Signaling from the IL-2 receptor to the nucleus

Adjusting to self in the thymus: CD4 versus CD8 lineage commitment and regulatory T cell development

During thymic development, thymocytes adjust their TCR response based on the strength of their reactivity to self-peptide MHC complexes. This tuning process allows thymocytes with a range of self-reactivities to survive positive selection and contribute to a diverse T cell pool. In this review, we will discuss recent advances in our understanding of how thymocytes tune their responsiveness during positive selection, and we present a "sequential selection" model to explain how MHC specificity influences lineage choice. We also discuss recent evidence for cell type diversity in the medulla and discuss how this heterogeneity may contribute to medullary niches for negative selection and regulatory T cell development.

De novo design of mini-binder proteins against IL-2 receptor β chain

IL-2 regulates the immune response by interacting with different IL-2 receptor (IL-2R) subunits. High dose of IL-2 binds to IL-2Rβγc heterodimer, which induce various side effects while activating immune function. Disrupting IL-2 and IL-2R interactions can block IL-2 mediated immune response. Here, we used a computational approach to de novo design mini-binder proteins against IL-2R β chain (IL-2Rβ) to block IL-2 signaling. The hydrophobic region where IL-2 binds to IL-2Rβ was selected and the promising binding mode was broadly explored. Three mini-binders with amino acid numbers ranging from 55 to 65 were obtained and binder 1 showed the best effects in inhibiting CTLL-2 cells proliferation and STAT5 phosphorylation. Molecular dynamics simulation showed that the binding of binder 1 to IL-2Rβ was stable; the free energy of binder1/IL-2Rβ complex was lower, indicating that the affinity of binder 1 to IL-2Rβ was higher than that of IL-2. Free energy decomposition suggested that the ARG35 and ARG131 of IL-2Rβ might be the key to improve the affinity of binder. Our efforts provided new insights in developing of IL-2R blocker, offering a potential strategy for ameliorating the side effects of IL-2 treatment.

Microarray-based Analysis of Differential Gene Expression Profile in Rotenone-induced Parkinson's Disease Zebrafish Model

BACKGROUND & OBJECTIVES

Despite much clinical and laboratory research that has been performed to explore the mechanisms of Parkinson's disease (PD), its pathogenesis remains elusive to date. Therefore, this study aimed to identify possible regulators of neurodegeneration by performing microarray analysis of the zebrafish PD model's brain following rotenone exposure.

METHODS

A total of 36 adult zebrafish were divided into two groups: control (n = 17) and rotenonetreated (n = 19). Fish were treated with rotenone water (5 μg/L water) for 28 days and subjected to locomotor behavior analysis. Total RNA was extracted from the brain tissue after rotenone treatment. The cDNA synthesized was subjected to microarray analysis and subsequently validated by qPCR.

RESULTS

Administration of rotenone has significantly reduced locomotor activity in zebrafish (p < 0.05), dysregulated dopamine-related gene expression (dat, th1, and th2, p < 0.001), and reduced dopamine level in the brain (p < 0.001). In the rotenone-treated group, genes involved in cytotoxic T lymphocytes (gzm3, cd8a, p < 0.001) and T cell receptor signaling (themis, lck, p < 0.001) were upregulated significantly. Additionally, gene expression involved in microgliosis regulation (tyrobp, p < 0.001), cellular response to IL-1 (ccl34b4, il2rb, p < 0.05), and regulation of apoptotic process (dedd1, p < 0.001) were also upregulated significantly.

CONCLUSION

The mechanisms of T cell receptor signaling, microgliosis regulation, cellular response to IL-1, and apoptotic signaling pathways have potentially contributed to PD development in rotenonetreated zebrafish.

Efficacy and antitumor activity of a mutant type of interleukin 2

Interleukin-2 (IL-2) is an important cytokine in survival, expansion, function of CD8+ T cells and natural killer cells in immunotherapy of melanoma and renal cell carcinomas. Its severe toxicity following binding to its high affinity IL-2 receptor alpha (IL-2Rα) has restricted its application in cancer patients. In the present study, we investigated the antitumor efficacy and cytotoxicity of a mutated human IL-2 previously designed by selective amino acid substitutions, and its reduced affinity towards high-affinity IL-2Rα (CD25) was approved compared to the wild type IL-2 (wtIL-2). Furthermore, their ability to induce PBMC cell proliferation, and interferon-gamma secretion was compared. The mutant IL-2 also represented higher antitumor activity and more efficient cytotoxicity than wild type hIL-2. The developed mutant IL-2 can be an alternative tool in IL-2 associated immunotherapy of various cancers.

Transcriptional Differences between Canine Cutaneous Epitheliotropic Lymphoma and Immune-Mediated Dermatoses

Canine cutaneous epitheliotropic T-cell lymphoma (CETL) and immune-mediated T-cell predominant dermatoses (IMD) share several clinical and histopathological features, but differ substantially in prognosis. The discrimination of ambiguous cases may be challenging, as diagnostic tests are limited and may prove equivocal. This study aimed to investigate transcriptional differences between CETL and IMD, as a basis for further research on discriminating diagnostic biomarkers. We performed 100bp single-end sequencing on RNA extracted from formalin-fixed and paraffin-embedded skin biopsies from dogs with CETL and IMD, respectively. DESeq2 was used for principal component analysis (PCA) and differential gene expression analysis. Genes with significantly different expression were analyzed for enriched pathways using two different tools. The expression of selected genes and their proteins was validated by RT-qPCR and immunohistochemistry. PCA demonstrated the distinct gene expression profiles of CETL and IMD. In total, 503 genes were upregulated, while 4986 were downregulated in CETL compared to IMD. RT-qPCR confirmed the sequencing results for 5/6 selected genes tested, while the protein expression detected by immunohistochemistry was not entirely consistent. Our study revealed transcriptional differences between canine CETL and IMD, with similarities to human cutaneous lymphoma. Differentially expressed genes are potential discriminatory markers, but require further validation on larger sample collections.

Genomic and Transcriptomic Characterization of Natural Killer T Cell Lymphoma

Natural killer/T cell lymphoma (NKTCL) is an aggressive and heterogeneous entity of non-Hodgkin lymphoma, strongly associated with Epstein-Barr virus (EBV) infection. To identify molecular subtypes of NKTCL based on genomic structural alterations and EBV sequences, we performed multi-omics study on 128 biopsy samples of newly diagnosed NKTCL and defined three prominent subtypes, which differ significantly in cell of origin, EBV gene expression, transcriptional signatures, and responses to asparaginase-based regimens and targeted therapy. Our findings thus identify molecular networks of EBV-associated pathogenesis and suggest potential clinical strategies on NKTCL.

IL-2 Induces Transient Arrest in the G1 Phase to Protect Cervical Cancer Cells from Entering Apoptosis

Interleukin 2 (IL-2) has been used for the treatment of different types of cancer that express the IL-2 receptor (IL-2R). However, the effect of IL-2 on cervical cancer cells is unknown. IL-2R is present in normal cells of the immune system but not in the healthy cervix. We report that IL-2R is expressed in cervical cancer cells. IL-2 decreases cervical cancer cell proliferation via transient arrest of the G1 phase, which does not result in apoptosis or senescence. IL-2 upregulates the expression of p53 and p21 and downregulates cyclin D. In addition, we report the resistance of cervical cancer cells to treatments that induce apoptosis in HeLa and INBL cells. When arrested cells were treated with cisplatin, the cytokine protected cells from apoptosis induced by cisplatin. The effects of IL-2 on the cell cycle do not induce cellular senescence or activate the proapoptotic protein Bax. The cell arrest induced by IL-2 is conferring protection to cells against apoptosis.

Relationship between Multiple Sclerosis-Associated IL2RA Risk Allele Variants and Circulating T Cell Phenotypes in Healthy Genotype-Selected Controls

Single nucleotide polymorphisms (SNPs) in or near the IL2RA gene, that encodes the interleukin-2 (IL-2) receptor α (CD25), are associated with increased risk of immune-mediated diseases including multiple sclerosis (MS). We investigated how the MS-associated IL2RA SNPs rs2104286 and rs11256593 are associated with CD25 expression on T cells ex vivo by multiparameter flow cytometry in paired genotype-selected healthy controls. We observed that MS-associated IL2RA SNPs rs2104286 and rs11256593 are associated with expression of CD25 in CD4⁺ but not CD8⁺ T cells. In CD4⁺ T cells, carriers of the risk genotype had a reduced frequency of CD25⁺ T_FH1 cells (p = 0.001) and an increased frequency of CD25⁺ recent thymic emigrant cells (p = 0.006). Furthermore, carriers of the risk genotype had a reduced surface expression of CD25 in post-thymic expanded CD4⁺ T cells (CD31⁻CD45RA⁺), CD39⁺ T_Reg cells and in several non-follicular memory subsets. Our study found novel associations of MS-associated IL2RA SNPs on expression of CD25 in CD4⁺ T cell subsets. Insight into the associations of MS-associated IL2RA SNPs, as these new findings provide, offers a better understanding of CD25 variation in the immune system and can lead to new insights into how MS-associated SNPs contribute to development of MS.

Blocking IL-2 Signal In Vivo with an IL-2 Antagonist Reduces Tumor Growth through the Control of Regulatory T Cells

IL-2 is critical for peripheral tolerance mediated by regulatory T (Treg) cells, which represent an obstacle for effective cancer immunotherapy. Although IL-2 is important for effector (E) T cell function, it has been hypothesized that therapies blocking IL-2 signals weaken Treg cell activity, promoting immune responses. This hypothesis has been partially tested using anti-IL-2 or anti-IL-2R Abs with antitumor effects that cannot be exclusively attributed to lack of IL-2 signaling in vivo. In this work, we pursued an alternative strategy to block IL-2 signaling in vivo, taking advantage of the trimeric structure of the IL-2R. We designed an IL-2 mutant that conserves the capacity to bind to the αβ-chains of the IL-2R but not to the γ_c-chain, thus having a reduced signaling capacity. We show our IL-2 mutein inhibits IL-2 Treg cell-dependent differentiation and expansion. Moreover, treatment with IL-2 mutein reduces Treg cell numbers and impairs tumor growth in mice. A mathematical model was used to better understand the effect of the mutein on Treg and E T cells, suggesting suitable strategies to improve its design. Our results show that it is enough to transiently inhibit IL-2 signaling to bias E and Treg cell balance in vivo toward immunity.

Guanine and inosine nucleotides/nucleosides suppress murine T cell activation

Damaged tissues and cells release intracellular purine nucleotides, which serve as intercellular signaling factors. We previously showed that exogenously added adenine nucleotide (250 μM ATP) suppressed the activation of murine splenic T lymphocytes. Here, we examined the effects of other purine nucleotides/nucleosides on mouse T cell activation. First, we found that pretreatment of mouse spleen T cells with 250 μM GTP, GDP, GMP, guanosine, ITP, IDP, IMP or inosine significantly reduced the release of stimulus-inducible cytokine IL-2. This suppression of IL-2 release was not caused by induction of cell death. Further studies with GTP, ITP, guanosine and inosine showed that pretreatment with these nucleotides/nucleosides also suppressed release of IL-6. However, these nucleotides/nucleosides did not suppress stimulus-induced phosphorylation of ERK1/2, suggesting that the suppression of the release of inflammatory cytokines does not involve inhibition of ERK1/2 signaling. In contrast to ATP pretreatment at the same concentration, guanine or inosine nucleotides/nucleosides did not attenuate the expression of CD25. Our findings indicate that exogenous guanine or inosine nucleotides/nucleosides can suppress inflammatory cytokine release from T cells, and may be promising candidates for use as supplementary agents in the treatment of T cell-mediated immune diseases.

Adenine Nucleotides Attenuate Murine T Cell Activation Induced by Concanavalin A or T Cell Receptor Stimulation

Extracellular ATP and its metabolites affect various cellular immune responses, including T cell function, but there are apparently conflicting reports concerning the effects of adenine nucleotides on T cells. For example, it has been reported that ATP-mediated activation of P2 receptor is involved in T cell activation; activation of adenosine receptors suppresses T cell function; and 1 mM ATP induces T cell death via activation of P2X7 receptor. Therefore, in this work we investigated in detail the effects of 100–250 μM ATP, ADP, or AMP on murine T cell activation. First, an in vitro study showed that pretreatment of murine splenic T cells with 100–250 μM ATP, ADP, or AMP significantly suppressed the concanavalin A (ConA)-induced release of cytokines, including IL-2. This suppression was not due to induction of cell death via the P2X7 receptor or to an immunosuppressive effect of adenosine. ATP attenuated the expression of CD25, and decreased the cell proliferation ability of activated T cells. The release of IL-2 by ConA-stimulated lymphocytes was suppressed by post-treatment with ATP, as well as by pretreatment. These results suggest that exogenous ATP suppresses the activation of T cells. Secondly, we evaluated the effect of ATP in a ConA-treated mice. Treatment with ATP attenuated the increase of IL-2 concentration in the blood. Overall, these results suggest that adenine nucleotides might have potential as supplemental therapeutic agents for T cell-mediated immune diseases, by suppressing T cell activation.

The RNA-Binding Protein HuR Posttranscriptionally Regulates IL-2 Homeostasis and CD4+ Th2 Differentiation

Posttranscriptional gene regulation by RNA-binding proteins, such as HuR (elavl1), fine-tune gene expression in T cells, leading to powerful effects on immune responses. HuR can stabilize target mRNAs and/or promote translation by interacting with their 3' untranslated region adenylate and uridylate-rich elements. It was previously demonstrated that HuR facilitates Th2 cytokine expression by mRNA stabilization. However, its effects upon IL-2 homeostasis and CD4+ Th2 differentiation are not as well understood. We found that optimal translation of Il2ra (CD25) required interaction of its mRNA with HuR. Conditional HuR knockout in CD4+ T cells resulted in loss of IL-2 homeostasis and defects in JAK-STAT signaling, Th2 differentiation, and cytokine production. HuR-knockout CD4+ T cells from OVA-immunized mice also failed to proliferate in response to Ag. These results demonstrate that HuR plays a pivotal role in maintaining normal IL-2 homeostasis and initiating CD4+ Th2 differentiation.

The contribution of interleukin-2 to effective wound healing

Ineffective skin wound healing is a significant source of morbidity and mortality. Roughly 6.5 million Americans experience chronically open wounds and the cost of treating these wounds numbers in the billions of dollars annually. In contrast, robust wound healing can lead to the development of either hypertrophic scarring or keloidosis, both of which can cause discomfort and can be cosmetically undesirable. Appropriate wound healing requires the interplay of a variety of factors, including the skin, the local microenvironment, the immune system, and the external environment. When these interactions are perturbed, wounds can be a nidus for infection, which can cause them to remain open an extended period of time, or can scar excessively. Interleukin-2, a cytokine that directs T-cell expansion and phenotypic development, appears to play an important role in wound healing. The best-studied role for Interleukin-2 is in influencing T-cell development. However, other cell types, including fibroblasts, the skin cells responsible for closing wounds, express the Interleukin-2 receptor, and therefore may respond to Interleukin-2. Studies have shown that treatment with Interleukin-2 can improve the strength of healed skin, which implicates Interleukin-2 in the wound healing process. Furthermore, diseases that involve impaired wound healing, such as diabetes and systemic lupus erythematosus, have been linked to deficiencies in Interleukin-2 or defects Interleukin-2-receptor signaling. The focus of this review is to summarize the current understanding of the role of Interleukin-2 in wound healing, to highlight diseases in which Interleukin-2 and its receptor may contribute to impaired wound healing, and to assess Interleukin-2-modulating approaches as potential therapies to improve wound healing.

Acetylation Modulates IL-2 Receptor Signaling in T Cells

Ligand binding to the cognate cytokine receptors activates intracellular signaling by recruiting protein tyrosine kinases and other protein modification enzymes. However, the roles of protein modifications other than phosphorylation remain unclear. In this study, we examine a novel regulatory mechanism of Stat5, based on its acetylation. As for phosphorylation, IL-2 induces the acetylation of signaling molecules, including Stat5, in the murine T cell line CTLL-2. Stat5 is acetylated in the cytoplasm by CREB-binding protein (CBP). Acetylated Lys⁶⁹⁶ and Lys⁷⁰⁰ on Stat5 are critical indicators for limited proteolysis, which leads to the generation of a truncated form of Stat5. In turn, the truncated form of Stat5 prevents transcription of the full-length form of Stat5. We also demonstrate that CBP physically associates with the IL-2 receptor β-chain. CBP, found in the nucleus in resting CTLL-2 cells, relocates to the cytoplasm after IL-2 stimulation in an MEK/ERK pathway-dependent manner. Thus, IL-2-mediated acetylation plays an important role in the modulation of cytokine signaling and T cell fate.

Dynamic Long-Range Chromatin Interaction Controls Expression of IL-21 in CD4+ T Cells

IL-21, a pleiotropic cytokine strongly linked with autoimmunity and inflammation, regulates diverse immune responses. IL-21 can be potently induced in CD4(+) T cells by IL-6; however, very little is known about the mechanisms underlying the transcriptional regulation of the Il21 gene at the chromatin level. In this study, we demonstrated that a conserved noncoding sequence located 49 kb upstream of the Il21 gene contains an enhancer element that can upregulate Il21 gene expression in a STAT3- and NFAT-dependent manner. Additionally, we identified enhancer-blocking insulator elements in the Il21 locus, which constitutively bind CTCF and cohesin. In naive CD4(+) T cells, these upstream and downstream CTCF binding sites interact with each other to make a DNA loop; however, the Il21 promoter does not interact with any cis-elements in the Il21 locus. In contrast, stimulation of CD4(+) T cells with IL-6 leads to recruitment of STAT3 to the promoter and novel distal enhancer region. This induces dynamic changes in chromatin configuration, bringing the promoter and the regulatory elements in close spatial proximity. The long-range interaction between the promoter and distal enhancer region was dependent on IL-6/STAT3 signaling pathway but was disrupted in regulatory T cells, where IL-21 expression was repressed. Thus, our work uncovers a novel topological chromatin framework underlying proper transcriptional regulation of the Il21 gene.

The BMP Pathway Participates in Human Naive CD4+ T Cell Activation and Homeostasis

Bone Morphogenetic Proteins (BMPs) form a group of secreted factors that belongs to the TGF-β superfamily. Among different roles in a number of immune cell types, BMPs are known to regulate T cell development within the thymus, although the role of BMP signaling in human mature T cells remains elusive. In this study, we demonstrate that canonical BMP signaling is necessary during two critical events that regulate the size and function of human naive CD4⁺ T cell population: activation and homeostasis. Upon stimulation via TCR, naive CD4⁺ T cells upregulate the expression of BMP ligands triggering canonical BMP signaling in CD25⁺ cells. Blockade of BMP signaling severely impairs CD4⁺ T cell proliferation after activation mainly through regulation of IL-2, since the addition of this cytokine recuperates normal T cell expansion after inhibition of BMP signaling. Similarly, activation of canonical BMP pathway is required for both the maintenance of cell survival and the homeostatic proliferation induced by IL-7, a key factor for T cell homeostasis. Moreover, upregulation of two critical receptors for T cell homeostasis, CXCR4 and CCR9, triggered by IL-7 is also abrogated in the absence of BMP signaling. Collectively, we describe important roles of the canonical BMP signaling in human naive CD4⁺ T cell activation and homeostasis that could be valuable for clinical application.

Proprotein convertase FURIN regulates T cell receptor-induced transactivation

Antigen emergence rapidly stimulates T cells, which leads to changes in cytokine production, cell proliferation, and differentiation. Some of the key molecules involved in these events, such as TGF-β1 and NOTCH1, are synthesized initially as inactive precursors and are proteolytically activated during T cell activation. PCSKs regulate proprotein maturation by catalyzing the proteolytic cleavage of their substrates. The prototype PCSK FURIN is induced upon TCR activation, and its expression in T cells is critical for the maintenance of peripheral immune tolerance. In this study, we tested the hypothesis that FURIN regulates T cell activation. Our data demonstrate that IL-2 is increased initially in FURIN-deficient mouse CD4(+) T cells, but the TCR-induced IL-2 mRNA expression is not sustained in the absence of FURIN. Accordingly, the inhibition of FURIN in human Jurkat T cell lines also results in a decrease in IL-2 production, whereas the overexpression of WT FURIN is associated with elevated IL-2 levels. In Jurkat cells, FURIN is dispensable for immediate TCR signaling steps, such as ERK, ZAP70, or LAT phosphorylation. However, with the use of gene reporter assays, we demonstrate that FURIN regulates the AP-1, NFAT, and NF-κB transcription factors. Finally, by performing a transcription factor-binding site enrichment analysis on FURIN-dependent transcriptomes, we identify the FURIN-regulated transcription factors in mouse CD4(+) T cell subsets. Collectively, our work confirms the hypothesis that the TCR-regulated protease FURIN plays an important role in T cell activation and that it can specifically modulate TCR-activated transactivation.

Dendritic cell derived IL-2 inhibits survival of terminally mature cells via an autocrine signaling pathway

DCs are crucial for sensing pathogens and triggering immune response. Upon activation by pathogen-associated molecular pattern (PAMP) ligands, GM-CSF myeloid DCs (GM-DCs) secrete several cytokines, including IL-2. DC IL-2 has been shown to be important for innate and adaptive immune responses; however, IL-2 importance in DC physiology has never been demonstrated. Here, we show that autocrine IL-2 signaling is functional in murine GM-DCs in an early time window after PAMPs stimulation. IL-2 signaling selectively activates the JAK/STAT5 pathway by assembling holo-receptor complexes at the cell surface. Using the sensitivity of targeted mass spectrometry, we show conclusively that GM-DCs express CD122, the IL-2 receptor β-chain, at steady state. In myeloid DCs, this cytokine pathway inhibits survival of PAMP-matured GM-DCs which is crucial for maintaining immune tolerance and preventing autoimmunity. Our findings suggest that immune regulation by this novel autocrine signaling pathway can potentially be used in DC immunotherapy.

Calcium mobilization is both required and sufficient for initiating chromatin decondensation during activation of peripheral T-cells

Antigen engagement of the T-cell receptor (TCR) induces a rapid and dramatic decondensation of chromatin that is necessary for T-cell activation. This decondensation makes T-cells competent to respond to interleukin-2 providing a mechanism to ensure clonotypic proliferation during an immune response. Using murine T-cells, we investigated the mechanism by which TCR signaling can initiate chromatin decondensation, focusing on the role of calcium mobilization. During T-cell activation, calcium is first released from intracellular stores, followed by influx of extracellular calcium via store operated calcium entry. We show that mobilization of intracellular calcium is required for TCR-induced chromatin decondensation. However, the decondensation is not dependent on the activity of the downstream transcription factor NFAT. Furthermore, we show that the influx of extracellular calcium is dispensable for initiating chromatin decondensation. Finally, we show that mobilization of calcium from intracellular stores is sufficient to induce decondensation, independent of TCR engagement. Collectively, our data suggest that chromatin decondensation in peripheral T-cells is controlled by modulating intracellular calcium levels.

Immunosuppressive peptides and their therapeutic applications

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T cell signaling has a pivotal role in autoimmunity and immunosuppression.

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Immunosuppressive pharmaceuticals often exhibit severe side-effects in patients.

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Gene-encoded peptides have potential as immunosuppressive drug candidates.

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Cyclotides are stable peptides that offer enhanced oral administration properties.

The immune system is vital for detecting and evading endogenous and exogenous threats to the body. Failure to regulate this homeostasis leads to autoimmunity, which is often associated with malfunctioning T cell signaling. Several medications are available to suppress over-reactive T lymphocytes, but many of the currently marketed drugs produce severe and life-threatening side-effects. Ribosomally synthesized peptides are gaining recognition from the pharmaceutical industry for their enhanced selectivity and decreased toxicity compared with small molecules; in particular, circular peptides exhibit remarkable stability and increased oral administration properties. For example, plant cyclotides effectively inhibit T lymphocyte proliferation. They are composed of a head-to-tail cyclized backbone and a cystine-knot motif, which confers them with remarkable stability, thus making them attractive pharmaceutical tools.

CD40 activation rescues antiviral CD8⁺ T cells from PD-1-mediated exhaustion

The intrahepatic immune environment is normally biased towards tolerance. Nonetheless, effective antiviral immune responses can be induced against hepatotropic pathogens. To examine the immunological basis of this paradox we studied the ability of hepatocellularly expressed hepatitis B virus (HBV) to activate immunologically naïve HBV-specific CD8⁺ T cell receptor (TCR) transgenic T cells after adoptive transfer to HBV transgenic mice. Intrahepatic priming triggered vigorous in situ T cell proliferation but failed to induce interferon gamma production or cytolytic effector function. In contrast, the same T cells differentiated into cytolytic effector T cells in HBV transgenic mice if Programmed Death 1 (PD-1) expression was genetically ablated, suggesting that intrahepatic antigen presentation per se triggers negative regulatory signals that prevent the functional differentiation of naïve CD8⁺ T cells. Surprisingly, coadministration of an agonistic anti-CD40 antibody (αCD40) inhibited PD-1 induction and restored T cell effector function, thereby inhibiting viral gene expression and causing a necroinflammatory liver disease. Importantly, the depletion of myeloid dendritic cells (mDCs) strongly diminished the αCD40 mediated functional differentiation of HBV-specific CD8⁺ T cells, suggesting that activation of mDCs was responsible for the functional differentiation of HBV-specific CD8⁺ T cells in αCD40 treated animals. These results demonstrate that antigen-specific, PD-1-mediated CD8⁺ T cell exhaustion can be rescued by CD40-mediated mDC-activation.

Hepatitis B virus (HBV) infection is responsible for more than 500,000 deaths annually as a result of the immune-mediated chronic liver damage it induces. The HBV specific CD8⁺ T cell response contributes to the pathogenesis of liver disease and viral clearance, and the failure to induce and/or sustain a vigorous CD8⁺ T cell response results in viral persistence and causes chronic necroinflammatory liver disease. To understand how the HBV-specific CD8⁺ T cell response is generated in response to intrahepatically expressed HBV, we generated T cell receptor transgenic mice whose CD8⁺ T cells are specific for HBV core or HBV envelope antigens. We find that these T cells are primed in the liver when they are adoptively transferred into HBV transgenic mouse recipients whose livers produce infectious virus particles, and that they proliferate vigorously in situ but do not differentiate into functional effector T cells after antigen recognition. Functional differentiation is suppressed by dominant negative regulatory signals, including PD-1, unless they are suppressed by anti-CD40 activation of myeloid dendritic cells.

Shikonin Suppresses Human T Lymphocyte Activation through Inhibition of IKK β Activity and JNK Phosphorylation

The key role of T cells has been elaborated in mediating immune responses and pathogenesis of human inflammatory and autoimmune conditions. In the current study the effect of shikonin, a compound isolated from a medicinal plant, on inhibition of T-cell activation was firstly examined by using primary human T lymphocytes isolated from buffy coat. Results showed that shikonin dose dependently suppressed T-cell proliferation, IL-2 and IFN-γ secretion, CD69 and CD25 expression, as well as cell cycle arrest activated by costimulation of PMA/ionomycin or OKT-3/CD28 monoclonal antibodies. Moreover, these inhibitory responses mediated by shikonin were found to be associated with suppression of the NF-κB signaling pathway via inhibition of the IKKα/β phosphorylation, IκB-α phosphorylation and degradation, and NF-κB nuclear translocation by directly decreasing IKKβ activity. Moreover, shikonin suppressed JNK phosphorylation in the MAPKs pathway of T cells. In this connection, we conclude that shikonin could suppress T lymphocyte activation through suppressing IKKβ activity and JNK signaling, which suggests that shikonin is valuable for further investigation as a potential immunosuppressive agent.

Stability of the recombinant anti‑erbB2 scFv‑Fc‑interleukin‑2 fusion protein and its inhibition of HER2‑overexpressing tumor cells

The anti‑erbB2 scFv‑Fc‑IL‑2 fusion protein (HFI) is the basis for development of a novel targeted anticancer drug, in particular for the treatment of HER2‑positive cancer patients. HFI was fused with the anti‑erbB2 antibody and human IL‑2 by genetic engineering technology and by antibody targeting characteristics of HFI. IL‑2 was recruited to target cells to block HER2 signaling, inhibit or kill tumor cells, improve the immune capacity, reduce the dose of antibody and IL‑2 synergy. In order to analyse HFI drug ability, HFI plasmid stability was verified by HFI expression of the trend of volume changes. Additionally, HFI could easily precipitate and had progressive characteristics and thus, the buffer system of the additive phosphate‑citric acid buffer, arginine, Triton X‑100 or Tween‑80, the establishment of a microfiltration, ion exchange, affinity chromatography and gel filtration chromatography‑based purification process were explored. HFI samples were obtained according to the requirements of purity, activity and homogeneity. In vivo, HFI significantly delayed HER2 overexpression of non‑small cell lung cancer (Calu‑3) in human non‑small cell lung cancer xenografts in nude mice, and the inhibition rate was more than 60% (P<0.05) in the group treated with 1 mg/kg the HFI dose; HFI significantly inhibited HER2 expression of breast cancer (FVB/neu) transgenic mouse tumor growth in 1 mg/kg of the HFI dose group, and in the following treatment the 400 mm3 tumors disappeared completely. Combined with other HFI test data analysis, HFI not only has good prospects, but also laid the foundation for the development of antibody‑cytokine fusion protein‑like drugs.

GB virus C envelope protein E2 inhibits TCR-induced IL-2 production and alters IL-2-signaling pathways

GB virus type C (GBV-C) viremia is associated with reduced CD4+ T cell expansion following IL-2 therapy and with a reduction in T cell activation in HIV-infected individuals. The mechanism(s) by which GBV-C might alter T cell activation or IL-2 signaling have not been studied. In this study, we assess IL-2 release, IL-2R expression, IL-2 signaling, and cell proliferation in tet-off Jurkat cells expressing the GBV-C envelope glycoprotein (E2) following activation through the TCR. TCR activation was induced by incubation in anti-CD3/CD28 Abs. IL-2 release was measured by ELISA, STAT5 phosphorylation was assessed by immunoblot, and IL-2Rα (CD25) expression and cell proliferation were determined by flow cytometry. IL-2 and IL-2Rα steady-state mRNA levels were measured by real-time PCR. GBV-C E2 expression significantly inhibited IL-2 release, CD25 expression, STAT5 phosphorylation, and cellular proliferation in Jurkat cells following activation through the TCR compared with control cell lines. Reducing E2 expression by doxycycline reversed the inhibitory effects observed in the E2-expressing cells. The N-terminal 219 aa of E2 was sufficient to inhibit IL-2 signaling. Addition of purified recombinant GBV-C E2 protein to primary human CD4+ and CD8+ T cells inhibited TCR activation-induced IL-2 release and upregulation of IL-2Rα expression. These data provide evidence that the GBV-C E2 protein may contribute to the block in CD4+ T cell expansion following IL-2 therapy in HIV-infected individuals. Furthermore, the effects of GBV-C on IL-2 and IL-2-signaling pathways may contribute to the reduction in chronic immune activation observed in GBV-C/HIV-coinfected individuals.

The potential beneficial effects of drugs on the immune response to vaccination

Many immunotherapeutic agents in phase II cancer studies have given optimistic results, which were not confirmed in larger randomized studies. Here we explore the evidence that, contrary to previous opinion, many chemotherapeutic agents and other classes of drugs may enhance the response to therapeutic vaccines by reducing inflammation and/or by inhibiting regulatory T lymphocytes or myeloid-derived suppressor cells. In addition, some of these agents, such as the immunomodulatory drugs, may produce marked costimulatory activities as in the case of lenalidomide, which also has marked anti-inflammatory properties. With the first approval for a vaccine-based therapy for prostate cancer, we propose that many more vaccines will be able to achieve approval, especially when combined with the optimal chemotherapy and/or immunomodulatory drug schedule.

Molecular mechanism of interleukin-2-induced mucosal homeostasis

Sustained damage to the mucosal lining in patients with inflammatory bowel disease (IBD) facilitates translocation of intestinal microbes to submucosal immune cells leading to chronic inflammation. Previously, we demonstrated the role of Jak3 in IL-2-induced intestinal epithelial cell (IEC) migration, one of the early events during intestinal wound repair. In this study, we demonstrate that IL-2 also plays a role in IEC homeostasis through concentration-dependent regulation of IEC proliferation and cell death. At lower concentrations (≤50 U/ml), IL-2 promoted proliferation, while at higher concentrations (100 U/ml), it promoted apoptosis. Activation by IL-2 led to tyrosine phosphorylation-dependent interactions between Jak3 and p52ShcA only at lower concentrations. Phosphatase SHP1 dephosphorylated IL-2-induced phosphorylated p52ShcA. Higher concentrations of IL-2 decreased the phosphorylation of Jak3 and p52ShcA, disrupted their interactions, redistributed Jak3 to the nucleus, and induced apoptosis in IEC. IL-2 also induced dose-dependent upregulation of p52shcA and downregulation of jak3-mRNA. Constitutive overexpression and mir-shRNA-mediated knockdown studies showed that expression of both Jak3 and p52ShcA were necessary for IL-2-induced proliferation of IEC. Doxycycline-regulated sh-RNA expression demonstrated that IL-2-induced downregulation of jak3-mRNA was responsible for higher IL-2-induced apoptosis in IEC. Collectively, these data demonstrate a novel mechanism of IL-2-induced mucosal homeostasis through posttranslational and transcriptional regulation of Jak3 and p52ShcA.

FERM domain mutations induce gain of function in JAK3 in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is an incurable disease where most patients succumb within the first year of diagnosis. Both standard chemotherapy regimens and mAbs directed against ATLL tumor markers do not alter this aggressive clinical course. Therapeutic development would be facilitated by the discovery of genes and pathways that drive or initiate ATLL, but so far amenable drug targets have not been forthcoming. Because the IL-2 signaling pathway plays a prominent role in ATLL pathogenesis, mutational analysis of pathway components should yield interesting results. In this study, we focused on JAK3, the nonreceptor tyrosine kinase that signals from the IL-2R, where activating mutations have been found in diverse neoplasms. We screened 36 ATLL patients and 24 ethnically matched controls and found 4 patients with mutations in JAK3. These somatic, missense mutations occurred in the N-terminal FERM (founding members: band 4.1, ezrin, radixin, and moesin) domain and induced gain of function in JAK3. Importantly, we show that these mutant JAK3s are inhibited with a specific kinase inhibitor already in human clinical testing. Our findings underscore the importance of this pathway in ATLL development and offer a therapeutic handle for this incurable cancer.

Type I diabetes-associated tolerogenic properties of interleukin-2

Type 1 Diabetes (T1D) results from insulin-producing beta cells destruction by diabetogenic T lymphocytes in humans and nonobese diabetic (NOD) mice. The breakdown of tolerance has been associated with a defect in the number and the function of naturally occurring regulatory T cells (nTreg) that are the master player in peripheral tolerance. Gene knockout experiments in mouse models have shown a nonredundant activity of IL-2 related to its critical role in inducing nTreg and controlling peripheral T cell tolerance. Whereas strong evidence has suggested that IL-2 is critically required for nTreg-mediated T1D control, several fundamental questions remain to be addressed. In this paper, we highlight the recent findings and controversies regarding the tolerogenic properties of IL-2 mediated through nTreg. We further discuss a potential link between the immunomodulatory role of interleukin-2 and the pathogenesis of type 1 diabetes.

Chromatin condensation via the condensin II complex is required for peripheral T-cell quiescence

Naive T cells encountering their cognate antigen become activated and acquire the ability to proliferate in response to cytokines. Stat5 is an essential component in this response. We demonstrate that Stat5 cannot access DNA in naive T cells and acquires this ability only after T-cell receptor (TCR) engagement. The transition is not associated with changes in DNA methylation or global histone modification but rather chromatin decondensation. Condensation occurs during thymocyte development and proper condensation is dependent on kleisin-β of the condensin II complex. Our findings suggest that this unique chromatin condensation, which can affect interpretations of chromatin accessibility assays, is required for proper T-cell development and maintenance of the quiescent state. This mechanism ensures that cytokine driven proliferation can only occur in the context of TCR stimulation.

FoxO1 - the key for the pathogenesis and therapy of acne?

Five main factors play a pivotal role in the pathogenesis of acne: androgen dependence, follicular retention hyperkeratosis, increased sebaceous lipogenesis, increased colonization with P. acnes, and inflammatory events. This paper offers a solution for the pathogenesis of acne and explains all major pathogenic factors at the genomic level by a relative deficiency of the nuclear transcription factor FoxO1. Nuclear FoxO1 suppresses androgen receptor, other important nuclear receptors and key genes of cell proliferation, lipid biosynthesis and inflammatory cytokines. Elevated growth factors during puberty and persistent growth factor signals due to Western life style stimulate the export of FoxO1 out of the nucleus into the cytoplasm via activation of the phos-phoinositide-3-kinase (PI3K)/Akt pathway. By this mechanism, genes and nuclear receptors involved in acne are derepressed leading to increased androgen receptor-mediated signal transduction, increased cell proliferation of androgen-dependent cells, induction of sebaceous lipogenesis and upregulation of Toll-like-receptor-2-dependent inflammatory cytokines. All known acne-inducing factors exert their action by reduction of nuclear FoxO1 levels. In contrast, retinoids, antibiotics and dietary intervention will increase the nuclear content of FoxO1, thereby normalizing increased transcription of genes involved in acne. Various receptor-mediated growth factor signals are integrated at the level of PI3K/Akt activation which finally results in nuclear FoxO1 deficiency.

CISH and susceptibility to infectious diseases

BACKGROUND

The interleukin-2-mediated immune response is critical for host defense against infectious pathogens. Cytokine-inducible SRC homology 2 (SH2) domain protein (CISH), a suppressor of cytokine signaling, controls interleukin-2 signaling.

METHODS

Using a case-control design, we tested for an association between CISH polymorphisms and susceptibility to major infectious diseases (bacteremia, tuberculosis, and severe malaria) in blood samples from 8402 persons in Gambia, Hong Kong, Kenya, Malawi, and Vietnam. We had previously tested 20 other immune-related genes in one or more of these sample collections.

RESULTS

We observed associations between variant alleles of multiple CISH polymorphisms and increased susceptibility to each infectious disease in each of the study populations. When all five single-nucleotide polymorphisms (SNPs) (at positions -639, -292, -163, +1320, and +3415 [all relative to CISH]) within the CISH-associated locus were considered together in a multiple-SNP score, we found an association between CISH genetic variants and susceptibility to bacteremia, malaria, and tuberculosis (P=3.8x10(-11) for all comparisons), with -292 accounting for most of the association signal (P=4.58x10(-7)). Peripheral-blood mononuclear cells obtained from adult subjects carrying the -292 variant, as compared with wild-type cells, showed a muted response to the stimulation of interleukin-2 production--that is, 25 to 40% less CISH expression.

CONCLUSIONS

Variants of CISH are associated with susceptibility to diseases caused by diverse infectious pathogens, suggesting that negative regulators of cytokine signaling have a role in immunity against various infectious diseases. The overall risk of one of these infectious diseases was increased by at least 18% among persons carrying the variant CISH alleles.

NetPath: a public resource of curated signal transduction pathways

NetPath, a novel community resource of curated human signaling pathways is presented and its utility demonstrated using immune signaling data.

We have developed NetPath as a resource of curated human signaling pathways. As an initial step, NetPath provides detailed maps of a number of immune signaling pathways, which include approximately 1,600 reactions annotated from the literature and more than 2,800 instances of transcriptionally regulated genes - all linked to over 5,500 published articles. We anticipate NetPath to become a consolidated resource for human signaling pathways that should enable systems biology approaches.

How diverse--CD4 effector T cells and their functions

CD4 effector T cells, also called helper T (Th) cells, are the functional cells for executing immune functions. Balanced immune responses can only be achieved by proper regulation of the differentiation and function of Th cells. Dysregulated Th cell function often leads to inefficient clearance of pathogens and causes inflammatory diseases and autoimmunity. Since the establishment of the Th1-Th2 dogma in the 1980s, different lineages of effector T cells have been identified that not only promote but also suppress immune responses. Through years of collective efforts, much information was gained on the function and regulation of different subsets of Th cells. In this review, we attempt to sample the essence of what has been learnt in this field over the past two decades. We will discuss the classification and immunological functions of effector T cells, the determinants for effector T cell differentiation, as well as the relationship between different lineages of effector T cells.

CCR5 expression levels influence NFAT translocation, IL-2 production, and subsequent signaling events during T lymphocyte activation

Ligands of CCR5, the major coreceptor of HIV-1, costimulate T lymphocyte activation. However, the full impact of CCR5 expression on T cell responses remains unknown. Here, we show that compared with CCR5(+/+), T cells from CCR5(-/-) mice secrete lower amounts of IL-2, and a similar phenotype is observed in humans who lack CCR5 expression (CCR5-Delta32/Delta32 homozygotes) as well as after Ab-mediated blockade of CCR5 in human T cells genetically intact for CCR5 expression. Conversely, overexpression of CCR5 in human T cells results in enhanced IL-2 production. CCR5 surface levels correlate positively with IL-2 protein and mRNA abundance, suggesting that CCR5 affects IL-2 gene regulation. Signaling via CCR5 resulted in NFAT transactivation in T cells that was blocked by Abs against CCR5 agonists, suggesting a link between CCR5 and downstream pathways that influence IL-2 expression. Furthermore, murine T cells lacking CCR5 had reduced levels of intranuclear NFAT following activation. Accordingly, CCR5 expression also promoted IL-2-dependent events, including CD25 expression, STAT5 phosphorylation, and T cell proliferation. We therefore suggest that by influencing a NFAT-mediated pathway that regulates IL-2 production and IL-2-dependent events, CCR5 may play a critical role in T cell responses. In accord with our prior inferences from genetic-epidemiologic studies, such CCR5-dependent responses might constitute a viral entry-independent mechanism by which CCR5 may influence HIV-AIDS pathogenesis.

Tubulin Polymerization Modulates Interleukin-2 Receptor Signal Transduction in Human T Cells

Few data exist on the modulation of cytokine receptor signaling by the actin or tubulin cytoskeleton. Therefore, we studied interleukin-2 receptor (IL-2R) signaling in phytohemagglutinine (PHA)-pretreated human T cells in the context of alterations in the cytoskeletal system induced by cytochalasin D (CyD), jasplaklinolide (Jas), taxol (Tax), or colchicine (Col). We found that changes in cytoskeletal tubulin polymerization altered the strength of several IL-2-triggered signals. Moreover, Tax-induced tubulin hyperpolymerization augmented the surface expression of the IL-2R ss -chain and enhanced the association of the IL-2R beta -chain with cytoskeletal tubulin. The IL-2R beta-chain, in turn, was constitutively associated with tubulin and, more weakly, actin. To exclude the possibility that these associations are artifacts caused by PHA, we confirmed them in T cells from TCR-transgenic DO 11.10 mice stimulated with their nominal antigen. We conclude that altered polymerization of cytoskeletal components, especially tubulin, is accompanied by modulation of IL-2 signaling at the receptor level.

The IL-15 receptor {alpha} chain cytoplasmic domain is critical for normal IL-15Ralpha function but is not required for trans-presentation

IL-15 is critical for natural killer (NK)-cell development and function and for memory CD8(+) T-cell homeostasis. The IL-15 receptor consists of IL-15Ralpha, IL-2Rbeta, and the common cytokine receptor gamma chain (gamma(c)). IL-15Ralpha is known to "trans-present" IL-15 to an IL-2Rbeta/gamma(c) heterodimeric receptor on responding cells to initiate signaling. To investigate the importance of the IL-15Ralpha cytoplasmic domain, we generated a chimeric receptor consisting of the extracellular domain of IL-15Ralpha and intracellular domain of IL-2Ralpha (IL-15Ralpha(ext)/IL-2Ralpha(int)) and examined its function in 32D cells, in knock-in (KI) mice, and in adoptive-transfer experiments. The chimeric protein exhibited decreased cell-surface expression, and KI mice exhibited diminished NK, NKT, and CD8(+) T-cell development and defects in T-cell functional responses. However, 32D cells expressing the chimeric receptor had less IL-15-induced proliferation than wild-type (WT) transfectants with similar levels of IL-15Ralpha expression, indicating a signaling role for the IL-15Ralpha cytoplasmic domain beyond its effect on expression, and demonstrating that the IL-2Ralpha and IL-15Ralpha cytoplasmic domains are functionally distinct. Interestingly, adoptive-transfer experiments indicated that the chimeric IL-15Ralpha(ext)/IL-2Ralpha(int) receptor still supports trans-presentation. These experiments collectively indicate that IL-15Ralpha can act in cis in addition to acting in trans to present IL-15 to responding cells.

The IL-2/CD25 pathway determines susceptibility to T1D in humans and NOD mice

Although the interleukin-2 (IL-2)/IL-2R signaling pathway has been the focus of numerous studies, certain aspects of its molecular regulation are not well characterized, especially in non-T cells, and a more complete understanding of the pathway is necessary to discern the functional basis of the genetic association between the IL-2-IL-21 and IL-2RA/CD25 gene regions and T1D in humans. Genetic variation in these regions may promote T1D susceptibility by influencing transcription and/or splicing and, hence, IL-2 and IL-2RA/CD25 expression at the protein level in different immune cell subsets; thus, there is a need to establish links between the genetic variation and immune cell phenotypes and functions in humans, which can be further investigated and validated in mouse models. The detection and characterization of genetically determined immunophenotypes should aid in elucidating disease mechanisms and may enable future monitoring of disease initiation and progression in prediabetic subjects and of responses to therapeutic intervention.

The regulatory, inflammatory, and T cell programming roles of interleukin-2 (IL-2)

Signaling through IL-2 induces the activation of pathways that lead to the proliferation, survival and cytokine production of effector T cells. However, through negative feedback mechanisms, internalization of the IL-2 receptor, induction of activation-induced cell death, and the generation of regulatory T cells, IL-2 also promotes the suppression of inflammatory responses. In regulatory T cells, IL-2 signaling upregulates the expression of FoxP3. Regulatory T cell induction by TGF-beta also requires IL-2. Additionally, pro-inflammatory and pro-survival pathways involving PI3K upon IL-2 stimulation is inhibited by PTEN in regulatory T cells. Importantly, IL-2 signaling is key for the development, expansion and maintenance of regulatory T cells. However, gamma(c) cytokines can replace requirements for IL-2 in regulatory T cells, although not with the same efficacy. The dual roles of IL-2 in inflammation are demonstrated in that mice deficient in both FoxP3 and IL-2 display less severe symptoms compared to FoxP3 deficient mice. Finally, IL-2 not only plays a key role in the induction of effector T cells and regulatory T cells, it also inhibits IL-17 producing T cells. By understanding complex dynamics of IL-2 interactions in the inflammatory response, therapies may be developed or modified for regulating immune related diseases.

T-cell development and function are modulated by dual specificity phosphatase DUSP5

Interleukin-2 (IL-2) is a pleiotropic cytokine that regulates lymphocyte proliferation and peripheral tolerance. IL-2 activates mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase, and signal transducer and activator of transcription (STAT) pathways and modulates expression of target genes. Systematic analysis of IL-2 target genes has revealed regulation of potential feedback inhibitors of IL-2 signaling, including several suppressor of cytokine signaling (SOCS) family members as well as MAPK pathway-regulating dual specificity phosphatases (DUSPs). Here we have evaluated the in vivo actions of DUSP5, an extracellular signal-regulated kinase 1/2 (ERK1/2)-specific phosphatase, by generating transgenic mice overexpressing DUSP5 within the lymphoid compartment. We show that transgenic DUSP5 expression results in a block in thymocyte development at the double positive stage. We also demonstrate that DUSP5-expressing mature T cells exhibit decreased IL-2-dependent proliferation and defective IL-2-mediated induction of genes. Finally, DUSP5 transgenic mice develop autoimmune symptoms, suggesting a role for the MAPK pathway in the regulation of tolerance. Thus, proper regulation of DUSP5 activity is critical for normal immune system development, IL-2 actions, and tolerance.