Suppressor of cytokine signaling 3 regulates CD8 T-cell proliferation by inhibition of interleukins 6 and 27

Immunopathology in human pulmonary tuberculosis: Inflammatory changes in the plasma milieu and impaired host immune cell functions

Host immune response is key for protection in tuberculosis, but the causative agent, Mycobacterium (M.) tuberculosis, manages to survive despite immune surveillance. Key mechanisms of immune protection have been identified, but the role of immunopathology in the peripheral blood of tuberculosis patients remains unclear. Tuberculosis immunopathology in the blood is characterised by patterns of immunosuppression and hyperinflammation. These seemingly contradictory findings and the pronounced heterogeneity made it difficult to interpret the results from previous studies and to derive implications of immunopathology. However, novel approaches based on comprehensive data analyses and revitalisation of an ancient plasma milieu in vitro assay connected inflammation with immunosuppressive factors in tuberculosis. Moreover, interrelations between the aberrant plasma milieu and immune cell pathology were observed. This review provides an overview of studies on changes in plasma milieu and discusses recent findings linking plasma factors to T-cell and monocyte/macrophage pathology in pulmonary tuberculosis patients.

Role of SOCS and VHL Proteins in Neuronal Differentiation and Development

The basic helix-loop-helix factors play a central role in neuronal differentiation and nervous system development, which involve the Notch and signal transducer and activator of transcription (STAT)/small mother against decapentaplegic signaling pathways. Neural stem cells differentiate into three nervous system lineages, and the suppressor of cytokine signaling (SOCS) and von Hippel-Lindau (VHL) proteins are involved in this neuronal differentiation. The SOCS and VHL proteins both contain homologous structures comprising the BC-box motif. SOCSs recruit Elongin C, Elongin B, Cullin5(Cul5), and Rbx2, whereas VHL recruits Elongin C, Elongin B, Cul2, and Rbx1. SOCSs form SBC-Cul5/E3 complexes, and VHL forms a VBC-Cul2/E3 complex. These complexes degrade the target protein and suppress its downstream transduction pathway by acting as E3 ligases via the ubiquitin-proteasome system. The Janus kinase (JAK) is the main target protein of the E3 ligase SBC-Cul5, whereas hypoxia-inducible factor is the primary target protein of the E3 ligase VBC-Cul2; nonetheless, VBC-Cul2 also targets the JAK. SOCSs not only act on the ubiquitin-proteasome system but also act directly on JAKs to suppress the Janus kinase-signal transduction and activator of transcription (JAK-STAT) pathway. Both SOCS and VHL are expressed in the nervous system, predominantly in brain neurons in the embryonic stage. Both SOCS and VHL induce neuronal differentiation. SOCS is involved in differentiation into neurons, whereas VHL is involved in differentiation into neurons and oligodendrocytes; both proteins promote neurite outgrowth. It has also been suggested that the inactivation of these proteins may lead to the development of nervous system malignancies and that these proteins may function as tumor suppressors. The mechanism of action of SOCS and VHL involved in neuronal differentiation and nervous system development is thought to be mediated through the inhibition of downstream signaling pathways, JAK-STAT, and hypoxia-inducible factor-vascular endothelial growth factor pathways. In addition, because SOCS and VHL promote nerve regeneration, they are expected to be applied in neuronal regenerative medicine for traumatic brain injury and stroke.

Socs3b regulates the development and function of innate immune cells in zebrafish

Introduction

Suppressor of cytokine signaling 3 (SOCS3) is a critical component of the negative feedback regulation that controls signaling by cytokines and other factors thereby ensuring that important processes such as hematopoiesis and inflammation occur at appropriate levels.

Methods

To gain further insights into SOCS3 function, the zebrafish socs3b gene was investigated through analysis of a knockout line generated using CRISPR/Cas9-mediated genome editing.

Results

Zebrafish socs3b knockout embryos displayed elevated numbers of neutrophils during primitive and definitive hematopoiesis but macrophage numbers were not altered. However, the absence of socs3b reduced neutrophil functionality but enhanced macrophage responses. Adult socs3b knockout zebrafish displayed reduced survival that correlated with an eye pathology involving extensive infiltration of neutrophils and macrophages along with immune cell dysregulation in other tissues.

Discussion

These findings identify a conserved role for Socs3b in the regulation of neutrophil production and macrophage activation.

Ewing Sarcoma and Osteosarcoma Have Distinct Immune Signatures and Intercellular Communication Networks

PURPOSE

Ewing sarcoma and osteosarcoma are primary bone sarcomas occurring most commonly in adolescents. Metastatic and relapsed disease are associated with dismal prognosis. Although effective for some soft tissue sarcomas, current immunotherapeutic approaches for the treatment of bone sarcomas have been largely ineffective, necessitating a deeper understanding of bone sarcoma immunobiology.

EXPERIMENTAL DESIGN

Multiplex immunofluorescence analysis of immune infiltration in relapsed versus primary disease was conducted. To better understand immune states and drivers of immune infiltration, especially during disease progression, we performed single-cell RNA sequencing (scRNAseq) of immune populations from paired blood and bone sarcoma tumor samples.

RESULTS

Our multiplex immunofluorescence analysis revealed increased immune infiltration in relapsed versus primary disease in both Ewing sarcoma and osteosarcoma. scRNAseq analyses revealed terminally exhausted CD8+ T cells expressing co-inhibitory receptors in osteosarcoma and an effector T-cell subpopulation in Ewing sarcoma. In addition, distinct subsets of CD14+CD16+ macrophages were present in Ewing sarcoma and osteosarcoma. To determine pathways driving tumor immune infiltration, we conducted intercellular communication analyses and uncovered shared mechanisms of immune infiltration driven by CD14+CD16+ macrophages and unique pathways of immune infiltration driven by CXCL10 and CXCL12 in osteosarcoma.

CONCLUSIONS

Our study provides preclinical rationale for future investigation of specific immunotherapeutic targets upon relapse and provides an invaluable resource of immunologic data from bone sarcomas.

Self-Renewing Islet TCF1+ CD8 T Cells Undergo IL-27-Controlled Differentiation to Become TCF1- Terminal Effectors during the Progression of Type 1 Diabetes

In type 1 diabetes (T1D) autoreactive CD8 T cells infiltrate pancreatic islets and destroy insulin-producing β cells. Progression to T1D onset is a chronic process, which suggests that the effector activity of β-cell autoreactive CD8 T cells needs to be maintained throughout the course of disease development. The mechanism that sustains diabetogenic CD8 T cell effectors during the course of T1D progression has not been completely defined. Here we used single-cell RNA sequencing to gain further insight into the phenotypic complexity of islet-infiltrating CD8 T cells in NOD mice. We identified two functionally distinct subsets of activated CD8 T cells, CD44^highTCF1⁺CXCR6^- and CD44^highTCF1^-CXCR6⁺, in islets of prediabetic NOD mice. Compared with CD44^highTCF1⁺CXCR6^- CD8 T cells, the CD44^highTCF1^-CXCR6⁺ subset expressed higher levels of inhibitory and cytotoxic molecules and was more prone to apoptosis. Adoptive cell transfer experiments revealed that CD44^highTCF1⁺CXCR6^- CD8 T cells, through continuous generation of the CD44^highTCF1^-CXCR6⁺ subset, were more capable than the latter population to promote insulitis and the development of T1D. We further showed that direct IL-27 signaling in CD8 T cells promoted the generation of terminal effectors from the CD44^highTCF1⁺CXCR6^- population. These results indicate that islet CD44^highTCF1⁺CXCR6^- CD8 T cells are a progenitor-like subset with self-renewing capacity, and, under an IL-27-controlled mechanism, they differentiate into the CD44^highTCF1^-CXCR6⁺ terminal effector population. Our study provides new insight into the sustainability of the CD8 T cell response in the pathogenesis of T1D.

Competitive binding of STATs to receptor phospho-Tyr motifs accounts for altered cytokine responses

Cytokines elicit pleiotropic and non-redundant activities despite strong overlap in their usage of receptors, JAKs and STATs molecules. We use IL-6 and IL-27 to ask how two cytokines activating the same signaling pathway have different biological roles. We found that IL-27 induces more sustained STAT1 phosphorylation than IL-6, with the two cytokines inducing comparable levels of STAT3 phosphorylation. Mathematical and statistical modeling of IL-6 and IL-27 signaling identified STAT3 binding to GP130, and STAT1 binding to IL-27Rα, as the main dynamical processes contributing to sustained pSTAT1 levels by IL-27. Mutation of Tyr613 on IL-27Rα decreased IL-27-induced STAT1 phosphorylation by 80% but had limited effect on STAT3 phosphorgylation. Strong receptor/STAT coupling by IL-27 initiated a unique gene expression program, which required sustained STAT1 phosphorylation and IRF1 expression and was enriched in classical Interferon Stimulated Genes. Interestingly, the STAT/receptor coupling exhibited by IL-6/IL-27 was altered in patients with systemic lupus erythematosus (SLE). IL-6/IL-27 induced a more potent STAT1 activation in SLE patients than in healthy controls, which correlated with higher STAT1 expression in these patients. Partial inhibition of JAK activation by sub-saturating doses of Tofacitinib specifically lowered the levels of STAT1 activation by IL-6. Our data show that receptor and STATs concentrations critically contribute to shape cytokine responses and generate functional pleiotropy in health and disease.

Suppressive effects of vitamin C-treated induced-regulatory T cells on heart allograft rejection under vitamin C-deficient or -sufficient conditions

Foxp3 stability of vitamin C-treated induced-regulatory T cells (V-iTregs) is superior to that of conventional iTregs (C-iTregs). However, the role of V-iTregs in allograft rejection under vitamin C-deficient conditions, such as those seen in humans, remains unclear. We aimed to elucidate the role of vitamin C treatment on generation and maintenance of iTregs from gulo knockout (Gulo-KO) mice as well as wild type (WT) mice, and in vitro and in vivo suppressive effects of V-iTregs on heart allograft rejection in either Gulo-KO or WT recipient mice. Conversion efficiency of iTregs was similar between C- and V-iTregs in both WT and Gulo-KO mice. V-iTregs from WT or Gulo-KO mice showed better in vitro Foxp3 stability than C-iTregs, although there was no difference between WT V-iTregs and Gulo-KO V-iTregs. Furthermore, V-iTregs from WT or Gulo-KO mice suppressed in vitro T cell proliferation better than C-iTregs. Heterotrophic heart transplantation from BALB/c mice to WT or vitamin C-deficient Gulo-KO C57BL/6J mice was performed following adoptive transfer of C- or V-iTregs. V-iTregs as well as C-iTregs prolonged heart allograft survival in WT and Gulo-KO mice. However, there was no difference between the C- and V-iTreg groups. Supplementation of low- or high-dose vitamin C did not induce significant changes in heart allograft survival in Gulo-KO recipients that had received V-iTregs. In conclusion, V-iTregs do not exert better suppressive effects on heart allograft survival than C-iTregs in either WT or vitamin C-deficient recipients.

Granulocyte Colony-Stimulating Factor Attenuates Renal Ischemia-Reperfusion Injury by Inducing Myeloid-Derived Suppressor Cells

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF) can increase populations of myeloid-derived suppressor cells, innate immune suppressors that play an immunoregulatory role in antitumor immunity. However, the roles of myeloid-derived suppressor cells and G-CSF in renal ischemia-reperfusion injury remain unclear.

METHODS

We used mouse models of ischemia-reperfusion injury to investigate whether G-CSF can attenuate renal injury by increasing infiltration of myeloid-derived suppressor cells into kidney tissue.

RESULTS

G-CSF treatment before ischemia-reperfusion injury subsequently attenuated acute renal dysfunction, tissue injury, and tubular apoptosis. Additionally, G-CSF treatment suppressed renal infiltration of macrophages and T cells as well as renal levels of IL-6, MCP-1, IL-12, TNF-α, and IFN-γ, but it increased levels of IL-10, arginase-1, and reactive oxygen species. Moreover, administering G-CSF after ischemia-reperfusion injury improved the recovery of renal function and attenuated renal fibrosis on day 28. G-CSF treatment increased renal infiltration of myeloid-derived suppressor cells (F4/80^-CD11b⁺Gr-1^int), especially the granulocytic myeloid-derived suppressor cell population (CD11b⁺Ly6Gi^ntLy6C^low); splenic F4/80^-CD11b⁺Gr-1⁺ cells sorted from G-CSF-treated mice displayed higher levels of arginase-1, IL-10, and reactive oxygen species relative to those from control mice. Furthermore, these splenic cells effectively suppressed in vitro T cell activation mainly through arginase-1 and reactive oxygen species, and their adoptive transfer attenuated renal injury. Combined treatment with anti-Gr-1 and G-CSF showed better renoprotective effects than G-CSF alone, whereas preferential depletion of myeloid-derived suppressor cells by pep-G3 or gemcitabine abrogated the beneficial effects of G-CSF against renal injury.

CONCLUSIONS

G-CSF induced renal myeloid-derived suppressor cells, thereby attenuating acute renal injury and chronic renal fibrosis after ischemia-reperfusion injury. These results suggest therapeutic potential of myeloid-derived suppressor cells and G-CSF in renal ischemia-reperfusion injury.

Suppressor of cytokine signalling 3 is crucial for interleukin-7 receptor re-expression after T-cell activation and interleukin-7 dependent proliferation

SOCS3 is a crucial feedback inhibitor of several cytokine pathways with potential regulatory functions during T cell receptor activation. A role of SOCS3 in IL-7-dependent homeostatic mechanisms has been assumed but the underlying mechanisms remain unclear. We investigated the role of SOCS3 in IL-7 receptor α-chain (IL-7Rα) expression and IL-7 effects on activated human CD4⁺ T cells. SOCS3 expression modulation by lentiviral transduction combined with T cell phenotyping, receptor signalling analysis, and a novel competitive in vitro assay were applied. Time course analyses following T-cell activation showed IL-7Rα re-expression after initial down-regulation that was accompanied by increased SOCS3 expression starting on day 2. T cells with low SOCS3 expression (SOCS3_kd ) had decreased IL-7Rα levels due to impaired re-expression. SOCS3 mediated effects on IL-7Rα were not affected by recombinant IL-7 or blocking of IL-2. We found no evidence for SOCS3 effects on IL7RA transcriptional regulation. Functionally, SOCS3_kd T cells showed decreased IL-7-dependent proliferation as compared to vector control T cells under competitive in vitro conditions. This impaired IL-7 response of SOCS3_kd T cells was accompanied by decreased STAT5 phosphorylation late during IL-7 signalling. We identified a novel SOCS3 function in IL-7Rα regulation during T-cell activation with crucial implications for IL-7-dependent mechanisms.

Interleukin-27 promotes CD8+ T cell reconstitution following antibody-mediated lymphoablation

Antibody-mediated lymphoablation is used in solid organ and stem cell transplantation and autoimmunity. Using murine anti-thymocyte globulin (mATG) in a mouse model of heart transplantation, we previously reported that the homeostatic recovery of CD8+ T cells requires help from depletion-resistant memory CD4+ T cells delivered through CD40-expressing B cells. This study investigated the mechanisms by which B cells mediate CD8+ T cell proliferation in lymphopenic hosts. While CD8+ T cell recovery required MHC class I expression in the host, the reconstitution occurred independently of MHC class I, MHC class II, or CD80/CD86 expression on B cells. mATG lymphoablation upregulated the B cell expression of several cytokine genes, including IL-15 and IL-27, in a CD4-dependent manner. Neither treatment with anti-CD122 mAb nor the use of IL-15Rα-/- recipients altered CD8+ T cell recovery after mATG treatment, indicating that IL-15 may be dispensable for T cell proliferation in our model. Instead, IL-27 neutralization or the use of IL-27Rα-/- CD8+ T cells inhibited CD8+ T cell proliferation and altered the phenotype and cytokine profile of reconstituted CD8+ T cells. Our findings uncover what we believe is a novel role of IL-27 in lymphopenia-induced CD8+ T cell proliferation and suggest that targeting B cell-derived cytokines may increase the efficacy of lymphoablation and improve transplant outcomes.

The PD-L1- and IL6-mediated dampening of the IL27/STAT1 anticancer responses are prevented by α-PD-L1 or α-IL6 antibodies

Interleukin-27 (IL27) is a type-I cytokine of the IL6/IL12 family and is predominantly secreted by activated macrophages and dendritic cells. We show that IL27 induces STAT factor phosphorylation in cancerous cell lines of different tissue origin. IL27 leads to STAT1 phosphorylation and recapitulates an IFN-γ-like response in the microarray analyses, with up-regulation of genes involved in antiviral defense, antigen presentation, and immune suppression. Like IFN-γ, IL27 leads to an up-regulation of TAP2 and MHC-I proteins, which mediate increased tumor immune clearance. However, both cytokines also upregulate proteins such as PD-L1 (CD274) and IDO-1, which are associated with immune escape of cancer. Interestingly, differential expression of these genes was observed within the different cell lines and when comparing IL27 to IFN-γ. In coculture experiments of hepatocellular carcinoma (HCC) cells with peripheral blood mononuclear cells, pre-treatment of the HCC cells with IL27 resulted in lowered IL2 production by anti-CD3/-CD28 activated T-lymphocytes. Addition of anti-PD-L1 antibody, however, restored IL2 secretion. The levels of other T_H 1 cytokines were also enhanced or restored upon administration of anti-PD-L1. In addition, we show that the suppression of IL27 signaling by IL6-type cytokine pre-stimulation-mimicking a situation occurring, for example, in IL6-secreting tumors or in tumor inflammation-induced cachexia-can be antagonized by antibodies against IL6-type cytokines or their receptors. Therapeutically, the antitumor effects of IL27 (mediated, e.g., by increased antigen presentation) might thus be increased by combining IL27 with blocking antibodies against PD-L1 or/and IL6-type cytokines.

Lentivirus-mediated overexpression of suppressor of cytokine signaling-3 reduces neutrophilic airway inflammation by suppressing T-helper 17 responses in mice with chronic Pseudomonas aeruginosa lung infections

The aim of the present study was to explore the effect of overexpressed suppressor of cytokine signaling‑3 (SOCS3) on T-helper (Th)17 cell responses and neutrophilic airway inflammation in mice with chronic Pseudomonas aeruginosa (PA) infections. SOCS3 expression was enhanced via the administration of tail vein injections of therapeutic lentivirus in mice with chronic PA lung infections. SOCS3 expression in the blood and lung tissue was assessed using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analysis. Total and differential cell numbers and myeloperoxidase levels in the bronchoalveolar lavage (BAL) fluid were assessed, as well as the number of bacterial colonies in the lungs. Histological analysis of lung tissue was performed using hematoxylin and eosin staining and phosphorylated‑signal transducer and activator of transcription‑3 (p‑STAT3) expression was measured by western blot analysis and immunohistochemistry. The expression of STAT3 mRNA and retinoid‑related orphan receptor (ROR)γt were measured by RT‑qPCR. The percentage of interleukin (IL)‑17+ cells among cluster of differentiation (CD)4+ cells was calculated using flow cytometry and levels of IL‑17A and IL‑6 were assessed by ELISA. The expression of SOCS3 was significantly increased in CD4+ T cells following lentivirus injection and the inflammation of neutrophilic airways was notably ameliorated. Enhanced SOCS3 expression was associated with a significant decrease in the expression of p‑STAT3 and RORγt in CD4+ T cells. Additionally, the percentage of IL‑17+ cells among CD4+ T cells and the IL‑17 contents in the BAL fluid were significantly decreased. Lentivirus‑mediated overexpression of SOCS3 was revealed to ameliorate neutrophilic airway inflammation by inhibiting pulmonary Th17 responses in mice with chronic PA lung infections.

Interaction of suppressor of cytokine signalling 3 with cavin-1 links SOCS3 function and cavin-1 stability

Effective suppression of JAK-STAT signalling by the inducible inhibitor "suppressor of cytokine signalling 3" (SOCS3) is essential for limiting signalling from cytokine receptors. Here we show that cavin-1, a component of caveolae, is a functionally significant SOCS3-interacting protein. Biochemical and confocal imaging demonstrate that SOCS3 localisation to the plasma membrane requires cavin-1. SOCS3 is also critical for cavin-1 stabilisation, such that deletion of SOCS3 reduces the expression of cavin-1 and caveolin-1 proteins, thereby reducing caveola abundance in endothelial cells. Moreover, the interaction of cavin-1 and SOCS3 is essential for SOCS3 function, as loss of cavin-1 enhances cytokine-stimulated STAT3 phosphorylation and abolishes SOCS3-dependent inhibition of IL-6 signalling by cyclic AMP. Together, these findings reveal a new functionally important mechanism linking SOCS3-mediated inhibition of cytokine signalling to localisation at the plasma membrane via interaction with and stabilisation of cavin-1.

IL-27 enhances LPS-induced IL-1β in human monocytes and murine macrophages

IL-27 bridges innate and adaptive immunity by modulating cytokine production from myeloid cells and regulating Th cell differentiation. During bacterial infection, TLR4 triggering by LPS induces IL-27 production by monocytes and macrophages. We have previously shown that IL-27 can prime monocytes for LPS responsiveness by enhancing TLR4 expression and intracellular signaling. If unregulated, this could result in damaging inflammation, whereas on the other hand, this may also provide greater responses by inflammatory processes induced in response to bacterial pathogens. A key process in fine-tuning inflammatory responses is activation of the inflammasome, which ultimately results in IL-1β production. Herein, we investigated the molecular mechanisms by which IL-27 modulates LPS-induced IL-1β secretion in monocytes and macrophages. We found that when delivered simultaneously with LPS, IL-27 augments activation of caspase-1 and subsequent release of IL-1β. Furthermore, we determined that IL-27 primes cells for enhanced IL-1β production by up-regulating surface expression of TLR4 and P2X purinoceptor 7 (P2X7) for enhanced LPS and ATP signaling, respectively. These findings provide new evidence that IL-27 plays an important role in the proinflammatory capacity of monocytes and macrophages via enhancing IL-1β secretion levels triggered by dual LPS-ATP stimulation.

Dual Roles of IL-27 in Cancer Biology and Immunotherapy

IL-27 is a pleiotropic two-chain cytokine, composed of EBI3 and IL-27p28 subunits, which is structurally related to both IL-12 and IL-6 cytokine families. IL-27 acts through a heterodimer receptor consisting of IL-27Rα (WSX1) and gp130 chains, which mediate signaling predominantly through STAT1 and STAT3. IL-27 was initially reported as an immune-enhancing cytokine that supports CD4+ T cell proliferation, T helper (Th)1 cell differentiation, and IFN-γ production, acting in concert with IL-12. However, subsequent studies demonstrated that IL-27 displays complex immune-regulatory functions, which may result in either proinflammatory or anti-inflammatory effects in relationship to the biological context and experimental models considered. Several pieces of evidence, obtained in preclinical tumor models, indicated that IL-27 has a potent antitumor activity, related not only to the induction of tumor-specific Th1 and cytotoxic T lymphocyte (CTL) responses but also to direct inhibitory effects on tumor cell proliferation, survival, invasiveness, and angiogenic potential. Nonetheless, given its immune-regulatory functions, the effects of IL-27 on cancer may be dual and protumor effects may also occur. Here, we will summarize IL-27 biological activities and its functional overlaps with the IFNs and discuss its dual role in tumors in the light of potential applications to cancer immunotherapy.

Impact of Enriched Environment on Murine T Cell Differentiation and Gene Expression Profile

T cells are known to be plastic and to change their phenotype according to the cellular and biochemical milieu they are embedded in. In this study, we transposed this concept at a macroscopic level assessing whether changes in the environmental housing conditions of C57/BL6 mice would influence the phenotype and function of T cells. Our study shows that exposure to 2 weeks in an enriched environment (EE) does not impact the T cell repertoire in vivo and causes no changes in the early TCR-driven activation events of these cells. Surprisingly, however, T cells from enriched mice showed a unique T helper effector cell phenotype upon differentiation in vitro. This was featured by a significant reduction in their ability to produce IFN-γ and by an increased release of IL-10 and IL-17. Microarray analysis of these cells also revealed a unique gene fingerprint with key signaling pathways involved in autoimmunity being modulated. Together, our results provide first evidence for a specific effect of EE on T cell differentiation and its associated changes in gene expression profile. In addition, our study sheds new light on the possible mechanisms by which changes in environmental factors can significantly influence the immune response of the host and favor the resolution of the inflammatory response.

Potential roles of suppressor of cytokine signaling in wound healing

Wound healing is a dynamic process comprising three overlapping, highly orchestrated stages known as inflammation, proliferation and re-epithelialization, and tissue remodeling. This complex process is regulated by numerous cytokines, with dysregulation of cytokine-induced signaling leading to impaired wound healing. Suppressor of cytokine signaling (SOCS) proteins are a family of eight intracellular proteins which may hold the potential to maintain homeostasis during wound healing through their negative feedback inhibition of cytokine signaling. To date, the roles of SOCS proteins in inflammation, autoimmunity and cancer have been comprehensively illustrated; however, only a limited number of studies focused on their role in wound healing. This review demonstrates the possible links between SOCS proteins and wound healing, and also highlights the potential importance of this family in a variety of other aspects of regenerative medicine.

A novel role for histone deacetylase 6 in the regulation of the tolerogenic STAT3/IL-10 pathway in APCs

APCs are critical in T cell activation and in the induction of T cell tolerance. Epigenetic modifications of specific genes in the APC play a key role in this process, and among them histone deacetylases (HDACs) have emerged as key participants. HDAC6, one of the members of this family of enzymes, has been shown to be involved in regulation of inflammatory and immune responses. In this study, to our knowledge we show for the first time that genetic or pharmacologic disruption of HDAC6 in macrophages and dendritic cells results in diminished production of the immunosuppressive cytokine IL-10 and induction of inflammatory APCs that effectively activate Ag-specific naive T cells and restore the responsiveness of anergic CD4(+) T cells. Mechanistically, we have found that HDAC6 forms a previously unknown molecular complex with STAT3, association that was detected in both the cytoplasmic and nuclear compartments of the APC. By using HDAC6 recombinant mutants we identified the domain comprising amino acids 503-840 as being required for HDAC6 interaction with STAT3. Furthermore, by re-chromatin immunoprecipitation we confirmed that HDAC6 and STAT3 are both recruited to the same DNA sequence within the Il10 gene promoter. Of note, disruption of this complex by knocking down HDAC6 resulted in decreased STAT3 phosphorylation--but no changes in STAT3 acetylation--as well as diminished recruitment of STAT3 to the Il10 gene promoter region. The additional demonstration that a selective HDAC6 inhibitor disrupts this STAT3/IL-10 tolerogenic axis points to HDAC6 as a novel molecular target in APCs to overcome immune tolerance and tips the balance toward T cell immunity.

Suppressor of cytokine signalling (SOCS) proteins as guardians of inflammatory responses critical for regulating insulin sensitivity

Overactivation of immune pathways in obesity is an important cause of insulin resistance and thus new approaches aimed to limit inflammation or its consequences may be effective for treating Type 2 diabetes. The SOCS (suppressors of cytokine signalling) are a family of proteins that play an essential role in mediating inflammatory responses in both immune cells and metabolic organs such as the liver, adipose tissue and skeletal muscle. In the present review we discuss the role of SOCS1 and SOCS3 in controlling immune cells such as macrophages and T-cells and the impact this can have on systemic inflammation and insulin resistance. We also dissect the mechanisms by which SOCS (1-7) regulate insulin signalling in different tissues including their impact on the insulin receptor and insulin receptor substrates. Lastly, we discuss the important findings from SOCS whole-body and tissue-specific null mice, which implicate an important role for these proteins in controlling insulin action and glucose homoeostasis in obesity.

Dynamic expression of the suppressor of cytokine signaling-3 and cytokines in the cerebral basilar artery of rats with subarachnoid hemorrhage, and the effect of acetylcholine

BACKGROUND

There are complex interactions between acetylcholine (ACh), the suppressor of cytokine signaling-3 (SOCS-3), and cytokines, however, little is known about their dynamic expression or their effects on cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH). Therefore, we aimed to describe and clarify the dynamic expression of SOCS-3 and cytokines after SAH, as well as the relationships between the levels of SOCS-3, cytokines, and ACh.

METHODS

The rat model of single cisterna magna injection was used to mimic acute SAH. The degree of CVS was indicated by lumen diameter and artery wall thickness under H&E staining. A semi-quantitative immunohistochemical analysis method was used to clarify the role of SOCS-3 in the CVS after SAH. We also measured the content of IL-6 and IL-10 in cerebrospinal fluid.

RESULTS

We found that SOCS-3 expression levels increased rapidly within 12 h after SAH, more slowly after 12 h, and did not reach a peak within 48 h. Interleukin 6 (IL-6) levels rapidly increased within 24 h after SAH, reached a peak 24 h after SAH, and decreased slightly at 48 h. IL-10 levels increased during the first 6 h after SAH, after which this increase tapered off. ACh treatment reduced IL-6 levels and resulted in elevated levels of SOCS-3, but had no effect on IL-10 expression. Furthermore, ACh treatment relieved basilar arterial vasospasm, whereas mecamylamine pretreatment counteracted the activity of ACh.

CONCLUSIONS

Taken together, these data indicate that SOCS-3 was involved in vasospasm via an IL-6- and IL-10-related mechanism, and that CVS following SAH could be reversed by the intraventricular injection of ACh.

The role of suppressors of cytokine signalling in human neoplasms

Suppressors of cytokine signalling 1-7 (SOCS1-7) and cytokine-inducible SH2-containing protein (CIS) are a group of intracellular proteins that are well known as JAK-STAT and several other signalling pathways negative feedback regulators. More recently several members have been identified as tumour suppressors and dysregulation of their biological roles in controlling cytokine and growth factor signalling may contribute to the development of many solid organ and haematological malignancies. This review explores their biological functions and their possible tumour suppressing role in human neoplasms.

SOCS3, a Major Regulator of Infection and Inflammation

In this review, we describe the role of suppressor of cytokine signaling-3 (SOCS3) in modulating the outcome of infections and autoimmune diseases as well as the underlying mechanisms. SOCS3 regulates cytokine or hormone signaling usually preventing, but in some cases aggravating, a variety of diseases. A main role of SOCS3 results from its binding to both the JAK kinase and the cytokine receptor, which results in the inhibition of STAT3 activation. Available data also indicate that SOCS3 can regulate signaling via other STATs than STAT3 and also controls cellular pathways unrelated to STAT activation. SOCS3 might either act directly by hampering JAK activation or by mediating the ubiquitination and subsequent proteasome degradation of the cytokine/growth factor/hormone receptor. Inflammation and infection stimulate SOCS3 expression in different myeloid and lymphoid cell populations as well as in diverse non-hematopoietic cells. The accumulated data suggest a relevant program coordinated by SOCS3 in different cell populations, devoted to the control of immune homeostasis in physiological and pathological conditions such as infection and autoimmunity.

Suppression of cytokine signaling: the SOCS perspective

The discovery of the Suppressor of Cytokine Signaling (SOCS) family of proteins has resulted in a significant body of research dedicated to dissecting their biological functions and the molecular mechanisms by which they achieve potent and specific inhibition of cytokine and growth factor signaling. The Australian contribution to this field has been substantial, with the initial discovery of SOCS1 by Hilton, Starr and colleagues (discovered concurrently by two other groups) and the following work, providing a new perspective on the regulation of JAK/STAT signaling. In this review, we reflect on the critical discoveries that have lead to our current understanding of how SOCS proteins function and discuss what we see as important questions for future research.

IL-27 suppresses the production of IL-22 in human CD4(+) T cells by inducing the expression of SOCS1

IL-27, a member of IL-6/IL-12 cytokine family, plays pro- and anti-inflammatory functions in immune responses. It can promote inflammation by inducing Th1 differentiation and exert the inhibitory effects on Th2 and Th17 mediated immune responses. Moreover, IL-27 suppresses CD28-mediated IL-2 production from mouse naive CD4(+) T cells. In the present study, we demonstrate that IL-27 inhibits the production of IL-22 and induces the expression of IFN-γ in CD4(+) T cells from human umbilical cord blood mononuclear cells (CBMCs) stimulated with anti-CD3 and anti-CD28 in dose-dependent manner. In addition, the suppression of IL-22 is not dependent on the production of IFN-γ and IL-10. Importantly, IL-27 promotes the expression of SOCS1, which could be inhibited by a Jak2/STAT inhibitor, AG490. Importantly, the expression of IL-22 could not be inhibited under the circumstances with the lower expression of SOCS1. Moreover, IL-27 inhibits the production of IL-22 in CD4(+)CD45RA(+) and CD4(+)CD45RO(+) T cells from PBMCs. These data identify that IL-27 may suppress the production of IL-22 by inducing the expression of SOCS1 in human CD4(+) T cells. Furthermore, it demonstrates that IL-27 may be a therapeutic approach in the treatment of IL-22-mediated diseases.

Murine dendritic cell rapamycin-resistant and rictor-independent mTOR controls IL-10, B7-H1, and regulatory T-cell induction

Mammalian target of rapamycin (mTOR) is an important, yet poorly understood integrative kinase that regulates immune cell function. mTOR functions in 2 independent complexes: mTOR complex (mTORC) 1 and 2. The immunosuppressant rapamycin (RAPA) inhibits mTORC1 but not mTORC2 and causes a paradoxical reduction in anti-inflammatory interleukin (IL) 10 and B7-homolog 1 (B7-H1) expression by dendritic cells (DCs). Using catalytic mTOR inhibitors and DCs lacking mTORC2, we show that restraint of signal transducer and activator of transcription 3-mediated IL-10 and B7-H1 expression during DC maturation involves a RAPA-insensitive and mTORC2-independent mTOR mechanism. Relatedly, catalytic mTOR inhibition promotes B7-H1-dependent and IL-1β-dependent DC induction of regulatory T cells (Tregs). Thus, we define an immunoregulatory pathway in which RAPA-sensitive mTORC1 in DCs promotes effector T-cell expansion and RAPA-insensitive mTORC1 restrains T(reg) induction. These findings identify the first known RAPA-insensitive mTOR pathway that is not mediated solely by mTORC2 and have implications for the use of catalytic mTOR inhibitors in inflammatory disease settings.

SOCS3 promotes interleukin-17 expression of human T cells

SOCS3 is a feedback regulator of cytokine signaling that affects T-cell polarization. Human tuberculosis is accompanied by increased SOCS3 expression in T cells, and this may influence susceptibility against Mycobacterium tuberculosis. Because the role of SOCS3 in human T-cell function is not well defined, we characterized cytokine expression and proliferation of human T cells with differential SOCS3 expression in the present study. We established a flow cytometry–based method for SOCS3 protein quantification and detected higher SOCS3 levels induced by M tuberculosis specific T-cell activation and a transient decrease of SOCS3 expression in the presence of mycobacteria-infected macrophages. Notably increased SOCS3 expression was detected in IL-17–expressing T-cell clones and in CD161+ T helper type 17 cells ex vivo. Ectopic SOCS3 expression in primary CD4+ T cells by lentiviral transduction induced increased IL-17 production but diminished proliferation and viability. Recombinant IL-7 inhibited SOCS3 expression and reduced IL-17–expressing T-cell proportions. We concluded that higher SOCS3 expression in human T cells favors T helper type 17 cells. Therefore, increased SOCS3 expression in human tuberculosis may reflect polarization toward IL-17–expressing T cells as well as T-cell exhaustion marked by reduced proliferation.

The biology and mechanism of action of suppressor of cytokine signaling 3

Suppressors of cytokine signaling 3 (SOCS3) has been shown to be an important and non-redundant feedback inhibitor of several cytokines including leukemia inhibitory factor, IL-6, IL-11, Ciliary neurotrophic factor (CNTF), leptin, and granulocyte colony-stimulating factor (G-CSF). Loss of SOCS3 in vivo has profound effects on placental development, inflammation, fat-induced weight gain, and insulin sensitivity. SOCS3 expression is induced by Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling and it then binds to specific cytokine receptors (including gp130, G-CSF, and leptin receptors). SOCS3 then inhibits JAK/STAT signaling in two distinct ways. First, SOCS3 is able to directly inhibit the catalytic activity of JAK1, JAK2, or TYK2 while remaining bound to the cytokine receptor. Second, SOCS3 recruits elongins B/C and Cullin5 to generate an E3 ligase that ubiquitinates both JAK and cytokine receptor targeting them for proteasomal degradation. Detailed in vivo studies have revealed that SOCS3 action not only limits the duration of cytokine signaling to prevent overactivity but it is also important in maintaining the specificity of cytokine signaling.

Interleukin-27 and interleukin-12 augment activation of distinct cord blood natural killer cells responses via STAT3 pathways

BACKGROUND/PURPOSE

Umbilical cord blood is rich in primitive natural killer (NK) cells, which are activated by interleukin (IL)-12. It was previously reported that a novel IL-12 family cytokine, IL-27 comprised of EBI3 and p28, was elevated in maternal serum during normal pregnancy. Thus, we compared the immune regulatory functions of IL-27 and IL-12 on mononuclear cells derived from cord blood and adult peripheral blood.

METHODS

After stimulation with IL-27, IL-12, and IL-27 combined with IL-12, the cytotoxicity against BJAB lymphoma cells by blood mononuclear cells was performed. Then immunofluorescence staining, reverse transcriptase-polymerase chain reaction and Western blotting were used to detect the effects of IL-27 and IL-12 in isolated NK cells.

RESULTS

IL-27, IL-12, and IL-27 combined with IL-12 enhanced the cytotoxicity of adult peripheral blood cells and cord blood cells, but the proliferation of distinct subpopulations of cells was not evident. Similar results were also obtained with purified cord blood NK cells. Interestingly, distinct from IL-12, IL-27 could induce aggregation and morphological changes of umbilical cord blood cells. Finally, IL-27 combined with IL-12 could stimulate increased IL-27 receptor (gp130 and WSX-1) transcripts in purified cord blood NK cells. However, the activation of signal transducer and activator of transcription 3 (STAT3) in NK cells was only detected in the presence of IL-27, but not IL-12 alone.

CONCLUSION

From previous results, we summarize our current understanding of the augmentation of distinct regulation of NK cells by IL-27 and IL-12.

Interpreting mixed signals: the cell's cytokine conundrum

Cytokines are essential for the activation, differentiation and control of the immune system. Many cytokines, alone or in combination with other cytokines, have multiple functions and can often act on many different cell types with distinct developmental or functional consequences. Despite the myriad of cytokines and cytokine receptors, there are relatively few signaling molecules that transduce these diverse cytokine signals. In this review, we will discuss the potential mechanisms used by cytokines to mediate distinct cellular outcomes from a small number of signaling molecules. Understanding this paradigm in cytokine signaling can aid in the development of potential therapeutic approaches involving cytokine targeting or use.

Signaling events involved in interleukin 27 (IL-27)-induced proliferation of human naive CD4+ T cells and B cells

IL-27 induces stronger proliferation of naive than memory human B cells and CD4(+) T cells. In B cells, this differential response is associated with similar levels of IL-27 receptor chains, IL-27Rα and gp130, in both subsets and stronger STAT1 and STAT3 activation by IL-27 in naive B cells. Here, we show that the stronger proliferative response of CD3-stimulated naive CD4(+) T cells to IL-27 is associated with lower levels of IL-27Rα but higher levels of gp130 compared with memory CD4(+) T cells. IL-27 signaling differs between naive and memory CD4(+) T cells, as shown by more sustained STAT1, -3, and -5 activation and weaker activation of SHP-2 in naive CD4(+) T cells. In the latter, IL-27 increases G0/G1 to S phase transition, cell division and, in some cases, cell survival. IL-27 proliferative effect on naive CD4(+) T cells is independent of MAPK, but is dependent on c-Myc and Pim-1 induction by IL-27 and is associated with induction of cyclin D2, cyclin D3, and CDK4 by IL-27 in a c-Myc and Pim-1-dependent manner. In BCR-stimulated naive B cells, IL-27 only increases entry in the S phase and induces the expression of Pim-1 and of cyclins A, D2, and D3. In these cells, inhibition of Pim-1 inhibits IL-27 effect on proliferation and cyclin induction. Altogether, these data indicate that IL-27 mediates proliferation of naive CD4(+) T cells and B cells through induction of both common and distinct sets of cell cycle regulators.

IL-7 engages multiple mechanisms to overcome chronic viral infection and limit organ pathology

Understanding the factors that impede immune responses to persistent viruses is essential in designing therapies for HIV infection. Mice infected with LCMV clone-13 have persistent high-level viremia and a dysfunctional immune response. Interleukin-7, a cytokine that is critical for immune development and homeostasis, was used here to promote immunity toward clone-13, enabling elucidation of the inhibitory pathways underlying impaired antiviral immune response. Mechanistically, IL-7 downregulated a critical repressor of cytokine signaling, Socs3, resulting in amplified cytokine production, increased T cell effector function and numbers, and viral clearance. IL-7 enhanced thymic output to expand the naive T cell pool, including T cells that were not LCMV specific. Additionally, IL-7 promoted production of cytoprotective IL-22 that abrogated liver pathology. The IL-7-mediated effects were dependent on endogenous IL-6. These attributes of IL-7 have profound implications for its use as a therapeutic in the treatment of chronic viral diseases.

Suppressor of cytokine signaling-3 is affected in T-cells from tuberculosisTB patients

T-cells and T-cell-derived cytokines are crucial mediators of protection against Mycobacterium tuberculosis infection, but these factors are insufficient as biomarkers for disease susceptibility. In order to define T-cell molecules involved in tuberculosis (TB), we compared gene expression profiles of T-cells from patients with active TB, healthy donors with latent M. tuberculosis infection (LTBIs) and non-infected healthy donors (NIDs) by microarray analysis. Pathway-focused analyses identified a prevalent subset of candidate genes involved in the Janus kinase (JAK)-signal transducer and activator of transcription signalling pathway, including those encoding suppressor of cytokine signalling (SOCS) molecules, in the subset of protection-associated genes. Differential expression was verified by quantitative PCR analysis for the cytokine-inducible SH2-containing protein (CISH), SOCS3, JAK3, interleukin-2 receptor α-chain (IL2RA), and the proto-oncogene serine/threonine protein kinase (PIM1). Classification analyses revealed that this set of molecules was able to discriminate efficiently between T-cells from TB patients and those from LTBIs, and, notably, to achieve optimal discrimination between LTBIs and NIDs. Further characterization by quantitative PCR revealed highly variable candidate gene expression in CD4(+) and CD8(+) T-cells from TB patients and only minor differences between CD4(+) and CD8(+) T-cell subpopulations. These results point to a role of cytokine receptor signalling regulation in T-cells in susceptibility to TB.

Immunomodulatory effects of lenalidomide and pomalidomide on interaction of tumor and bone marrow accessory cells in multiple myeloma

The bone marrow (BM) microenvironment consists of extracellular-matrix and the cellular compartment including immune cells. Multiple myeloma (MM) cell and BM accessory cell interaction promotes MM survival via both cell-cell contact and cytokines. Immunomodulatory agents (IMiDs) target not only MM cells, but also MM cell-immune cell interactions and cytokine signaling. Here we examined the in vitro effects of IMiDs on cytokine signaling triggered by interaction of effector cells with MM cells and BM stroma cells. IMiDs diminished interleukin-2, interferonγ, and IL-6 regulator suppressor of cytokine signaling (SOCS)1 expression in immune (CD4T, CD8T, natural-killer T, natural-killer) cells from both BM and PB of MM patients. In addition, coculture of MM cells with healthy PBMCs induced SOCS1 expression in effector cells; conversely, treatment with IMiDs down-regulated the SOCS1 expression. SOCS1 negatively regulates IL-6 signaling and is silenced by hypermethylation in MM cells. To define the mechanism of inhibitory-cytokine signaling in effector cells and MM cells, we next analyzed the interaction of immune cells with MM cells that were epigenetically modified to re-express SOCS1; IMiDs induced more potent CTL responses against SOCS1 re-expressing-MM cells than unmodified MM cells. These data therefore demonstrate that modulation of SOCS1 may enhance immune response and efficacy of IMiDs in MM.

T cell treatment with small interfering RNA for suppressor of cytokine signaling 3 modulates allergic airway responses in a murine model of asthma

CD4(+) T cells, particularly T helper (Th) 2 cells, play a pivotal role in the pathophysiology of allergic asthma. Suppressor of cytokine signaling (SOCS) proteins control the balance of CD4(+) T cell differentiation. Mice that lack SOCS3 in T cells by crossing SOCS3-floxed mice with Lck-Cre-transgenic mice have reduced allergen-induced eosinophilia in the airways. Here, we studied the effects of SOCS3 silencing with small interfering (si) RNA in primary CD4(+) T cells on Th2 cell differentiation and on asthmatic responses in mice. Th2 cells were generated from ovalbumin (OVA)-specific T cell receptor-transgenic mice in vitro and transferred into recipient mice. Transfection of SOCS3-specific siRNA attenuated Th2 response in vitro. Adoptive transfer of SOCS3-siRNA T cells exhibited markedly suppressed airway hyperresponsiveness and eosinophilia after OVA challenge, with a concomitant decrease in OVA-specific CD4(+) T cell accumulation in the airways. To investigate the mechanism of this impaired CD4(+) T cell accumulation, we inactivated SOCS3 of T cells by crossing SOCS3-floxed (SOCS3(flox/flox)) mice with CD4-Cre transgenic mice. CD4-Cre × SOCS3(flox/flox) mice exhibited fewer IL-4-producing cells and more reduced eosinophil infiltration in bronchoalveolar lavage fluids than control mice in a model of OVA-induced asthma. Expression of CCR3 and CCR4 in CD4(+) T cells was decreased in CD4-Cre × SOCS3(flox/flox) mice. CCR4 expression was also decreased in CD4(+) T cells after transfer of SOCS3 siRNA-treated T cells. These findings suggest that the therapeutic modulation of SOCS3 expression in CD4(+) T cells might be effective in preventing the development of allergic asthma.

SOCS3 regulates graft-versus-host disease

Suppressor of cytokine signaling-3 (SOCS3) is the main intracellular regulator of signaling by granulocyte colony-stimulating factor, an immune-modulatory cytokine used to mobilize stem cells for transplantation. We have therefore studied the contribution of SOCS3 to the spectrum of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (SCT). Grafts from SOCS3(-/Deltavav) donor mice in which SOCS3 deficiency is restricted to the hematopoietic compartment had an augmented capacity to induce acute GVHD. With the use of SOCS3(-/DeltaLysM) and SOCS3(-/Deltalck) donors in which SOCS3 deficiency was restricted to the myeloid or T-cell lineage, respectively, we confirmed SOCS3 deficiency promoted acute GVHD mortality and histopathology within the gastrointestinal tract by effects solely within the donor T cell. SOCS3(-/Deltalck) donor T cells underwent enhanced alloantigen-dependent proliferation and generation of interleukin-10 (IL-10), IL-17, and interferon-gamma (IFNgamma) after SCT. The enhanced capacity of the SOCS3(-/Deltalck) donor T cell to induce acute GVHD was dependent on IFNgamma but independent of IL-10 or IL-17. Surprisingly, SOCS3(-/Deltalck) donor T cells also induced severe, transforming growth factor beta- and IFNgamma-dependent, sclerodermatous GVHD. Thus, the delivery of small molecule SOCS3 mimetics may prove to be useful for the inhibition of both acute and chronic GVHD.

A pivotal role for interleukin-27 in CD8+ T cell functions and generation of cytotoxic T lymphocytes

Cytotoxic T lymphocytes (CTLs) play a critical role in the control of various cancers and infections, and therefore the molecular mechanisms of CTL generation are a critical issue in designing antitumor immunotherapy and vaccines which augment the development of functional and long-lasting memory CTLs. Interleukin (IL)-27, a member of the IL-6/IL-12 heterodimeric cytokine family, acts on naive CD4+ T cells and plays pivotal roles as a proinflammatory cytokine to promote the early initiation of type-1 helper differentiation and also as an antiinflammatory cytokine to limit the T cell hyperactivity and production of pro-inflammatory cytokines. Recent studies revealed that IL-27 plays an important role in CD8+ T cells as well. Therefore, this article reviews current understanding of the role of IL-27 in CD8+ T cell functions and generation of CTLs.

Interleukin-2 inhibits polarization to T helper type 1 cells and prevents mouse acute graft-versus-host disease through up-regulating suppressors of cytokine signalling-3 expression of naive CD4+ T cells

T helper type 1 (Th1)-type polarization plays a critical role in the pathophysiology of acute graft-versus-host disease (aGVHD). The differentiation of T cells into this subtype is dictated by the nature of the donor naive CD4(+) T cell-host antigen presenting cell (APC) interaction. Suppressors of cytokine signalling (SOCS) are a family of molecules that act as negative regulators for cytokine signalling, which regulate the negative cytokine signalling pathway through inhibiting the cytokine-induced Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. Studies have shown that SOCS proteins are key physiological regulators of both innate and adaptive immunity. These molecules are essential for T cell development and differentiation. SOCS-3 can inhibit polarization to Th1 and contribute to polarization to Th2. In this study, we found that interleukin (IL)-2 pre-incubation of C57BL/6 naive CD4(+) T cells could up-regulate the expression of SOCS-3. Naive CD4(+) T cells constitutively expressed low levels of SOCS-3 mRNA. SOCS-3 mRNA began to rise after 4 h, and reached peak level at 6 h. At 8 h it began to decrease. High expression of SOCS-3 mRNA induced by IL-2 could inhibit the proliferation of naive CD4(+) T cells following stimulation with allogeneic antigen. IL-2-induced high SOCS-3 expression in naive CD4(+) T cells could inhibit polarization to Th1 with stimulation of allogeneic antigens. We have demonstrated that IL-2-induced high SOCS-3 expression in naive CD4(+) T cells could reduce the incidence of aGVHD between major histocompatibility complex (MHC) completely mismatched donor and host when high SOCS3 expression of CD4(+)T cells encounter allogeneic antigen in time. These results show that IL-2-induced high SOCS-3 expression can inhibit aGVHD through inhibiting proliferation and polarization to Th1 with the stimulation of allogeneic antigen.

Suppressors of cytokine signaling (SOCS) in T cell differentiation, maturation, and function

Cytokines are key modulators of T cell biology, but their influence can be attenuated by suppressors of cytokine signaling (SOCS), a family of proteins consisting of eight members, SOCS1-7 and CIS. SOCS proteins regulate cytokine signals that control the polarization of CD4(+) T cells into Th1, Th2, Th17, and T regulatory cell lineages, the maturation of CD8(+) T cells from naïve to "stem-cell memory" (Tscm), central memory (Tcm), and effector memory (Tem) states, and the activation of these lymphocytes. Understanding how SOCS family members regulate T cell maturation, differentiation, and function might prove critical in improving adoptive immunotherapy for cancer and therapies aimed at treating autoimmune and infectious diseases.

Epigenetic alteration of SOCS family members is a possible pathogenetic mechanism in JAK2 wild type myeloproliferative diseases

In polycythemia vera (PV) and essential thrombocythemia (ET) specific JAK2 mutations constitutively activate the JAK-STAT pathway, explaining biologic findings such as endogenous erythroid colony (EECs) growth or PRV-1 RNA overexpression. Since these markers are detected also in JAK2 wild type patients, we hypothesized that, in these cases, the activation of the JAK-STAT pathway could be produced by a deregulation of the suppressor of cytokine signaling (SOCS) protein system. Eighty-one patients with PV and ET (53 adults and 28 children) were investigated for the methylation status of the SOCS-1, SOCS-2 and SOCS-3 CpG islands and for several myeloproliferative markers (including JAK2 and MPL mutations and clonality of hematopoiesis). SOCS-1 or SOCS-3 hypermethylation was identified in 23 patients and was associated with a significant decrease of SOCS-1 or SOCS-3 RNA and protein levels. The gene expression was restored by exposing cells to the demethylating agent 2-deoxyazacytidin. Interestingly, SOCS-1 or SOCS-3 hypermethylation was detected in 6 female patients, proved negative for JAK2 or MPL mutations and exhibiting monoclonal hematopoiesis. In conclusion, SOCS-1 or SOCS-3 hypermethylation can activate the JAK-STAT signaling pathway in alternative or together with JAK2 mutations. These alterations might represent a potential therapeutic target.

STAT3 is indispensable to IL-27-mediated cell proliferation but not to IL-27-induced Th1 differentiation and suppression of proinflammatory cytokine production

IL-27, a member of the IL-6/IL-12 family, activates both STAT1 and STAT3 through its receptor, which consists of WSX-1 and gp130 subunits, resulting in augmentation of Th1 differentiation and suppression of proinflammatory cytokine production. In the present study, we investigated the role of STAT3 in the IL-27-mediated immune functions. IL-27 induced phosphorylation of STAT1, -2, -3 and -5 in wild-type naive CD4+ T cells, but failed to induce that of STAT3 and STAT5 in STAT3-deficient cohorts. IL-27 induced not only proinflammatory responses including up-regulation of ICAM-1, T-box expressed in T cells, and IL-12Rbeta2 and Th1 differentiation, but also anti-inflammatory responses including suppression of proinflammatory cytokine production such as IL-2, IL-4, and IL-13 even in STAT3-deficient naive CD4+ T cells. In contrast, IL-27 augmented c-Myc and Pim-1 expression and induced cell proliferation in wild-type naive CD4+ T cells but not in STAT3-deficient cohorts. Moreover, IL-27 failed to activate STAT3, augment c-Myc and Pim-1 expression, and induce cell proliferation in pro-B BaF/3 transfectants expressing mutant gp130, in which the putative STAT3-binding four Tyr residues in the YXXQ motif of the cytoplasmic region was replaced by Phe. These results suggest that STAT3 is activated through gp130 by IL-27 and is indispensable to IL-27-mediated cell proliferation but not to IL-27-induced Th1 differentiation and suppression of proinflammatory cytokine production. Thus, IL-27 may be a cytokine, which activates both STAT1 and STAT3 through distinct receptor subunits, WSX-1 and gp130, respectively, to mediate its individual immune functions.

Perturbed thymopoiesis in vitro in the absence of suppressor of cytokine signalling 1 and 3

Cytokine signals are central to the differentiation of thymocytes and their stepwise progression through defined developmental stages. The intensity and duration of cytokine signals are regulated by the suppressor of cytokine signalling (SOCS) proteins. A clear role for SOCS1 during the later stages of thymopoiesis has been established, but little is known about its role during early thymopoiesis, nor the function of its closest relative, SOCS3. Here, we find that both SOCS1 and SOCS3 are expressed during early thymopoiesis, with expression coincident during the double negative (DN)2 and DN3 stages. We examined thymocyte differentiation in vitro by co-culture of SOCS-deficient bone marrow cells with OP9 cells expressing the Notch ligand Delta-like1 (OP9-DL1). Cells lacking SOCS1 were retarded at the DN3:DN4 transition and appeared unable to differentiate into double positive (DP) thymocytes. Cells lacking both SOCS1 and SOCS3 were more severely affected, and displayed an earlier block in T cell differentiation at DN2, the stage at which expression of SOCS1 and SOCS3 coincides. This indicates that, in addition to their specific roles, SOCS1 and SOCS3 share overlapping roles during thymopoiesis. This is the first demonstration of functional redundancy within the SOCS family, and has uncovered a vital role for SOCS1 and SOCS3 during two important checkpoints in early T cell development.