The Tim-3 ligand galectin-9 negatively regulates CD8+ alloreactive T cell and prolongs survival of skin graft

CD8+ alloreactive T cells are the key mediators of accelerated rejection. Vigorous CD8+ alloreactive T cells responses against alloantigens, which is the main effector mechanism in acute allograft rejection, has been well described. But the molecular mechanisms to dampen activated CD8+ T cells are largely unknown. On the other hand, Tim-3 is a molecule expressed on terminally differentiated CD4+ Th1 cells. Engaging Tim-3 with its ligand galectin-9 causes an inhibitory signal, resulting in apoptosis of Th1 cells and negatively regulates Th1 type immunity. However, the question whether CD8+ T cells express surface molecular Tim-3 has not been fully elucidated. In this study, we have investigated which CD8+ subset express molecular Tim-3 by flow cytometric assay. In addition, cytotoxic assay was applied to analyze whether CD8+ alloreactive T cells were sensitive to galectin-9 induced apoptosis. Here, our results demonstrated that Tim-3 was expressed on activated CD8+ alloreactive T cells (CD8+CD44highCD62Llow), but not expressed on na?ve CD8+ T cells. Furthermore, alloreactive CD8+ cytotoxic T cells were sensitive to galectin-9 induced apoptosis both in vitro and vivo, resulting in attenuation of CD8+ alloreactive T cells mediated cytotoxicity and prolonged survival of skin graft.     

Upregulation of the Tim-3/Galectin-9 Pathway of T Cell Exhaustion in Chronic Hepatitis B Virus Infection

The S-type lectin galectin-9 binds to the negative regulatory molecule Tim-3 on T cells and induces their apoptotic deletion or functional inactivation. We investigated whether galectin-9/Tim-3 interactions contribute to the deletion and exhaustion of the antiviral T cell response in chronic hepatitis B virus infection (CHB). We found Tim-3 to be expressed on a higher percentage of CD4 and CD8 T cells from patients with CHB than healthy controls (p<0.0001) and to be enriched on activated T cells and those infiltrating the HBV-infected liver. Direct ex vivo examination of virus-specific CD8 T cells binding HLA-A2/peptide multimers revealed that Tim-3 was more highly upregulated on HBV-specific CD8 T cells than CMV-specific CD8 T cells or the global CD8 T cell population in patients with CHB (p<0.001) or than on HBV-specific CD8 after resolution of infection. T cells expressing Tim-3 had an impaired ability to produce IFN-γ and TNF-α upon recognition of HBV-peptides and were susceptible to galectin-9-triggered cell death in vitro. Galectin-9 was detectable at increased concentrations in the sera of patients with active CHB-related liver inflammation (p = 0.02) and was strongly expressed by Kupffer cells within the liver sinusoidal network. Tim-3 blockade resulted in enhanced expansion of HBV-specific CD8 T cells able to produce cytokines and mediate cytotoxicity in vitro. Blocking PD-1 in combination with Tim-3 enhanced the number of patients from whom functional antiviral responses could be recovered and/or the strength of responses, indicating that these co-inhibitory molecules play a non-redundant role in driving T cell exhaustion in CHB. Patients taking antivirals able to potently suppress HBV viraemia continued to express Tim-3 on their T cells and respond to Tim-3 blockade. In summary, both Tim-3 and galectin-9 are increased in CHB and may contribute to the inhibition and deletion of T cells as they infiltrate the HBV-infected liver.     

Decreased Galectin-9 and Increased Tim-3 Expression Are Related to Poor Prognosis in Gastric Cancer

Introduction

Galectin-9 (Gal-9) induces adhesion and aggregation of certain cell types and inhibits the metastasis of tumor cells. T-cell immunoglobulin–and mucin domain-3–containing molecule 3 (TIM-3) plays a pivotal role in immune regulation. The aim of this study is to investigate Gal-9 and TIM-3 alterations in gastric cancer and their prognostic values.

Methods

Gal-9 and Tim-3 expression was evaluated using a tissue microarray immunohistochemistry method in 305 gastric cancers, of which 84 had paired adjacent normal samples. Cell lines SGC-7901, BGC-823, MGC-803, MKN45 and GES-1 were also stained. Correlations were analyzed between expression levels of Gal-9 and Tim-3 protein and tumor parameters or clinical outcomes.

Results

Gal-9 and Tim-3 stained positive on tumor cells in 86.2% (263/305), and 60.0% (183/305) patients with gastric cancer, respectively. Gal-9 expression was significantly higher in cancer than in normal mucosa (P<0.001). Reduced Gal-9 expression was associated with lymph-vascular invasion, lymph node metastasis, distant metastasis and worse TNM staging (P = 0.034, P = 0.009, P = 0.002 and P = 0.043, respectively). In contrast, Tim-3 expression was significantly lower in cancer than in control mucosa (P<0.001). Patients with lymph-vascular invasion had higher expression levels of Tim-3 (P<0.001). Moreover, multivariate analysis shows that both high Gal-9 expression and low Tim-3 expression were significantly associated with long overall survival (P = 0.002, P = 0.010, respectively); the combination of Gal-9 and Tim-3 expression was an independent prognostic predictor for patients with gastric cancer (RR: 0.43; 95%CI: 0.20–0.93). H.pylori infection status was not associated with Gal-9 and Tim-3 expression (P = 0.102, P = 0.565).

Conclusion

The results suggest that expression of Gal-9 and Tim-3 in tumor cells may be a potential, independent prognostic factor for patients with gastric cancer. Gal-9 and TIM-3 may play an important part in the gastric carcinogenesis.     

JunD regulates lymphocyte proliferation and T helper cell cytokine expression

Transgenic mice broadly expressing JunD (Ubi-junD(m)) appear phenotypically normal, but have strongly reduced numbers of peripheral lymphocytes. JunD overexpression in lymphocytes does not protect from numerous apoptotic insults; however, transgenic T cells proliferate poorly and exhibit impaired activation due to reduced levels of IL-4, CD25 and CD69. Consistently, in the absence of JunD (junD(-/-)) T cells hyperproliferate following mitogen induction. Moreover, transgenic T helper (Th) 2 cells have decreased IL-4 and IL-10 expression, whereas junD(-/-) Th2 cells secrete higher amounts of both Th2 cytokines. Th1-polarized junD(-/-) CD4(+) T cells display enhanced IFN-gamma cytokine production associated with upregulated T-bet expression and downregulated expression of suppressor of cytokine signaling-1. These novel findings demonstrate a regulatory role of JunD in T lymphocyte proliferation and Th cell differentiation.     

Increased expression of Tim-3 and its ligand Galectin-9 in rat allografts during acute rejection episodes

The aim of the study is to elucidate the profiles of T-cell immunoglobulin and mucin domain-3 (Tim-3) and its ligand Galecin-9 in acute pulmonary rejection by using a rat model of lung transplantation. Left lung grafts retrieved from Lewis or Fisher 344 rats were orthotopically transplanted into Lewis recipients without any immunosuppressions; the grafts were harvested at day 3, 7 or 10 after transplantation. The grade of acute rejection was histopathologically evaluated. Tim-3, Galectin-9, immune antigen and related cytokines expression were assessed with immunological techniques and real-time polymerase chain reaction (RT-PCR), respectively. Then, our results showed that Tim-3 and its ligand Galectin-9 were markedly up-regulated at protein and mRNA levels in allografts compared with syngrafts. Meanwhile, the decreased CD4/CD8 ratio was associated with acute rejection occurring and Tim-3 expression on CD4⁺ and CD8⁺ T cells in allografts was increased. Therefore, our study firstly described that enhanced Tim-3 and its ligand Galectin-9 in allografts might play an important role in the pathogenesis of rat lung transplant rejection, implying new valuable markers for detecting acute allograft rejection.     

Galectin-9 controls CD40 signaling through a Tim-3 independent mechanism and redirects the cytokine profile of pathogenic T cells in autoimmunity

While it has long been understood that CD40 plays a critical role in the etiology of autoimmunity, glycobiology is emerging as an important contributor. CD40 signaling is also gaining further interest in transplantation and cancer therapies. Work on CD40 signaling has focused on signaling outcomes and blocking of its ligand, CD154, while little is known about the actual receptor itself and its control. We demonstrated that CD40 is in fact several receptors occurring as constellations of differentially glycosylated forms of the protein that can sometimes form hybrid receptors with other proteins. An enticing area of autoimmunity is differential glycosylation of immune molecules leading to altered signaling. Galectins interact with carbohydrates on proteins to effect such signaling alterations. Studying autoimmune prone NOD and non-autoimmune BALB/c mice, here we reveal that in-vivo CD40 signals alter the glycosylation status of non-autoimmune derived CD4 T cells to resemble that of autoimmune derived CD4 T cells. Galectin-9 interacts with CD40 and, at higher concentrations, prevents CD40 induced proliferative responses of CD4(lo)CD40(+) effector T cells and induces cell death through a Tim-3 independent mechanism. Interestingly, galectin-9, at lower concentrations, alters the surface expression of CD3, CD4, and TCR, regulating access to those molecules and thereby redirects the inflammatory cytokine phenotype and CD3 induced proliferation of autoimmune CD4(lo)CD40(+) T cells. Understanding the dynamics of the CD40 receptor(s) and the impact of glycosylation status in immunity will gain insight into how to maintain useful CD40 signals while shutting down detrimental ones.     

Defective thymic education of L3T4+ T helper cell function in graft-vs-host mice

Our study investigates the effect of a prior graft-vs-host (GVH) reaction on the subsequent ability of irradiated, bone marrow-re-populated mice to develop T cell function. The results indicate that such GVH-bone marrow transplanted (BMT) mice do not generate CTL responses to trinitrophenyl-modified syngeneic cells (TNP-self), but do generate strong CTL activity to H-2 alloantigens. This selective deficiency in TNP-self CTL response potential appeared as early as 10 days after GVH, and required both L3T4+ and Lyt-2+ donor T cells. The in vitro addition of either soluble Th factors or L3T4-enriched spleen cells from normal mice circumvented the defect in the TNP-self response in GVH-BMT mice. These results indicate that T effector function was not defective, and instead suggest a Th defect. Cell depletion and antibody-blocking, as well as IL-2 production experiments, indicate that the Th defect was selective for L3T4+ Th population and not for Lyt-2+ Th population. This defect in L3T4 Th function is not accounted for by the approximate twofold reduction in L3T4 cell numbers in GVH-BMT mice, because IL-2 production and CTL generation to L3T4-dependent Ag were at least eightfold below control levels. Rather, defective L3T4 Th function appears to be the consequence of a GVH-induced defect in thymic maturation because the defect was corrected in vivo by a neonatal parental thymus graft before irradiation and bone marrow transplantation. This system may be useful for elucidating the role of the thymus in the maturation of Th cells. Our findings raise the possibility that impaired development of T cell function occurring in marrow grafted patients who have undergone a GVH reaction could be partly due to a GVH-induced thymic defect.     

Propagation of antigen-specific T cell helper function in vitro.

Antigen-induced proliferation of primed lymph node cells was abrogated by treatment with anti-Ly 1 serum and complement (C) but not with anti-Ly 2 serum and C. Lymph node cells from animals primed to ovalbumin were activated with antigen in vitro, followed by propagation in an antigen-free supernatant fluid obtained from lectin-induced normal spleen cells. T cells processed in this manner displayed a stepwise enrichment of helper activity for antibody production as measured in a secondary hapten-carrier response. The sequential increase in antigen-specific help was paralleled by a rise in the antigen-induced proliferative response, a phenomenon whose expression was dependent on the presence of syngeneic or semi-syngeneic irradiated filler cells.     

Tim-3 negatively regulates cytotoxicity in exhausted CD8+ T cells in HIV infection

Cytotoxic CD8(+) T cells (CTLs) contain virus infections through the release of granules containing both perforin and granzymes. T cell 'exhaustion' is a hallmark of chronic persistent viral infections including HIV. The inhibitory regulatory molecule, T cell Immunoglobulin and Mucin domain containing 3 (Tim-3) is induced on HIV-specific T cells in chronic progressive infection. These Tim-3 expressing T cells are dysfunctional in terms of their capacities to proliferate or to produce cytokines. In this study, we evaluated the effect of Tim-3 expression on the cytotoxic capabilities of CD8(+) T cells in the context of HIV infection. We investigated the cytotoxic capacity of Tim-3 expressing T cells by examining 1) the ability of Tim-3(+) CD8(+) T cells to make perforin and 2) the direct ability of Tim-3(+) CD8(+) T cells to kill autologous HIV infected CD4(+) target cells. Surprisingly, Tim-3(+) CD8(+) T cells maintain higher levels of perforin, which was mainly in a granule-associated (stored) conformation, as well as express high levels of T-bet. However, these cells were also defective in their ability to degranulate. Blocking the Tim-3 signalling pathway enhanced the cytotoxic capabilities of HIV specific CD8(+) T cells from chronic progressors by increasing; a) their degranulation capacity, b) their ability to release perforin, c) their ability to target activated granzyme B to HIV antigen expressing CD4(+) T cells and d) their ability to suppress HIV infection of CD4(+) T cells. In this latter effect, blocking the Tim-3 pathway enhances the cytotoxcity of CD8(+) T cells from chronic progressors to the level very close to that of T cells from viral controllers. Thus, the Tim-3 receptor, in addition to acting as a terminator for cytokine producing and proliferative functions of CTLs, can also down-regulate the CD8(+) T cell cytotoxic function through inhibition of degranulation and perforin and granzyme secretion.     

Galectin-9 Ameliorates Clinical Severity of MRL/lpr Lupus-Prone Mice by Inducing Plasma Cell Apoptosis Independently of Tim-3

Galectin-9 ameliorates various murine autoimmune disease models by regulating T cells and macrophages, although it is not known what role it may have in B cells. The present experiment shows that galectin-9 ameliorates a variety of clinical symptoms, such as proteinuria, arthritis, and hematocrit in MRL/lpr lupus-prone mice. As previously reported, galectin-9 reduces the frequency of Th1, Th17, and activated CD8⁺ T cells. Although anti-dsDNA antibody was increased in MRL/lpr lupus-prone mice, galectin-9 suppressed anti-dsDNA antibody production, at least partly, by decreasing the number of plasma cells. Galectin-9 seemed to decrease the number of plasma cells by inducing plasma cell apoptosis, and not by suppressing BAFF production. Although about 20% of CD19^−/low CD138⁺ plasma cells expressed Tim-3 in MRL/lpr lupus-prone mice, Tim-3 may not be directly involved in the galectin-9-induced apoptosis, because anti-Tim-3 blocking antibody did not block galectin-9-induced apoptosis. This is the first report of plasma cell apoptosis being induced by galectin-9. Collectively, it is likely that galectin-9 attenuates the clinical severity of MRL lupus-prone mice by regulating T cell function and inducing plasma cell apoptosis.     

Folate deficiency affects dendritic cell function and subsequent T helper cell differentiation

Insufficient folate status may be related to the increasing prevalence of immune- or inflammation-related chronic diseases. To investigate the effects of folate on immune regulation, we examined the impact of folate deficiency (FD) on dendritic cell (DC) maturation and function and, thus, T helper (Th) cells differentiation. First, bone marrow-derived DCs (BMDCs) were generated from BALB/c mice bone marrow cells cultured in folate-containing (F-BMDCs) or folate-deficient (FD-BMDCs) medium. FD-BMDC displayed more immature phenotype including reduced levels of major histocompatibility complex class II (MHC II), co-stimulatory molecules and characteristic of higher endocytic activity. FD-BMDC produced less IL-12p70 and proinflammatory cytokines in response to lipopolysaccharide. This aberrant DC maturation due to FD resulted in reduced BMDC-induced Th cell activity and lower IL-2, IFNγ, IL-13 and IL-10 productions. Further in vivo study confirmed significantly lower IFNγ and IL-10 productions by T cells and showed higher splenic naïve Th and lower memory T, effector T and regulatory T cell (Treg) percentages in mice fed with the FD diet for 13 weeks. To investigate the role of DCs on T cell activity, splenic DCs (spDC) from FD mice were cocultured with Th cells. The FD spDC had lower MHC II and CD80 expressions and subsequently impaired DC-induced Th differentiation, shown as decreased cytokine productions. This study demonstrated that folate deficiency impaired DC functions and, thus, Th differentiation and responses, suggesting that folate plays a crucial role in maintaining Th cells homeostasis.     

A polyclonal assay for T helper function involving T-B cell contact mediated by L3T4 molecules

In the presence of pokeweed mitogen (PWM), T helper (TH) cell clones can induce differentiation of a very high proportion of normal B lymphocytes into plasmocytes. This property can be used to test TH cell function regardless of clonal specificity. We have investigated the role of L3T4 surface antigen in this new assay. Only TH cell clones expressing the L3T4 antigen have effector activity in this PWM-dependent helper assay; L3T4- TH cell variants are inactive. The involvement of L3T4 antigen is further shown by the ability of anti-L3T4 monoclonal antibody to inhibit the PWM-dependent polyclonal B cell differentiation induced by L3T4+ TH cell clones. This inhibition is not the consequence of arrested TH cell activation, nor of a lack of appropriate B cell stimulation by TH cell lymphokines. We show that PWM focuses TH cells on the B cell hybridoma LB15-13, and that anti-L3T4 mAb prevents the T-B cell clustering mediated by PWM. Thus, by a mechanism comparable with the one described for concanavalin A in the cytotoxicity assay, PWM acts by bridging TH cells and B cells; the T cell surface antigen L3T4 is involved in this process.     

X-linked inhibitor of apoptosis regulates T cell effector function

To understand how the balance between pro- and anti-apoptotic signals influences effector function in the immune system, we studied the X-linked inhibitor of apoptosis (XIAP), an endogenous regulator of cellular apoptosis. Real-time PCR showed increased XIAP expression in blood of mice with experimental autoimmune encephalomyelitis, correlating with disease severity. Daily administration (10 mg/kg/day i.p.) of a 19-mer antisense oligonucleotide specific for XIAP (ASO-XIAP) abolished disease-associated XIAP mRNA and protein expression, and given from day of onset, alleviated experimental autoimmune encephalomyelitis and prevented relapses. Prophylactic treatment also reduced XIAP expression and prevented disease. Random or 5-base mismatched ASO was not inhibitory, and ASO-XIAP did not affect T cell priming. In ASO-XIAP-treated animals, infiltrating cells and inflammatory foci were dramatically reduced within the CNS. Flow cytometry showed an 88-93% reduction in T cells. The proportion of TUNEL(+) apoptotic CD4(+) T cells in the CNS was increased from <1.6 to 26% in ASO-XIAP-treated mice, and the proportion of Annexin V-positive CD4(+) T cells in the CNS increased. Neurons and oligodendrocytes were not affected; neither did apoptosis increase in liver, where XIAP knockdown also occurred. ASO-XIAP increased susceptibility of T cells to activation-induced apoptosis in vitro. Our results identify XIAP as a critical controller of apoptotic susceptibility of effector T cell function.     

Activation of c-Kit in dendritic cells regulates T helper cell differentiation and allergic asthma

Dendritic cells (DCs) are integral to the differentiation of T helper cells into T helper type 1 T(H)1, T(H)2 and T(H)17 subsets. Interleukin-6 (IL-6) plays an important part in regulating these three arms of the immune response by limiting the T(H)1 response and promoting the T(H)2 and T(H)17 responses. In this study, we investigated pathways in DCs that promote IL-6 production. We show that the allergen house dust mite (HDM) or the mucosal adjuvant cholera toxin promotes cell surface expression of c-Kit and its ligand, stem cell factor (SCF), on DCs. This dual upregulation of c-Kit and SCF results in sustained signaling downstream of c-Kit, promoting IL-6 secretion. Intranasal administration of antigen into c-Kit-mutant mice or neutralization of IL-6 in cultures established from the lung-draining lymph nodes of immunized wild-type mice blunted the T(H)2 and T(H)17 responses. DCs lacking functional c-Kit or those unable to express membrane-bound SCF secreted lower amounts of IL-6 in response to HDM or cholera toxin. DCs expressing nonfunctional c-Kit were unable to induce a robust T(H)2 or T(H)17 response and elicited diminished allergic airway inflammation when adoptively transferred into mice. Expression of the Notch ligand Jagged-2, which has been associated with T(H)2 differentiation, was blunted in DCs from c-Kit-mutant mice. c-Kit upregulation was specifically induced by T(H)2- and T(H)17-skewing stimuli, as the T(H)1-inducing adjuvant, CpG oligodeoxynucleotide, did not promote either c-Kit or Jagged-2 expression. DCs generated from mice expressing a catalytically inactive form of the p110delta subunit of phosphatidylinositol-3 (PI3) kinase (p110(D910A)) secreted lower amounts of IL-6 upon stimulation with cholera toxin. Collectively, these results highlight the importance of the c-Kit-PI3 kinase-IL-6 signaling axis in DCs in regulating T cell responses.     

Tim-3 Is Upregulated in NK Cells during Early Pregnancy and Inhibits NK Cytotoxicity toward Trophoblast in Galectin-9 Dependent Pathway

NK cells accumulate at the maternal-fetal interface (MFI) and play essential roles in maintaining immune tolerance during pregnancy. The mechanisms that facilitate NK cells tolerance to fetal tissue are largely unknown. T cell Ig and mucin domain-containing protein 3 (Tim-3) is a newly defined molecule with essential immunological function in many physiological and pathological processes. Recent study showed that Tim-3 was involved in the regulation of immune tolerance at MFI. However, whether Tim-3 regulates NK cells cytotoxicity toward trophoblasts is unclear. Here, we showed Tim-3 was mainly expressed by decidual NK cells (dNK) and Tim-3 level in dNK was higher than peripheral NK cells (pNK). Tim-3⁺ dNK expressed more levels of mature markers CD94 and CD69 than Tim-3^- dNK cells and blocking Tim-3 significantly inhibited dNK IFN-γ and TNF-α secretion. Furthermore, we found TGF-β1 may contribute to such up-regulation of Tim-3 in NK cells. Interestingly, blocking Tim-3 enhanced NK cytotoxicity toward trophoblast cell line HTR-8 but not K562. We found HTR-8 expressed Tim-3 ligand Galectin-9, in contrast K562 did not. Small interfering RNA-mediated silencing of Galectin-9 expression enhanced NK cytotoxicity toward HTR-8. We further showed Tim-3/Galecin-9 inhibited NK cytotoxicity toward trophoblast partially via impairing the degranulation process. In addition, clinical data showed that abnormal Tim-3 level on pNK might be associated with recurrent spontaneous abortion (RSA). Thus, our data demonstrate Tim-3/Galectin-9 pathway maintains local tolerance by suppressing NK cytotoxicity toward trophoblasts which may represent a new immunologic tolerance mechanism at MFI.