Interleukin-2 Signaling Research Articles

Neuronal Release of Cytokine IL-3 Triggered by Mechanosensitive Autostimulation of the P2X7 Receptor Is Neuroprotective.

Mechanical strain due to increased pressure or swelling activates inflammatory responses in many neural systems. As cytokines and chemokine messengers lead to both pro-inflammatory and neuroprotective actions, understanding the signaling patterns triggered by mechanical stress may help improve overall outcomes. While cytokine signaling in neural systems is often associated with glial cells like astrocytes and microglia, the contribution of neurons themselves to the cytokine response is underappreciated and has bearing on any balanced response. Mechanical stretch of isolated neurons was previously shown to trigger ATP release through pannexin hemichannels and autostimulation of P2X7 receptors (P2X7Rs) on the neural membrane. Given that P2X7Rs are linked to cytokine activation in other cells, this study investigates the link between neuronal stretch and cytokine release through a P2X7-dependent pathway. Cytokine assays showed application of a 4% strain to isolated rat retinal ganglion cells (RGCs) released multiple cytokines. The P2X7R agonist BzATP also released multiple cytokines; Interleukin 3 (IL-3), TNF-α, CXCL9, VEGF, L-selectin, IL-4, GM-CSF, IL-10, IL-1Rα, MIP and CCL20 were released by both stimuli, with the release of IL-3 greatest with either stimuli. Stretch-dependent IL-3 release was confirmed with ELISA and blocked by P2X7R antagonists A438079 and Brilliant Blue G (BBG), implicating autostimulation of the P2X7R in stretch-dependent IL-3 release. Neuronal IL-3 release triggered by BzATP required extracellular calcium. The IL-3Rα receptor was expressed on RGCs but not astrocytes, and both IL-3Rα and IL-3 itself were predominantly expressed in the retinal ganglion cell layer of adult retinal sections, implying autostimulation of receptors by released IL-3. While the number of surviving ganglion cells decreased with time in culture, the addition of IL-3 protected against this loss of neurons. Expression of mRNA for IL-3 and IL-3Rα increased in rat retinas stretched with moderate intraocular pressure (IOP) elevation; BBG blocked the rise in IL-3, implicating a role for the P2X7R in transcriptional regulation in vivo. In summary, mechanical stretch triggers release of cytokines from neurons that can convey neuroprotection. The enhancement of these signals in vivo implicates P2X7R-mediated IL-3 signaling as an endogenous pathway that could minimize damage following neuronal exposure to chronic mechanical strain.

Blockade of interleukin-27 signaling reduces GVHD in mice by augmenting Treg reconstitution and stabilizing Foxp3 expression

AbstractReestablishment of competent regulatory pathways has emerged as a strategy to reduce the severity of graft-versus-host disease (GVHD), and recalibrate the effector and regulatory arms of the immune system. However, clinically feasible, cost-effective strategies that do not require extensive ex vivo cellular manipulation have remained elusive. In the current study, we demonstrate that inhibition of the interleukin-27p28 (IL-27p28) signaling pathway through antibody blockade or genetic ablation prevented lethal GVHD in multiple murine transplant models. Moreover, protection from GVHD was attributable to augmented global reconstitution of CD4+ natural regulatory T cells (nTregs), CD4+ induced Tregs (iTregs), and CD8+ iTregs, and was more potent than temporally concordant blockade of IL-6 signaling. Inhibition of IL-27p28 also enhanced the suppressive capacity of adoptively transferred CD4+ nTregs by increasing the stability of Foxp3 expression. Notably, blockade of IL-27p28 signaling reduced T-cell–derived-IL-10 production in conventional T cells; however, there was no corresponding effect in CD4+ or CD8+ Tregs, indicating that IL-27 inhibition had differential effects on IL-10 production and preserved a mechanistic pathway by which Tregs are known to suppress GVHD. Targeting of IL-27 therefore represents a novel strategy for the in vivo expansion of Tregs and subsequent prevention of GVHD without the requirement for ex vivo cellular manipulation, and provides additional support for the critical proinflammatory role that members of the IL-6 and IL-12 cytokine families play in GVHD biology.

Therapeutic efficacy of monthly subcutaneous injection of daclizumab in relapsing multiple sclerosis.

Despite the availability of multiple disease-modifying therapies for relapsing multiple sclerosis (MS), there remains a need for highly efficacious targeted therapy with a favorable benefit–risk profile and attributes that encourage a high level of treatment adherence. Daclizumab is a humanized monoclonal antibody directed against CD25, the α subunit of the high-affinity interleukin 2 (IL-2) receptor, that reversibly modulates IL-2 signaling. Daclizumab treatment leads to antagonism of proinflammatory, activated T lymphocyte function and expansion of immunoregulatory CD56bright natural killer cells, and has the potential to, at least in part, rectify the imbalance between immune tolerance and autoimmunity in relapsing MS. The clinical pharmacology, efficacy, and safety of subcutaneous daclizumab have been evaluated extensively in a large clinical study program. In pivotal studies, daclizumab demonstrated superior efficacy in reducing clinical and radiologic measures of MS disease activity compared with placebo or intramuscular interferon beta-1a, a standard-of-care therapy for relapsing MS. The risk of hepatic disorders, cutaneous events, and infections was modestly increased. The monthly subcutaneous self-injection dosing regimen of daclizumab may be advantageous in maintaining patient adherence to treatment, which is important for optimal outcomes with MS disease-modifying therapy. Daclizumab has been approved in the US and in the European Union and represents an effective new treatment option for patients with relapsing forms of MS, and is currently under review by other regulatory agencies.

Interleukin-21 signaling in B cells, but not in T cells, is indispensable for the development of collagen-induced arthritis in mice.

BackgroundInterleukin-21 (IL-21) is a T-cell-derived cytokine whose receptor is expressed on a variety of cells and therefore might have pleiotropic roles in the pathogenesis of rheumatoid arthritis (RA). In this study, we investigated the involvement of IL-21 signaling in the development of collagen-induced arthritis (CIA), an animal model of RA, using IL-21 receptor knockout (Il21r KO) mice.MethodsIl21r KO mice or wild-type (WT) C57BL/6 mice were immunized with chicken type II collagen (CII) emulsified in complete Freund adjuvant on day 0 and were given a boost injection on day 21. The production of anti-CII antibody, development of T-cell and B-cell subsets, and T-cell responses to CII were analyzed. CIA was induced in Rag2 KO mice to which combinations of WT or Il21r KO CD4 T cells and WT or Il21r KO B cells had been transferred, in order to examine the role of IL-21 signaling in each cell subset.ResultsIl21r KO mice were resistant to the development of CIA. CII-specific IgG but not IgM production was impaired in Il21r KO mice. This is consistent with a reduction of germinal center B cells in the draining lymph nodes. In contrast, CII-specific Th1 and Th17 responses were unaffected in Il21r KO mice. There was also no difference in the number of CII-specific follicular helper T cells between WT and Il21r KO mice. By analyzing the development of CIA in T-cell and B-cell mixed transfer experiments, we confirmed that IL-21 receptor expression on B cells, but not on T cells, was essential for the development of CIA.ConclusionIL-21 signaling in B cells, but not in T cells, plays essential roles in the production of pathogenic autoantibodies that induce CIA development.

Design, synthesis, and evaluation of 4,6-diaminonicotinamide derivatives as novel and potent immunomodulators targeting JAK3

In organ transplantation, T cell-mediated immune responses play a key role in the rejection of allografts. Janus kinase 3 (JAK3) is specifically expressed in hematopoietic cells and associated with regulation of T cell development via interleukin-2 signaling pathway. Here, we designed novel 4,6-diaminonicotinamide derivatives as immunomodulators targeting JAK3 for prevention of transplant rejection. Our optimization of C4- and C6-substituents and docking calculations to JAK3 protein confirmed that the 4,6-diaminonicotinamide scaffold resulted in potent inhibition of JAK3. We also investigated avoidance of human ether-a-go-go related gene (hERG) inhibitory activity. Selected compound 28 in combination with tacrolimus prevented allograft rejection in a rat heterotopic cardiac transplantation model.

Synergistic immunologic targets for the treatment of prostate cancer.

Prostate cancer is a common disease and, while detection and treatment have advanced, it remains a significant cause of morbidity and mortality in men. Research suggests significant involvement of the immune system in the pathogenesis and progression of prostate cancer, indicating that immunologic therapies may benefit patients. Two immunologic factors, interleukin-2 and transforming growth factor-β, may be especially attractive therapeutic targets for prostate cancer. Specifically, an increase in interleukin-2 signaling and a decrease in transforming growth factor-β signaling might help improve immunologic recognition and targeting of tumor cells. The purpose of this review is to highlight the evidence that interleukin-2 and blockade of transforming growth factor-β could be used to target prostate cancer based on current understanding of immune function in the context of prostate cancer. Additionally, current treatments related to these two factors for prostate and other cancers will be used to strengthen the argument for this strategy.

Optimal interleukin-7 receptor-mediated signaling, cell cycle progression and viability of T-cell acute lymphoblastic leukemia cells rely on casein kinase 2 activity

Interleukin-7 and interleukin-7 receptor are essential for normal T-cell development and homeostasis, whereas excessive interleukin-7/interleukin-7 receptor-mediated signaling promotes leukemogenesis. The protein kinase, casein kinase 2, is overexpressed and hyperactivated in cancer, including T-cell acute lymphoblastic leukemia. Herein, we show that while interleukin-7 had a minor but significant positive effect on casein kinase 2 activity in leukemia T-cells, casein kinase 2 activity was mandatory for optimal interleukin-7/interleukin-7 receptor-mediated signaling. Casein kinase 2 pharmacological inhibition impaired signal transducer and activator of transcription 5 and phosphoinositide 3-kinase/v-Akt murine thymoma viral oncogene homolog 1 pathway activation triggered by interleukin-7 or by mutational activation of interleukin-7 receptor. By contrast, forced expression of casein kinase 2 augmented interleukin-7 signaling in human embryonic kidney 293T cells reconstituted with the interleukin-7 receptor machinery. Casein kinase 2 inactivation prevented interleukin-7-induced B-cell lymphoma 2 upregulation, maintenance of mitochondrial homeostasis and viability of T-cell acute lymphoblastic leukemia cell lines and primary leukemia cells collected from patients at diagnosis. Casein kinase 2 inhibition further abrogated interleukin-7-mediated cell growth and upregulation of the transferrin receptor, and blocked cyclin A and E upregulation and cell cycle progression. Notably, casein kinase 2 was also required for the viability of mutant interleukin-7 receptor expressing leukemia T-cells. Overall, our study identifies casein kinase 2 as a major player in the effects of interleukin-7 and interleukin-7 receptor in T-cell acute lymphoblastic leukemia. This further highlights the potential relevance of targeting casein kinase 2 in this malignancy.

Role of IL-33 and ST2 signalling pathway in multiple sclerosis: expression by oligodendrocytes and inhibition of myelination in central nervous system.

Recent research findings have provided convincing evidence indicating a role for Interleukin-33 (IL-33) signalling pathway in a number of central nervous system (CNS) diseases including multiple sclerosis (MS) and Alzheimer’s disease. However, the exact function of IL-33 molecule within the CNS under normal and pathological conditions is currently unknown. In this study, we have mapped cellular expression of IL-33 and its receptor ST2 by immunohistochemistry in the brain tissues of MS patients and appropriate controls; and investigated the functional significance of these findings in vitro using a myelinating culture system. Our results demonstrate that IL-33 is expressed by neurons, astrocytes and microglia as well as oligodendrocytes, while ST2 is expressed in the lesions by oligodendrocytes and within and around axons. Furthermore, the expression levels and patterns of IL-33 and ST2 in the lesions of acute and chronic MS patient brain samples are enhanced compared with the healthy brain tissues. Finally, our data using rat myelinating co-cultures suggest that IL-33 may play an important role in MS development by inhibiting CNS myelination.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-016-0344-1) contains supplementary material, which is available to authorized users.

Kynurenine Reduces Memory CD4 T-Cell Survival by Interfering with Interleukin-2 Signaling Early during HIV-1 Infection.

Early HIV-1 infection is characterized by enhanced tryptophan catabolism, which contributes to immune suppression and disease progression. However, the mechanism by which kynurenine, a tryptophan-related metabolite, induces immune suppression remains poorly understood. Herein, we show that the increased production of kynurenine correlates with defective interleukin-2 (IL-2) signaling in memory CD4 T cells from HIV-infected subjects. Defective IL-2 signaling in these subjects, which drives reduced protection from Fas-mediated apoptosis, was also associated with memory CD4 T-cell loss. Treatment of memory CD4 T cells with the concentration of kynurenine found in plasma inhibited IL-2 signaling through the production of reactive oxygen species. We further show that IL-2 signaling in memory CD4 T cells is improved by the antioxidant N-acetylcysteine. Early initiation of antiretroviral therapy restored the IL-2 response in memory CD4 T cells by reducing reactive oxygen species and kynurenine production. The study findings provide a kynurenine-dependent mechanism through IL-2 signaling for reduced CD4 T-cell survival, which can be reversed by early treatment initiation in HIV-1 infection. The persistence of functional memory CD4 T cells represents the basis for long-lasting immune protection in individuals after exposure to HIV-1. Unfortunately, primary HIV-1 infection results in the massive loss of these cells within weeks of infection, which is mainly driven by inflammation and massive infection by the virus. These new findings show that the enhanced production of kynurenine, a metabolite related to tryptophan catabolism, also impairs memory CD4 T-cell survival and interferes with IL-2 signaling early during HIV-1 infection.

IL-33 signaling is essential to attenuate viral-induced encephalitis development by downregulating iNOS expression in the central nervous system.

BackgroundViral encephalitis is a common cause of lethal infections in humans, and several different viruses are documented to be responsible. Rocio virus is a flavivirus that causes a severe lethal encephalitis syndrome in humans and also mice, providing an interesting model to study the CNS compartmentalized immune response. Interleukin 33 (IL-33), a member of the IL-1 family, is an immunomodulatory cytokine that is highly expressed in the CNS. However, the role of IL-33 on viral encephalitis remains unclear. Therefore, we aimed to explore how the IL-33/ST2 axis regulates the local immune response during Rocio virus infection.MethodsWild-type (WT), ST2 (ST2−/−), and nitric oxide synthase-deficient mice (iNOS−/−) and Stat6 (Stat6−/−)-deficient mice were infected with different concentrations of the Rocio virus by intraperitoneal route, the cytokine mRNA level in CNS was analyzed by qPCR, and cellular immunophenotyping was performed on infected mice by the flow cytometry of isolated CNS mononuclear cells.ResultsWe have shown that the mRNA expression of IL-33 and ST2 receptors is increased in the CNS of Rocio virus-infected WT mice and that ST2−/− mice showed increased susceptibility to infection. ST2 deficiency was correlated with increased tissue pathology, cellular infiltration, and tumor necrosis factor alpha (TNF-α) and interferon-gamma (IFN-γ) mRNA levels and higher viral load in the CNS, compared with wild-type mice. The increased Th1 cytokine levels released in the CNS acted on infiltrating macrophages, as evidenced by flow cytometry characterization of cellular infiltrates, inducing the expression of iNOS, contributing to brain injury. Moreover, iNOS−/− mice were more resistant to Rocio virus encephalitis, presenting a lower clinical score and reduced mortality rate, despite the increased tissue pathology.ConclusionsWe provide evidences of a specific role for IL-33 receptor signaling in nitric oxide induction through local IFN-γ modulation, suggesting that nitric oxide overproduction might have an important role in the progression of experimental viral encephalitis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0628-1) contains supplementary material, which is available to authorized users.

High IL-7 levels in the bone marrow microenvironment mediate imatinib resistance and predict disease progression in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a three-stage myeloproliferative disease caused by translocation between chromosomes 9 and 22. Although tyrosine kinase inhibitors (TKI) are highly effective in the treatment of CML, numerous clinical trials have shown that many patients become refractory or drug resistance, especially those in the blastic crisis of CML. The molecular mechanisms underlying CML, however, remain poorly understood. In the present study, we used a coculture model to address possible mechanisms underlying the involvement of bone marrow microenvironment in the drug resistance of CML. Our data show that interleukin-7(IL-7) levels in the bone marrow of CML patients in blastic crisis are significantly higher than those of both healthy persons and CML patients in chronic and accelerated phases. The increased IL-7 was secreted by mesenchymal stem cells (MSC) in the bone marrow, which may protect leukemic cells from apoptosis induced by imatinib through JAK1/STAT5 signaling pathway. Our findings suggest that therapeutic strategies IL-7 signaling pathway may represent a promising approach for improving CML therapy, especially for patients in blastic crisis.

Interleukin-15 receptor α on hepatic stellate cells regulates hepatic fibrogenesis in mice

Interleukin-15 (IL-15) and its high affinity receptor interleukin-15 receptor alpha (IL-15Rα) are widely expressed in immune cells and hepatic resident cells. IL-15 signaling has important functions in homeostasis of natural killer (NK), natural killer T (NKT) and cytotoxic T (CD8(+) T) cells, and in liver regeneration. We hypothesized that IL-15 has a protective role in liver fibrosis progression by maintaining NK cell homeostasis. Fibrosis was induced using two mechanistically distinct models. Congenic bone marrow transplantation was used to evaluate the contribution of IL-15 signaling from various compartments to NK, CD8(+) T and NKT cell homeostasis and fibrogenesis. The gene expression profile of hepatic stellate cell (HSC) from IL-15Rα knockout (IL-15RαKO) mice and wild-type mice were captured using microarray analysis and validated in isolated HSC. Quantitative real-time PCR was used to assess repressors of collagen transcription. IL-15RαKO mice exhibited more fibrosis in both models. IL-15 signaling from specific types of hepatic cells had divergent roles in maintaining liver NK, CD8(+) T and NKT cells, with a direct and protective role on radio-resistant non-parenchymal cells beyond the control of NK homeostasis. HSCs isolated from IL-15RαKO mice demonstrated upregulation of collagen production. Finally, IL-15RαKO HSC with or without transforming growth factor beta (TGF-β) stimulation exhibited increased expression of fibrosis markers and decreased collagen transcription repressors expression. IL-15Rα signaling has a direct anti-fibrotic effect independent of preserving NK homeostasis. These findings establish a rationale to further explore the anti-fibrotic potential of enhancing IL-15 signaling in HSCs. We investigated how a cellular protein, Interleukin-15 (IL-15), decreases the amount of scar tissue that is formed upon liver injury. We found that IL-15 and its receptor decrease the amount of scar tissue that is created by specialized liver cells (called stellate cells) and increase the number of a specific subgroup of immune cells (natural killer cells) that are known to eliminate stellate cells. GSE45612, GSE 68001 and GSE 25097.

Natural TFH arise in the thymus and periphery of young naive mice

Abstract T follicular helper cells (TFH) localize to B cell follicles and secrete Interleukin 21 (IL21), a cytokine that is vital for driving the proliferation of antigen-stimulated B cells within germinal centers and their subsequent differentiation into memory B cells and antibody-secreting plasma cells. Much of the current understanding of TFH is limited to studies following immunization of adult mice. Therefore, the ontological processes by which TFH naturally develop and express IL21 are poorly understood. Here we take advantage of a novel IL21-venus fluorescent protein reporter mouse to show that a major fraction of the earliest activated CD4 T cells that develop spontaneously in the thymi and the peripheries of young naive mice express IL21 within 2 weeks of birth. This population is rivaled in frequency only by FoxP3 natural T regulatory cells (nTREG) cells. Results from RNAseq profiling, their partial developmental dependence on IL6 and IL21 signaling and durability after adoptive transfers are all consistent with the generation of a novel, natural TFH (nTFH) population. This nTFH population is functionally defined by IL21 and is able to persist in that differentiation state in naive mice. We further show that thymic development of nTFH requires AIRE, while FoxP3 nTREG act in the periphery to restrain nTFH. We conclude that the precocious and robust presentation of nTFH in naive mice is caused by inherent self-reactivity that is developmentally driven by encounter with promiscuous self-antigens through AIRE. TREG are therefore the primary means by which nTFH are prevented from exercising their pathogenic potential in the periphery.

HIV-1 Infection-Induced Suppression of the Let-7i/IL-2 Axis Contributes to CD4(+) T Cell Death.

The mechanisms underlying HIV-1-mediated CD4+ T cell depletion are highly complicated. Interleukin-2 (IL-2) is a key cytokine that maintains the survival and proliferation of activated CD4+ T cells. IL-2 levels are disturbed during HIV-1 infection, but the underlying mechanism(s) requires further investigation. We have reported that cellular microRNA (miRNA) let-7i upregulates IL-2 expression by targeting the promoter TATA-box region, which functions as a positive regulator. In this study, we found that HIV-1 infection decreases the expression of let-7i in CD4+ T cells by attenuating its promoter activity. The reduced let-7i miRNA expression led to a decline in IL-2 levels. A let-7i mimic increased IL-2 expression and subsequently enhanced the resistance of CD4+ T cells to HIV-1-induced apoptosis. By contrast, the blockage of let-7i with a specific inhibitor resulted in elevated CD4+ T cell apoptosis during HIV-1 infection. Furthermore, by knocking down the expression of IL-2, we found that the let-7i-mediated CD4+ T cell resistance to apoptosis during HIV-1 infection was dependent on IL-2 signaling rather than an alternative CD95-mediated cell-death pathway. Taken together, our findings reveal a novel pathway for HIV-1-induced dysregulation of IL-2 cytokines and depletion of CD4+ T-lymphocytes.

PSGL-1 Is an Immune Checkpoint Regulator that Promotes T Cell Exhaustion

Chronic viruses and cancers thwart immune responses in humans by inducing Tcell dysfunction. Using a murine chronic virus that models human infections, we investigated the function of the adhesion molecule, P-selectin glycoprotein ligand-1 (PSGL-1), that is upregulated on responding Tcells. PSGL-1-deficient mice cleared the virus due to increased intrinsic survival of multifunctional effector Tcells that had downregulated PD-1 as well as other inhibitory receptors. Notably, this response resulted in CD4(+)-T-cell-dependent immunopathology. Mechanistically, PSGL-1 ligation on exhausted CD8(+) Tcells inhibited Tcell receptor (TCR) and interleukin-2 (IL-2) signaling and upregulated PD-1, leading to diminished survival with TCR stimulation. In models of melanoma cancer in which Tcell dysfunction occurs, PSGL-1 deficiency led to PD-1 downregulation, improved Tcell responses, and tumor control. Thus, PSGL-1 plays a fundamental role in balancing viral control and immunopathology and also functions to regulate Tcell responses in the tumor microenvironment.

Differential regulation of TH1, TFH, and TCM gene programs by cytokine-mediated events

Abstract During the course of an immune response, multiple effector T helper cell types emerge to combat the initial infection, with subsequent emergence of long-term CD4+ T memory cells to ensure that a second exposure to the same pathogen will not cause disease. CD4+ T helper cell populations that are critical for this process include T helper 1 (TH1) and T follicular Helper (TFH) effector cells and long-lasting central memory T (TCM) cells. Previous work has demonstrated a level of flexibility between effector TH1 and TFH-like cell populations, with the respective gene programs regulated by alterations in interleukin 2 (IL-2) signaling. Here, we demonstrate that in response to decreased IL-2 signaling, effector TH1 cells are capable of initiating the expression of both TFH and TCM-like gene programs, including cell surface expression of IL-6Ra and IL-7R. Importantly, exposure of these cells to either IL-6 or IL-7 augments or inhibits the TFH gene program, respectively, suggesting a potential mechanism whereby cytokine availability may influence TFH or TCM cell function. Consistent with this model, we have identified a novel population of IL-6Ra+IL-7R+ cells that emerge at late time points post-infection in an in vivo mouse model of influenza infection. Further research into the temporal and spatial expression of IL-2, IL-6, and IL-7 in the modulation of these cells represents an exciting avenue of research with wide-ranging therapeutic implications.

Negative regulation of IL-2 signaling by β2 adrenergic receptor

Abstract T, B, and natural killer (NK) cells are required for normal immune response and regulated by cytokines such as interleukin 2 (IL-2). Cell signals are propagated following receptor-ligand engagement to control recruitment and activation of effector proteins. The IL-2 receptor β subunit (IL-2Rβ) serves in this capacity and is known to be phosphorylated on tyrosine, serine, and threonine residues. Regulation of lymphocytes is also influenced by the nervous system through the β2 adrenergic receptor (β2AR), and both pathways ultimately affect cell trafficking, proliferation, differentiation, and cytokine production. Signaling through either IL-2Rβ or the β2AR has been extensively studied, however, their potential cross-talk has yet to be fully characterized. Here we hypothesize that engagement of β2AR regulates IL-2 receptor signaling. Cells were treated with β2AR agonists and then stimulated with or without IL-2. Agonists reduced IL-2 induced proliferation in a dose dependent manner. To identify the mechanism, receptor phosphorylation and activation of downstream targets was assessed using phosphospecific antibodies. Pretreatment of cells with β2AR agonists diminished IL-2-induced phosphorylation of IL-2Rβ as well as the activation of downstream signaling molecules. In contrast, in the absence of IL-2, a biphasic β2AR agonist-induced phosphorylation of specific serine and threonine residues on IL-2Rβ associated to its activation was observed, while tyrosine phosphorylation changes were not detected. Downstream signaling molecules were differentially activated. In conclusion, the cross-talk between IL-2Rβ and β2AR could represent a novel regulatory mechanism of IL-2 signaling important for immunoregulation.

Advances of the interleukin-21 signaling pathway in immunity and angiogenesis.

Interleukin-21 (IL-21) and its receptor (IL-21R) are broadly expressed on human B cells, activated T cells and other myeloid cells. IL-21 cooperates with IL-6 and transforming growth factor-β to regulate T-cell differentiation. IL-21-mediated human B cell and dendritic cells differentiation requires signal transducer and activator of transcription 3 (STAT3), and also induces B-cell apoptosis dependents on the Toll-like receptor signal. Recently, in vitro and in vivo experiments showed that IL-21/IL-21R regulate angiogenesis through STAT3. IL-21 signaling pathways are complex due to its cooperation with other transcriptional factors, such as interferon regulatory factor 4 and granulocyte-macrophage colony-stimulating factor. The Janus kinase-STAT pathway has been the most extensively studied. With the increase in the understanding of IL-21 biology in the context of each specific disease or pathological condition, IL-21 could be a new therapeutic target for immune-related disease.

Annexin A6 regulates interleukin-2-mediated T-cell proliferation.

Annexin A6 (AnxA6) has been implicated in cell signalling by contributing to the organisation of the plasma membrane. Here we examined whether AnxA6 regulates signalling and proliferation in T cells. We used a contact hypersensitivity model to immune challenge wild-type (WT) and AnxA6(-/-) mice and found that the in vivo proliferation of CD4(+) T cells, but not CD8(+) T cells, was impaired in AnxA6(-/-) relative to WT mice. However, T-cell migration and signalling through the T-cell receptor ex vivo was similar between T cells isolated from AnxA6(-/-) and WT mice. In contrast, interleukin-2 (IL-2) signalling was reduced in AnxA6(-/-) compared with WT T cells. Further, AnxA6-deficient T cells had reduced membrane order and cholesterol levels. Taken together, our data suggest that AnxA6 regulates IL-2 homeostasis and sensitivity in T cells by sustaining a lipid raft-like membrane environment.

Requirement of interleukin 7 signaling for anti-tumor immune response under lymphopenic conditions in a murine lung carcinoma model.

Induction of lymphopenia before adoptive transfer of T cells was followed by lymphopenia-induced proliferation (LIP) and generated a potent anti-tumor immune response in rodents and in a clinical setting. Previously, we reported that CD28 signaling is essential for the differentiation of functional effector cytotoxic T lymphocytes (CTLs) under lymphopenic conditions and sequential LIP of T cells. In this study, to clarify the correlation between LIP and the anti-tumor effect, LIP was inhibited with interleukin 7 (IL7) receptor blockade at various stages, and the anti-tumor effect then assessed. We confirmed that IL7 signaling at the start of LIP is crucial for the anti-tumor immune response. In contrast, continuous IL7 signaling was not required for tumor regression, although LIP of naïve CD8+ T cells is usually regulated by IL7. The expansion and migration of CTLs in lymphopenic hosts depend on IL7 signaling during the induction phase. Here, we propose that IL7 signaling and subsequent LIP of T cells have distinct roles in the induction of T cell immunity during lymphopenia.