated. The aim of the present study was to determine whether IL-18 gene deletion prevents sepsis-induced cardiac dysfunction and to elucidate the potential mechanisms underlying IL-18-mediated cardiotoxicity by LPS. Methods and resultsTen-week-old male wild-type (WT) and IL-18 knockout (IL-18 KO) mice were intraperitoneally administered LPS. Serial echocardiography showed better systolic pump function and less left ventricular (LV) dilatation in LPS-treated IL-18 KO mice compared with those in LPS-treated WT mice. LPS treatment significantly decreased the levels of phospholamban (PLN) and Akt phosphorylation in WT mice compared with those in saline-treated WT mice, while the LPS-induced decrease in the phosphorylation levels was attenuated in IL-18 KO mice compared with that in WT mice. IL-18 gene deletion also attenuated an LPS-induced increase of type 2 protein phosphatase 2A (PP2A) activity, a molecule that dephosphorylates PLN and Akt. There was no difference in type 1 protein phosphatase (PP1) activity. To address whether IL-18 affects PLN and Akt phosphorylation via PP2A activation in cardiomyocytes, rat neonatal cardiac myocytes were cultured and stimulated using 100ng/ml of recombinant rat IL-18. Exogenous IL-18 decreased the level of PLN and Akt phosphorylation in cardiomyocytes. PP2A activity but not PP1 activity was increased by IL-18 stimulation in cardiomyocytes. ConclusionsIL-18 plays a pivotal role in advancing sepsis-induced cardiac dysfunction, and the mechanisms underlying IL-18-mediated cardiotoxicity potentially involve the regulation of PLN and Akt phosphorylation through PP2A activity.

Sterile type 2 inflammation triggered by microparticles is abrogated by inhibition of IL33 through blockade of Bruton’s tyrosine kinase

Abstract Wear debris microparticle release associated with total joint arthroplasty may contribute to harmful inflammation, osteolysis and implant failure. We examined the role of different molecular signaling pathways in microparticle-mediated inflammation. Intraperitoneal inoculation of cobalt chrome (CoCr) in mice induced a robust innate type 2 response with increases in IL4, IL5, IL13, IL33, M2 macrophages, eosinophils and neutrophils compared to controls given vehicle only. Blockade of the SYK signaling pathway with the inhibitor BAY 61-3606 or the down stream BTK signaling pathway with Ibrutinib abrogated the CoCr-mediated innate type 2 inflammation. Further studies in CBA/Nxid mice, a genetic BTK loss of function mutant also showed decreases in type 2 inflammation, confirming a critical role for BTK in CoCr mediated sterile type 2 inflammation. Inoculation of JH−/−, B cell deficient mice, or depletion of T cells by anti-CD4 (GK1.5) antibody, had no impact on CoCr mediated type 2 inflammation. We further demonstrated that the major source of IL33 was macrophages and intra-peritoneal administration of recombinant IL33 rescued the CoCr mediated type 2 response after BTK blockade. These studies indicate that the type 2 immune response caused by solid particles is abrogated by blockade of BTK signaling pathways and that exogenous IL33 is sufficient to rescue this response. These studies elucidate the nature of wear debris-mediated type 2 sterile inflammation and provide potential targets for future therapy.

Critical role for OX40 signaling in Thymic and Peripheral Treg Expansion

Abstract Regulatory T-cells (Treg) play a pivotal role in suppressing self-reactive effector T-cells (Teff) and help maintain the critical balance between self-tolerance and autoimmunity. Restoration of homeostatic balance between Teff/Treg cells has been shown to ameliorate many autoimmune diseases including type-1 diabetes. Recently, we have reported a novel strategy for the selective expansion of Tregs using OX40L (a TNF-superfamily ligand) and Jagged (JAG)-1 (a Notch family ligand) treatment independent of canonical TCR-signaling, but mediated through specific interaction between OX40L-OX40 and JAG1-Notch3 preferentially expressed on Tregs. OX40L-JAG1 treatment of NOD mice with soluble OX40L and JAG1 increased proliferation of peripheral Tregs and delayed the onset of diabetes. In the present study, we show that OX40L treatment significantly increased Tregs in the thymus by inducing proliferation of thymic Tregs independent of TCR-stimulation upon addition of exogenous IL-2. OX40−/− mice had reduced numbers of thymic Tregs compared to wild type (WT) controls. The reduction in thymic Treg numbers likely due to impaired ability of proliferation in response to OX40L. However, we did not observe any change in IL-2 sensitivity of thymocytes in OX40−/− mice. Mechanistic studies suggested that OX40L-IL-2 induced thymic Treg proliferation was mediated through NF-kB and AKT-mTOR-S6 signaling. Further, phenotypic characterization studies revealed a significant decrease in TIGIT+Treg population, often associated with Treg activation, in both thymus and spleen of OX40−/− mice compared to WT controls. Taken together, these results suggest a critical role for OX40L/OX40 signaling in the development as well as function of Tregs.

A novel, intergenic enhancer contributes to Il2 gene expression via chromosomal looping.

Abstract IL-2 is a key immunoregulatory cytokine with pleotropic effects on many immune cell types. Its expression is highly regulated in T cells through multiple signaling pathways, chromatin remodeling, DNA methylation, and cooperative transcription factor binding. Recently, we identified an evolutionarily conserved intergenic enhancer 83 kb upstream of the Il2 gene that augments transcription from the Il2 promoter and upstream regulatory region (URR) by >50-fold in recombinant reporter assays. Upon TCR/CD28 co-stimulation of primary CD4+ T cells, a long-range chromosomal loop is established between the −83 kb CNS and the endogenous Il2 promoter, and both regions become epigenetically marked by histone acetylation and methylation. To determine the relative contribution of the URR vs. this new distal element to inducible transcription of the Il2 gene, we deleted the URR or the −83 kb CNS in mice using CRISPR/CAS genome editing. Deletion of the URR (~500 bp beyond the TATA element) completely abolished the Il2 transcription by CD4+ T cells, while a ~500 bp deletion of the −83 kb CNS resulted in a 2- to 4-fold decrease in IL-2 production. Young mice deficient for the −83 kb enhancer exhibited no major defects in lymphoid development, however, mutant CD4+ T cells showed reduced proliferative capacity in vitro. Furthermore, TGFB-induced iTreg differentiation from mutant conventional CD4+ precursors was strongly impaired, but could be fully restored by addition of exogenous IL-2. These results show that induction of Il2 depends upon cooperation between the promoter-URR and at least one intergenic enhancer, and suggest mechanisms by which graded expression of Il2 might be achieved through ‘modular’ recruitment of distinct enhancer elements.

Interleukin-15 Enables Septic Shock by Maintaining Natural Killer Cell Integrity and Function

Abstract Interleukin-15 (IL-15) is essential for development, differentiation and function of natural killer (NK) and memory (m) CD8+T cells. Our lab previously showed that NK and CD8+T cells facilitate systemic inflammation and physiological dysfunction during septic shock. However, factors that regulate NK and CD8+T cell function during sepsis are not well characterized. We hypothesize that IL-15 promotes the pathogenesis of sepsis by maintaining NK and mCD8+T cell numbers and function. To test our hypothesis, the response of IL-15-deficient (IL-15 KO) mice to sepsis was assessed. IL-15 KO mice showed improved survival, attenuated hypothermia, and less pro-inflammatory cytokine production during septic shock caused by cecal ligation and puncture (CLP) or lipopolysaccharide (LPS). Treatment with IL-15 superagonist (IL-15 SA, IL-15/IL-15Rα complex) regenerated NK and mCD8+ T cells and re-established mortality of IL-15 KO mice during septic shock. Preventing NK cell regeneration attenuated the restoration of mortality caused by IL-15 SA. If given immediately prior to septic challenge, IL-15 neutralizing IgG M96 failed to protect against septic shock. However, M96 caused NK cell depletion and conferred protection if given 4 days prior to septic challenge. IL-15 SA treatment amplified septic shock, which was prevented by NK cell or IFNγ depletion. IL-15 SA treatment also exacerbated septic shock caused by CLP if given after the onset of sepsis. In conclusion, endogenous IL-15 doesn’t directly augment the pathogenesis of sepsis but enables septic shock by maintaining NK cell numbers and function. Exogenous IL-15 SA exacerbates severity of sepsis by activating NK cells and facilitating IFNγ production.

IL-10 enhances IgE-independent IL-33-mediated mast cell cytokine production

Abstract IgE antibodies play a critical role in antigen-mediated mast cell activation. However, mast cells can be activated via IgE-independent mechanisms including signaling via the IL-33 receptor ST2. We have previously shown that the Th2-derived cytokine IL-10 can enhance IgE-dependent mucosal mast cell activation and promote mast cell function and survival. However, whether the effects of IL-10 on mast cells are global in nature and not limited to IgE-mediated signaling is not clear. To determine whether IL-10 can prime the activation of mast cells mediated by IgE-independent signals such as IL-33, we assessed the effects of rIL-10 exposure on IL-33-stimulated mast cells and their subsequent activation via IgE. Bone marrow-derived mast cells (BMMCs) from wild-type (WT) and IL-10−/− mice were cultured with rIL-33 with or without rIL-10 and activated with DNP-IgE and antigen. Exposure to IL-10 enhanced cytokine production in both WT and IL-10−/− BMMCs, and this was significantly increased after activation via IgE. IL-10−/−BMMCs exhibited decreased cytokine production, but this was restored upon culture with rIL-10. Interestingly, IL-33 stimulation (and subsequent activation with IgE) induced comparably enhanced levels of cytokine production, specifically IL-13 and IL-6, in both WT and IL-10−/−cells, suggesting that ST2-mediated signals can overcome the lack of IL-10. However, the addition of exogenous IL-10 to IL-33-stimulated cultures further enhanced the levels of these cytokines not only in IgE-activated cells, but also in cells stimulated with IL-33 alone. Our observations therefore suggest that IL-10 can play critical roles in enhancing mast cell function both via IgE-dependent and independent mechanisms.

Beta-2 adrenergic receptor signaling prevents hyperinflammation through early release of IL-10

Abstract Innervation of the lymphoid tissues by catecholaminergic nerve endings allow the sympathetic nervous system to communicate with immune cells through the release of norepinephrine (NE). NE signals through adrenergic receptors, which are widely expressed by immune cells. We have identified a novel pathway where NE can suppress pro-inflammatory cytokine secretion from bone marrow-derived macrophages in response to multiple TLR agonists. This pathway operates through the beta2-adrenergic receptor (ADRB2), and the suppressive effect of NE depends on the early induction of the anti-inflammatory cytokine IL-10. We assessed the in vivo role of this pathway using a LPS endotoxemia model and found that ADRB2 knockout (KO) animals rapidly succumbed to a sub-lethal LPS challenge. This sensitivity is correlated with elevated serum levels of TNFα and suppressed IL-10 in ADRB2 KO animals. The lethality in the ADRB2 KO animals was rescued by administering exogenous IL-10. Additionally, the ADRB2-specific agonist salmeterol rescued wild-type animals from a lethal LPS challenge, which was reversed by neutralizing anti-IL-10 antibody. These observations suggest that ADRB2 signaling is critical for controlling inflammation through the rapid induction of IL-10. Through transcriptome analysis, the NR4A nuclear orphan family members were induced by NE, and the presence of several putative NR4A binding sites within the IL-10 promoter suggests that these factors may directly regulate IL-10 expression in response to ADRB2 signaling. Further studies will directly test the control of IL-10 expression by NR4A factors. Understanding this pathway will provide new insights into how the nervous and immune systems communicate through ADRB2 signaling.

IL-23 mediated skin inflammation is dependent on the expansion and function of RORγt expressing cells

Abstract While playing an important role in host defense against extracellular pathogens, the IL-23/IL-17 axis is inherently linked to autoimmune disease. Biologic therapies have been developed that target the p19 subunit of IL-23 and IL-17A or IL-17R; and show remarkable efficacy against a range of autoimmune conditions including Psoriasis (PsO). Despite this clinical validation, the cellular pathways induced by IL-23 remain poorly defined. In order to better understand the role of RORγt in this pathway, we administered a potent and selective inhibitor of RORγt in a model of IL-23 mediated skin inflammation, which closely models human PsO. Looking specifically at skin, to differentiate from previous studies, we show that the accumulation of RORγt expressing cells is an early event following exogenous IL-23 exposure. Expansion of these RORγt expressing cells paralleled disease progression (inflammation) with both αβ and γδ T cells contributing to this population. Inhibition of RORγt with a novel small molecule inverse agonist significantly attenuated ear inflammation and histological endpoints related to human PsO. Furthermore, use of this compound attenuated both the accumulation of RORγt positive cells and their effector function (IL-17A production). Finally, inhibition of RORγt had profound downstream consequences, leading to significant recovery of keratinocyte dysregulation and normalization of anti-microbial gene expression. Collectively our studies confirm that RORγt expressing cells are an early feature of IL-23 mediated skin inflammation, reside predominantly in the T cell compartment, and play an active role in keratinocyte biology and disease pathology.

Altered Natural Killer Cell Function in HIV-Exposed Uninfected Infants.

HIV-exposed uninfected (HEU) infants have higher rates of severe and fatal infections compared with HIV-unexposed (HUU) infants, likely due to immune perturbations. We hypothesized that alterations in natural killer (NK) cell activity might occur in HEU infants and predispose them to severe infections. Case-control study using cryopreserved peripheral blood mononuclear cells (PBMCs) at birth and 6 months from HEU infants enrolled from 2002 to 2009 and HUU infants enrolled from 2011 to 2013. NK cell phenotype and function were assessed by flow cytometry after 20-h incubation with and without K562 cells. The proportion of NK cells among PBMCs was lower at birth in 12 HEU vs. 22 HUU (1.68 vs. 10.30%, p < 0.0001) and at 6 months in 52 HEU vs. 72 HUU (3.09 vs. 4.65%, p = 0.0005). At birth, HEU NK cells demonstrated increased killing of K562 target cells (p < 0.0001) and increased expression of CD107a (21.65 vs. 12.70%, p = 0.047), but these differences resolved by 6 months. Stimulated HEU NK cells produced less interferon (IFN)γ at birth (0.77 vs. 2.64%, p = 0.008) and at 6 months (4.12 vs. 8.39%, p = 0.001), and showed reduced perforin staining at 6 months (66.95 vs. 77.30%, p = 0.0008). Analysis of cell culture supernatants indicated that lower NK cell activity in HEU was associated with reduced interleukin (IL)-12, IL-15, and IL-18. Addition of recombinant human IL-12 to stimulated HEU PBMCs restored IFNγ production to that seen in stimulated HUU cultures. NK cell proportion, phenotype, and function are altered in HEU infants. NK cell cytotoxicity and degranulation are increased in HEU at birth, but HEU NK cells have reduced IFNγ and perforin production, suggesting an adequate initial response, but decreased functional reserve. NK cell function improved with addition of exogenous IL-12, implicating impaired production of IL-12 by accessory cells. Alterations in NK cell and accessory cell function may contribute to the increased susceptibility to infection in HEU infants.

Transcription factor c-Rel is indispensable for generation of thymic but not of peripheral Foxp3+ regulatory T cells.

The transcription factor c-Rel has been shown to be crucial for development of regulatory T cells (Tregs). Recent studies have reported that the expression of transcription factor Helios in Foxp3+ Tregs correlates with thymic origin of these cells (tTregs). Notably, we found that only the Helios+Foxp3+ Treg cell population was substantially reduced in c-Rel deficient mice. In contrast to a defective tTreg development, we observed an expansion of mucosal Tregs during the induction of acute colitis in rel−/− mice. Furthermore, we found a preferential accumulation of Helios−Foxp3+ Tregs in aged c-Rel deficient mice. This unexpected finding, together with the observation that naïve CD4+ T cells convert into Tregs in vitro in the absence of c-Rel and presence of IL-2, provide an evidence that extra-thymic generation of induced and peripheral Tregs (iTregs and pTregs) is independent of c-Rel. Moreover, the treatment with IL-2/anti-IL-2 mAb (JES6-1) resulted in a widespread increase of Helios+Foxp3+ Tregs in both wild-type (WT) and rel−/− mice. These data suggest that exogenous IL-2 administration compensates for defective IL-2 production and reduced tTreg numbers in c-Rel deficient mice. Our findings reveal that c-Rel is essential for the generation of tTregs but not for that of pTregs and iTregs.

IL-21 promotes myocardial ischaemia/reperfusion injury through the modulation of neutrophil infiltration.

The immune system plays an important role in driving the acute inflammatory response following myocardial ischaemia/reperfusion injury (MIRI). IL-21 is a pleiotropic cytokine with multiple immunomodulatory effects, but its role in MIRI is not known. Myocardial injury, neutrophil infiltration and the expression of neutrophil chemokines KC (CXCL1) and MIP-2 (CXCL2) were studied in a mouse model of MIRI. Effects of IL-21 on the expression of KC and MIP-2 in neonatal mouse cardiomyocytes (CMs) and cardiac fibroblasts (CFs) were determined by real-time PCR and ELISA. The signalling mechanisms underlying these effects were explored by western blot analysis. IL-21 was elevated within the acute phase of murine MIRI. Neutralization of IL-21 attenuated myocardial injury, as illustrated by reduced infarct size, decreased cardiac troponin T levels and improved cardiac function, whereas exogenous IL-21 administration exerted opposite effects. IL-21 increased the infiltration of neutrophils and increased the expression of KC and MIP-2 in myocardial tissue following MIRI. Moreover, neutrophil depletion attenuated the IL-21-induced myocardial injury. Mechanistically, IL-21 increased the production of KC and MIP-2 in neonatal CMs and CFs, and enhanced neutrophil migration, as revealed by the migration assay. Furthermore, we demonstrated that this IL-21-mediated increase in chemokine expression involved the activation of Akt/NF-κB signalling in CMs and p38 MAPK/NF-κB signalling in CFs. Our data provide novel evidence that IL-21 plays a pathogenic role in MIRI, most likely by promoting cardiac neutrophil infiltration. Therefore, targeting IL-21 may have therapeutic potential as a treatment for MIRI. This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

In vitro immunoregulatory effects of thymoglobulin on human immune cell subpopulations

Thymoglobulin (ATG) is a polyclonal rabbit antibody against human thymocytes used as a T cell-depleting agent in organ transplantation. Its polyclonal character suggests that its effect may go far beyond just T cell depletion. The aim of this study was to further elucidate possible mechanisms underlying the suppressive activity of ATG.For in vitro studies, human peripheral blood mononuclear cells (PBMC) were incubated with ATG or control Ig for various time points. Foxp3+ regulatory cells (Tregs) and monocytes were phenotypically analyzed by flow cytometry and functionally tested by in vitro suppression assays. Cytokine levels were determined by quantitative RT- PCR, Multiplex or ELISA techniques.In vitro, the frequencies of Foxp3+ Tregs increased when human PBMC were stimulated with ATG as compared with stimulation by rabbit Ig or without stimulation. ATG-treated cells suppressed proliferation of autologous PBMC stimulated with anti-CD3 and anti-CD28 monoclonal antibodies and this suppression could be reversed by exogenous IL-2. The Foxp3+ expression dropped down on day 10, which suggests that it is transient. Monocytes and natural killer cells stimulated with ATG down-modulated CD16. Monocytes suppressed the proliferation of autologous PBMC. However, there were not statistically significant differences in IL-10, TNF-α and TGF-β1 secretion by monocytes stimulated with ATG or control rabbit Ig.These findings suggest that ATG has immunomodulatory effects that go beyond T cell depletion and induction of Foxp3+ Tregs. The induction of immunosuppressive monocytes might have a protective role in delaying transplant rejection.

Combination of IL-10 and IL-2 induces oligoclonal human CD4 T cell expansion during xenogeneic and allogeneic GVHD in humanized mice.

IL-10 is a crucial anti-inflammatory cytokine which can also exert a seemingly divergent immunostimulatory effects under certain conditions. We found high levels of the cytokine in a xenogeneic GVHD model where NOD-scid IL2rγcnull (NSG) mice were transplanted with human PBMCs in presence of IL-2. Presence of exogenous IL-10 altered the kinetics of IL-2 induced human T cell reconstitution in vivo, showing an initial delay, followed by rapid expansion. Further, compared to IL-2 alone, treatment with IL-2 in combination with IL-10 increased survival in most animals and completely protected ∼20% of mice from GVHD. Additionally, IL-2 induced expansion of both CD4+ and CD8+ xenoreactive T cells whereas a combination of IL-2 and IL-10 resulted in selective expansion of CD4+ T cells only. TCR Vβ repertoire analysis of CD4+ T cells showed that in contrast to IL-2 alone, simultaneous presence of both cytokines drastically reduced the Vβ repertoire of the expanded CD4+ T cells. Highly restricted Vβ usage was also observed when the cytokine combination was tested in an allogeneic GVHD model where NOD-scid IL2rγcnull mice expressing HLA-DR4 (NSG-DR4) were transplanted with purified CD4+ T cells from HLA-DR4 negative donors. Taken together, our results demonstrate that IL-10 can profoundly modulate the subset composition and repertoire of responding T cells during GVHD.

IL-33/ST2-mediated inflammation in macrophages is directly abrogated by IL-10 during rheumatoid arthritis.

IL-10 is an immunosuppressive cytokine produced and sensed by many immune cells and exerts a protective role in autoimmune diseases. However, the underlying mechanism by which IL-10 contributes to prevent the arthritic inflammation in macrophages is poorly understood. Herein we report on a novel anti-arthritic property of IL-10 through the inhibition of IL-33 signaling by macrophages during collagen-induced arthritis (CIA) development. We show that IL-33 expression rather than its receptor (ST2) is positively correlated with IL-10 level in active RA. IL-10 deficiency in mice leads to significant upregulation of IL-33 expression and aggravates the progression of CIA, while exogenous IL-10 treatment effectively diminishes IL-33 production in IL-10 knockout (IL-10−/−) CIA mice. We demonstrate further that the inhibitory effect of IL-10 in suppressing IL-33 production requires STAT3 activation in macrophages. Furthermore, IL-33 stimulated proinflammatory genes are notably increased in IL-10−/− CIA mice, whereas macrophages treated with recombinant IL-10 exhibit decreased IL-33 amplified inflammation and inhibited IL-33 activated NF-κB signaling pathway. Our findings indicate that IL-10 act as a negative regulator of IL-33/ST2 signaling pathways in vivo, suggesting a potential therapeutic role of IL-10 in autoimmune diseases.

Interleukin 2 and interleukin 10 function synergistically to promote CD8+ T cell cytotoxicity, which is suppressed by regulatory T cells in breast cancer

The precise role of interleukin (IL)-10 in breast cancer is not clear. Previous studies suggested a tumor-promoting role of IL-10 in breast cancer, whereas recent discoveries that IL-10 activated and expanded tumor-resident CD8+ T cells challenged the traditional view. Here, we investigated the role of IL-10 in HLA-A2-positive breast cancer patients with Grade III, Stage IIA or IIB in-situ and invasive ductal carcinoma, and compared it with that of IL-2, the canonical CD8+ T cell growth factor. We first observed that breast cancer patients presented higher serum levels of IL-2 and IL-10 than healthy controls. Upon prolonged TCR stimulation, peripheral blood CD8+ T cells from breast cancer patients tended to undergo apoptosis, which could be prevented by the addition of IL-2 and/or IL-10. The cytotoxicity of TCR-activated CD8+ T cells was also enhanced by exogenous IL-2 and/or IL-10. Interestingly, IL-2 and IL-10 demonstrated synergistic effects, since the enhancement in CD8+ T cell function when both cytokines were added was greater than the sum of the improvements mediated by each individual cytokine. IL-10 by itself could not promote the proliferation of CD8+ T cells but could significantly enhance IL-2-mediated promotion of CD8+ T cell proliferation. In addition, the cytotoxicity of tumor-infiltrating CD8+ T cells in breast tumor was elevated when both IL-2 and IL-10 were present but not when either one was absent. This synergistic effect was stopped by CD4+CD25+ regulatory T cells (Treg), which depleted IL-2 in a cell number-dependent manner. Together, these results demonstrated that IL-2 and IL-10 could work synergistically to improve the survival, proliferation, and cytotoxicity of activated CD8+ T cells, an effect suppressible by CD4+CD25+ Treg cells.