Activation of Tim-3-Galectin-9 pathway improves survival of fully allogeneic skin grafts

Unravelling the potential of TIM-3 gene polymorphism in allogeneic hematopoietic stem cell transplantation - a preliminary study

BACKGROUND

T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) molecule is a key regulator of the immune response by exerting an inhibitory effect on various types of immune cells. Understanding the role of TIM-3 in hematopoietic stem cell transplantation (HSCT) may improve transplant outcomes. Our study evaluated the potential association between TIM-3 polymorphisms, namely rs1036199 (A > C) or rs10515746 (C > A), changes which are located in exon 3 and the promoter region of the TIM-3 gene, and post-HSCT outcomes.

METHODS

One-hundred and twenty allogeneic HSCT patients and their respective donors were enrolled and genotyped for TIM-3 single nucleotide polymorphisms (SNPs) using real-time PCR with TaqMan assays.

RESULTS

We found that the presence of the rare alleles and heterozygous genotypes of studied SNP in recipients tended to protect against or increase the risk for acute graft-versus-host disease (aGvHD). For the rs1036199 polymorphism, recipients with the AC heterozygous genotype (p = 0.0287) or carrying the rarer C allele (p = 0.0334) showed a lower frequency of aGvHD development along all I-IV grades. A similar association was detected for the rs10515746 polymorphism as recipients with the CA genotype (p = 0.0095) or the recessive A allele (p = 0.0117) less frequently developed aGvHD. Furthermore, the rarer A allele of rs10515746 SNP was also associated with a prolonged aGvHD-free survival (p = 0.0424). Cytomegalovirus (CMV) infection was more common in patients transplanted with TIM-3 rs10515746 mismatched donors (p = 0.0229) and this association was also found to be independent of HLA incompatibility and pre-transplant CMV-IgG status. Multivariate analyses confirmed the role of these recessive alleles and donor-recipient TIM-3 incompatibility as an independent factor in aGvHD and CMV development.

CONCLUSIONS

Polymorphism of TIM-3 molecule may affect the immune response in HSCT patients. The recessive alleles of rs1036199 and rs10515746 SNPs decreased the risk of developing aGvHD. TIM-3 donor-recipient genetic matching may also affect the risk of post-transplant CMV infection, indicating the potential value of genetic profiling in optimizing transplant strategies.

Galectin-9 alleviates acute graft-versus-host disease after haplo-hematopoietic stem cell transplantation by regulating regulatory T cell/effector T cell imbalance

BACKGROUND

Acute graft-versus-host disease (aGVHD) arises from the imbalance of host T cells. Galectin-9 negatively regulates CD4 effector T cell (Th1 and Th17) function by binding to Tim-3. However, the relationship between Galectin-9/Tim-3 and CD4+ T subsets in patients with aGVHD after Haplo-HSCT (haploidentical peripheral blood hematopoietic stem cell transplantation) has not been fully elucidated. Here, we investigated the role of Galectin-9 and CD4+ T subsets in aGVHD after haplo-HSCT.

METHODS

Forty-two patients underwent Haplo-HSCT (26 without aGVHD and 16 with aGVHD), and 20 healthy controls were included. The concentrations of Galectin-9, interferon-gamma (IFN-γ), interleukin (IL)-4, transforming growth factor (TGF)-β, and IL-17 in the serum and culture supernatant were measured using enzyme-linked immunosorbent assay or cytometric bead array. The expression levels of Galectin-9, PI3K, p-PI3K, and p-mTOR protein were detected by western blot analysis. Flow cytometry was used to analyze the proportions of CD4+ T cell subsets. Bioinformatics analysis was performed.

RESULTS

In patients with aGVHD, regulatory T (Treg) cells and Galectin-9 decreased, and the Th1, Th17, and Treg cells were significantly imbalanced. Moreover, Treg and Galectin-9 were rapidly reconstituted in the early stage of patients without aGVHD after Haplo-HSCT, but Th17 cells were reconstituted slowly. Furthermore, Tim-3 upregulation on Th17 and Th1 cells was associated with excessive activation of the PI3K/AKT pathway in patients with aGVHD. Specifically, in vitro treatment with Galectin-9 reduced IFN-γ and IL-17 production while augmenting TGF-β secretion. Bioinformatics analysis suggested the potential involvement of the PI3K/AKT/mTOR pathway in aGVHD. Mechanistically, exogenous Galectin-9 was found to mitigate aGVHD by restoring the Treg/Teffs (effector T cells) balance and suppressing PI3K.

CONCLUSION

Galectin-9 may ameliorate aGVHD after haplo-HSCT by modulating Treg/Teffs balance and regulating the PI3K/AKT/mTOR pathway. Targeting Galectin-9 may hold potential value for the treatment of aGVHD.

The level of Tim-3+CD8+ T cells can serve as a potential marker for evaluating the severity of acute graft-versus-host disease after haplo-PBSCT

Early and accurate diagnosis of acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation is crucial for the prognosis of patients. This study identified a potential biomarker for the severity of aGVHD after human leukocyte antigen (HLA)-haploidentical peripheral blood hematopoietic stem cell transplantation (haplo-PBSCT). We included 20 healthy subjects and 57 patients who underwent haplo-PBSCT. Of these patients, 22 developed aGVHD after haplo-PBSCT. The results showed that patients with aGVHD had significantly increased levels of Tim-3+/Perforin+/Granzyme B+CD8+ T cells, but significantly decreased Galectin-9. The differences in Galectin-9 and Tim-3+/Granzyme B+CD8+ T cells between grade I-II aGVHD and III-IV aGVHD were also significant. In vitro, the apoptosis of CD8+ T cells from aGVHD patients was significantly increased after Tim-3/Galectin-9 pathway activation, which decreased Granzyme B secretion. As revealed by univariate analysis, the level of Tim-3+CD8+ T cells was a risk factor for severe aGVHD. ROC analysis demonstrated that high levels of Tim-3+CD8+ T cells had a significant diagnostic value for severe aGVHD, with an area under the curve of 0.854 and cut-off value of 14.155%. In conclusion, the binding of Tim-3 with exogenous Galectin-9 can promote apoptosis of CD8+ T cells and affect the secretion of Granzyme B. Tim-3+CD8+ T cells have the potential to serve as immunological markers for assessing the severity of aGVHD after haplo-PBSCT and identifying patients at a higher risk for severe aGVHD.

T-cell exhaustion in immune-mediated inflammatory diseases: New implications for immunotherapy

Immune-mediated inflammatory diseases(IMIDs) are referred to as highly disabling chronic diseases affecting different organs and systems. Inappropriate or excessive immune responses with chronic inflammation are typical manifestations. Usually in patients with chronic infection and cancer, due to long-term exposure to persistent antigens and inflammation microenvironment, T-cells are continuously stimulated and gradually differentiate into an exhausted state. Exhausted T-cells gradually lose effector function and characteristics of memory T-cells. However, existing studies have found that exhausted T-cells are not only present in the infection and tumor environment, but also in autoimmunity, and are associated with better prognosis of IMIDs. This suggests new prospects for the application of this reversible process of T-cell exhaustion in the treatment of IMID. This review will focus on the research progress of T-cell exhaustion in several IMIDs and its potential application for diagnosis and treatment in IMIDs.

Tim-3/Galectin-9 signaling pathway is involved in the cytokine changes in mice with alveolar echinococcosis

BACKGROUND

Tim-3/Galectin-9 is involved in the immune escape of many pathogens. However, the role of Tim-3/Galectin-9 in persistent infection of Echinococcus multilocularis (Em), which is related to immune escape, is still unclear.

OBJECTIVE

To investigate the role of Tim-3/Galectin-9 and related cytokines in mice with persistent infection of Em.

METHODS

Em infection model was established by injecting the protoscoleces. Serum was collected at days 2, 8, 30, 60, 90, 180 and 270 after infection. Lymphocytes were isolated from liver tissue samples with Ficoll. Tim-3 + CD4 + T percentage was analyzed by flow cytometry. CD4 + T cells were isolated from liver tissues of Em infected mice and cultured in vitro. The mRNA levels of Tim-3, Galectin-9, IFN-γ and IL-4 were detected by qRT-PCR. Cytokine levels in serum and culture supernatant (IFN-γ and IL-4) were analyzed by cytometric bead array.

RESULTS

The expression of Tim-3 and Galectin-9 mRNA significantly increased after 30 days of infection, reached peak on day 90, and then decreased slightly on days 180-270. The expression of IFN-γ mRNA, increased on day 2 and 8 after infection, slightly decreased on days 30-60, and obvious decreased on days 90-270, but were still higher than those of the control group. The expression of IL-4 mRNA gradually increased along with the time of infection. In serum of Em infected mice, level of IFN-γ peaked at day 30 and then gradually decreased; whereas IL-4 level peaked at day 90 and then gradually decreased. In vitro experiment found that Tim-3/Galectin-9 directly caused the changes in the levels of IFN-γ and IL-4.

CONCLUSIONS

Tim-3/Galectin-9 signaling pathway may be involved in the development of persistent infection of Em by regulating the production of Th1 and Th2 cytokines.

CD39 pathway inhibits Th1 cell function in tuberculosis

The role of CD39 pathway in Th1 cell function in tuberculosis (TB) is rarely elucidated. The present study aims to investigate the modulating mechanism of CD39 pathway during Mycobacterium tuberculosis (MTB) infection. CD39 expression was examined on host immune cells among patients with TB. The relationship between CD39 expression and Th1 cell function was analysed. Patients with TB displayed dramatically higher CD39 expression on Th1 cells than healthy controls, and a significantly increased expression of surface markers, including activation, exhaustion and apoptosis markers, were noted in CD39⁺ Th1 cells in comparison with CD39⁻ Th1 cells. Conversely, CD39 expression on Th1 cells was associated with diminished number of polyfunctional cells producing Th1‐type cytokines, and CD39⁺ Th1 cells showed obviously lower proliferation potential. Notably, tetramer analysis demonstrated a predominant CD39 expression on TB‐specific CD4⁺ cells, which was associated with higher apoptosis and lower cytokine‐producing ability. Transcriptome sequencing identified 27 genes that were differentially expressed between CD39⁺ and CD39⁻ Th1 cells, such as IL32, DUSP4 and RGS1. Inhibition of CD39 pathway could enhance the activation, proliferation and cytokine‐producing ability of Th1 cells. Furthermore, there was a significantly negative correlation between CD39 expression on Th1 cells and nutritional status indicators such as lymphocyte count and albumin levels, and we observed a significant decline in CD39 expression on Th1 cells after anti‐TB treatment. CD39 is predominantly expressed on TB‐specific Th1 cells and correlated with their exhausted function, which suggests that CD39 could serve as a prominent target for TB therapy.

T-Cell Immunoglobulin and Mucin Domain 1 (TIM-1) Is a Functional Entry Factor for Tick-Borne Encephalitis Virus

Tick-borne encephalitis virus (TBEV) is the causative agent of a potentially fatal neurological infection affecting humans. The host factors required for viral entry have yet to be described. Here, we found that T-cell immunoglobulin and mucin domain 1 (TIM-1) acted as the cellular entry factor for TBEV. Using a virus overlay protein binding assay, TIM-1 was identified as a virion-interacting protein. Cells that were relatively resistant to TBEV infection became highly susceptible to infection when TIM-1 was ectopically expressed. TIM-1 knockout and viral RNA bypass assays showed that TIM-1 functioned in the entry phase of TBEV infection. TIM-1 mediated TBEV uptake and was cointernalized with virus particles into the cell. Antibodies for TIM-1, soluble TIM-1, or TIM-1 knockdown significantly inhibited TBEV infection in permissive cells. Furthermore, in TIM-1 knockout mice, TIM-1 deficiency markedly lowered viral burden and reduced mortality and morbidity, highlighting the functional relevance of TIM-1 in vivo. With TIM-1, we have identified a key host factor for TBEV entry and a potential target for antiviral intervention. IMPORTANCE TBEV is a tick-transmitted flavivirus that causes serious diseases in the human central nervous system in Eurasia. The host determinants required for viral entry remain poorly understood. Here, we found that TIM-1 is a cellular entry factor for TBEV. Antibodies directed at TIM-1 or soluble TIM-1 treatment decreased virus infection in cell cultures. TIM-1 was cointernalized with virus particles into cells. TIM-1 deficiency significantly lowered viral burden and attenuated pathogenesis in the murine TBEV infection model. The demonstration of TIM-1 as a cellular entry factor for TBEV will improve understanding of virus infection and provide a target for antiviral development.

Lactate secreted by PKM2 upregulation promotes Galectin-9-mediated immunosuppression via inhibiting NF-κB pathway in HNSCC

Pyruvate kinase M2 as a key rate-limiting enzyme in glycolysis, it plays a critical role in metabolic reprogramming and carcinogenesis. However, whether PKM2 can promote immunosuppressive microenvironment formation remains unknown in head and neck squamous cell carcinoma (HNSCC). PKM2 expression was detected using immunohistochemical staining. The biological functions of PKM2 were investigated in vitro and in vivo. Lactate production and the expression of Galectin-9, a critical immunosuppression molecule, were detected after PKM2 knockdown and overexpression in HNSCC cells. The mechanism of lactate regulating Galectin-9 expression through NF-κB signaling was explored in vitro. Overexpression of PKM2 correlates with poor prognosis in HNSCC patients. Silencing PKM2 markedly inhibits proliferation and metastasis capacity in vivo and in vitro, and vice versa. The glycolysis and glycolytic capacity are significantly decreased after PKM2 silencing. Lactate secretion induced by PKM2 significantly promotes migration and invasion capacity. Furthermore, a positive correlation between PKM2 and Galectin-9 expression is observed in HNSCC tissues. The induction of Galectin-9 expression by PKM2 can be affected by a lactate transporter inhibitor. Mechanically, lactate impeded the suppressive transcriptional complex formation of NF-κB and histone deacetylase 3 (HDAC3), which released the transcription of Galectin-9 mediated by NF-κB signaling. Our findings demonstrate that lactate produced by PKM2 upregulation promotes tumor progression and Galectin-9-mediated immunosuppression via NF-κB signaling inhibition in HNSCC, which bridges metabolism and immunosuppression. The novel PKM2-lactate-Galectin-9 axis might be a potential therapeutic target in HNSCC.

Recent Advances in Costimulatory Blockade to Induce Immune Tolerance in Liver Transplantation

Liver transplantation is an effective therapy for end-stage liver disease. However, most postoperative patients must take immunosuppressive drugs to prevent organ rejection. Interestingly, some transplant recipients have normal liver function and do not experience organ rejection after the withdrawal of immunosuppressive agents. This phenomenon, called immune tolerance, is the ultimate goal in clinical transplantation. Costimulatory molecules play important roles in T cell-mediated immune responses and the maintenance of T cell tolerance. Blocking costimulatory pathways can alter T cell responses and prolong graft survival. Better understanding of the roles of costimulatory molecules has facilitated the use of costimulatory blockade to effectively induce immune tolerance in animal transplantation models. In this article, we review the state of the art in costimulatory pathway blockade for the induction of immune tolerance in transplantation and its potential application prospects for liver transplantation.

Galectin-9 as a biomarker of disease severity

Galectin-9 (Gal-9) is a β-galactoside binding lectin known for its immunomodulatory role in various microbial infections. Gal-9 is expressed in all organ systems and localized in the nucleus, cell surface, cytoplasm and the extracellular matrix. It mediates host-pathogen interactions and regulates cell signalling via binding to its receptors. Gal-9 is involved in many physiological functions such as cell growth, differentiation, adhesion, communication and death. However, recent studies have emphasized on the elevated levels of Gal-9 in autoimmune disorders, viral infections, parasitic invasion, cancer, acute liver failure, atopic dermatitis, chronic kidney disease, type-2 diabetes, coronary artery disease, atherosclerosis and benign infertility-related gynecological disorders. In this paper we have reviewed the potential of Gal-9 as a reliable, sensitive and non-invasive biomarker of disease severity. Tracking changes in Gal-9 levels and its implementation as a biomarker in clinical practice will be an important tool to monitor disease activity and facilitate personalized treatment decisions.

Increased Galectin-9 expression, a prognostic biomarker of aGVHD, regulates the immune response through the Galectin-9 induced MDSC pathway after allogeneic hematopoietic stem cell transplantation

Galectin-9 (Gal-9) is a β-galactoside-binding soluble lectin family member that exerts its primary biological functions via specific glycoconjugate interactions. Gal-9 expression is closely related to tumor occurrence, development, metastasis and prognosis. In transplant immunology, a high level of Gal-9 expression has been shown to markedly reduce the severity of acute graft rejection and effectively prolong survival time in organ and bone marrow transplantation (BMT) models. The main mechanism of Gal-9-mediated immunoregulation involves the Tim-3/Gal-9 axis in T cells. However, myeloid-derived suppressor cell (MDSC) accumulation in transgenic mice with persistently high Gal-9 expression was observed in a model of lung inflammation, indicating that a potential immunosuppressive mechanism distinct from the Gal-9/Tim-3 axis might exist. In the present study, increased Gal-9 expression and MDSC frequencies before acute graft-versus-host disease (aGVHD) onset were observed in patients who developed aGVHD. Patients with higher Gal-9 expression (≥14.8417 ng/ml) exhibited reduced overall survival and increased cumulative incidences of GVHD at +100 day. We considered the elevated Gal-9 expression before aGVHD onset a secondary inflammatory response. This increase might be part of a negative feedback pathway corresponding to aGVHD pathogenesis. Additionally, a high Gal-9 concentration induced MDSC proliferation in vivo and in vitro. Gal-9-induced MDSCs (G9-MDSCs) suppressed T cell proliferation and activation. An infusion of G9-MDSCs into a graft contributed to the successful control of severe aGVHD and long-term survival in an allogeneic (allo)-BMT mouse model. Thus, we speculated that increased Gal-9 expression after allo-hematopoietic stem cell transplantation is a potential prognostic biomarker of aGVHD. The Gal-9-associated immunosuppressive effects on aGVHD development might occurr through G9-MDSCs and were independent of the Gal-9/Tim-3 axis.

TIM-3 blockade combined with bispecific antibody MT110 enhances the anti-tumor effect of γδ T cells

As ideal cells that can be used for adoptive cell therapy, γδ T cells are a group of homogeneous cells with high proliferative and tumor killing ability. However, γδ T cells are apt to apoptosis and show decreased cytotoxicity under persistent stimulation in vitro and cannot aggregate at tumor sites efficiently in vivo, both of which are two main obstacles to tumor adoptive immunotherapy. In this study, we found that the immune checkpoint T-cell immunoglobulin domain and mucin domain 3 (TIM-3) were up-regulated significantly on γδ T cells during their ex vivo expansion and this up-regulation contributed to the dysfunction of γδ T cells. Although the killing ability of γδ T cells against breast cancer cells which exhibited a high level of epithelial cell adhesion molecule (EpCAM) was enhanced, the level of TIM-3 on γδ T cells was also further up-regulated under the application of the bispecific antibody MT110 (anti-CD3 × anti-EpCAM) which can redirect T cells to target cells. Besides, these γδ T cells with up-regulated TIM-3 exhibited an increased susceptibility to apoptosis. By reinvigorating dysfunctional γδ T cells and promoting them to accumulate at tumor sites, the combined use of TIM-3 inhibitor and MT110 could further enhance the anti-tumor effect of the adoptively transfused γδ T cells. These results may have clinical implications for the design of new translational anti-tumor regimens aimed at combining checkpoint blockade and immune cell redirection.

Different Expression Pattern of TIM-3 and Galectin-9 Molecules by Peripheral and Peritoneal Lymphocytes in Women with and without Endometriosis

Endometriosis is a gynecological condition that is associated with chronic pelvic inflammation, pain, and infertility. Although substantial evidence supports that immunological alterations contribute to its pathogenesis and we previously posed a pivotal role of Galectin-9 (Gal-9) in this disorder, the involvement of the TIM-3/Gal-9 pathway in the development of endometriosis-associated immunological abnormalities is not yet known. In the present study, multicolor flow cytometry was used to compare the immunophenotype and cell surface expression of TIM-3 and Gal-9 molecules on peripheral blood (PB) and peritoneal fluid (PF) lymphocytes of women with and without endometriosis. We found an altered distribution of different lymphocyte subpopulations, a markedly decreased TIM-3 labeling on all T and NK subsets and a significantly increased Gal-9 positivity on peripheral CD4+ T and Treg cells of the affected cohort. Furthermore, a significantly increased TIM-3 expression on CD4+T-cells and elevated Gal-9 labeling on all T and NK subsets was also revealed in the PF of the examined patients. In conclusion, our results suggest a persistent activation and disturbed TIM-3/Gal-9-dependent regulatory function in endometriosis, which may be involved in the impaired immune surveillance mechanisms, promotes the survival of ectopic lesions, and aids the evolution of reproductive failures in endometriosis.

Costimulation Blockade in Transplantation

T cells play a pivotal role in orchestrating immune responses directed against a foreign (allogeneic) graft. For T cells to become fully activated, the T-cell receptor (TCR) must interact with the major histocompatibility complex (MHC) plus peptide complex on antigen-presenting cells (APCs), followed by a second "positive" costimulatory signal. In the absence of this second signal, T cells become anergic or undergo deletion. By blocking positive costimulatory signaling, T-cell allo-responses can be aborted, thus preventing graft rejection and promoting long-term allograft survival and possibly tolerance (Alegre ML, Najafian N, Curr Mol Med 6:843-857, 2006; Li XC, Rothstein DM, Sayegh MH, Immunol Rev 229:271-293, 2009). In addition, costimulatory molecules can provide negative "coinhibitory" signals that inhibit T-cell activation and terminate immune responses; strategies to promote these pathways can also lead to graft tolerance (Boenisch O, Sayegh MH, Najafian N, Curr Opin Organ Transplant 13:373-378, 2008). However, T-cell costimulation involves an incredibly complex array of interactions that may act simultaneously or at different times in the immune response and whose relative importance varies depending on the different T-cell subsets and activation status. In transplantation, the presence of foreign alloantigen incites not only destructive T effector cells but also protective regulatory T cells, the balance of which ultimately determines the fate of the allograft (Lechler RI, Garden OA, Turka LA, Nat Rev Immunol 3:147-158, 2003). Since the processes of alloantigen-specific rejection and regulation both require activation of T cells, costimulatory interactions may have opposing or synergistic roles depending on the cell being targeted. Such complexities present both challenges and opportunities in targeting T-cell costimulatory pathways for therapeutic purposes. In this chapter, we summarize our current knowledge of the various costimulatory pathways in transplantation and review the current state and challenges of harnessing these pathways to promote graft tolerance (summarized in Table 10.1).

Multiple doses of adipose tissue-derived mesenchymal stromal cells induce immunosuppression in experimental asthma

In experimental house dust mite (HDM)‐induced allergic asthma, therapeutic administration of a single dose of adipose tissue‐derived mesenchymal stromal cells (MSCs) ameliorates lung inflammation but is unable to reverse remodeling. We hypothesized that multiple doses of MSCs might exert better therapeutic effects by reducing lung inflammation and remodeling but might also result in immunosuppressive effects in experimental asthma. HDM was administered intranasally in C57BL/6 mice. After the last HDM challenge, mice received two or three doses of MSCs (10⁵ cells per day) or saline intravenously. An additional cohort of mice received dexamethasone as a positive control for immunosuppression. Two and three doses of MSCs reduced lung inflammation, levels of interleukin (IL)‐4, IL‐13, and eotaxin; total leukocyte, CD4⁺ T‐cell, and eosinophil counts in bronchoalveolar lavage fluid; and total leukocyte counts in bone marrow, spleen, and mediastinal lymph nodes. Two and three doses of MSCs also reduced collagen fiber content and transforming growth factor‐β levels in lung tissue; however, the three‐dose regimen was more effective, and reduced these parameters to control levels, while also decreasing α‐actin content in lung tissue. Two and three doses of MSCs improved lung mechanics. Dexamethasone, two and three doses of MSCs similarly increased galectin levels, but only the three‐dose regimen increased CD39 levels in the thymus. Dexamethasone and the three‐dose, but not the two‐dose regimen, also increased levels of programmed death receptor‐1 and IL‐10, while reducing CD4⁺CD8^low cell percentage in the thymus. In conclusion, multiple doses of MSCs reduced lung inflammation and remodeling while causing immunosuppression in HDM‐induced allergic asthma.

Expression of the Tim3-galectin-9 axis is altered in drug-induced maculopapular exanthema

BACKGROUND

Drug-induced maculopapular exanthemas (MPEs) are mediated by Th1 CD4⁺ T cells. One of the mechanisms of control of Th1 cells in homeostasis is the interaction between the checkpoint inhibitor Tim3 and its physiological ligand galectin-9 (Gal9). Disorders affecting this axis may be responsible for various autoimmune and immunological diseases. The aim of this study was to determinate the influence of the Tim3-Gal9 axis on the development of MPE induced by drugs.

METHODS

Frequencies of different cell subsets and the expression of Tim3 and Gal9 were measured in peripheral blood by flow cytometry and in skin biopsies by immunohistochemistry. Gal9 expression was assessed by RT-qPCR; its release was measured by multiplex assay. The effects of blocking or enhancing the Tim3-Gal9 axis on monocyte-derived dendritic cell (moDC) maturation and T-cell proliferation were determined by flow cytometry.

RESULTS

The expression of Tim3 was significantly reduced in peripheral blood Th1 cells and in the skin of MPE patients vs controls. Gal9 expression and release were significantly reduced in patient peripheral blood and moDCs, respectively. The addition of exogenous Gal9 significantly reduced Tim3⁺ Th1 proliferation, although Treg proliferation increased.

CONCLUSION

This study showed the involvement of the Tim3-Gal9 axis in MPE. The reduced expression of Tim3 in Th1 cells together with the impaired expression of Gal9 in PBMCs and DCs appears to have a role in the development of the disease. The potential of Gal9 to suppress Th1 and enhance Treg proliferation makes it a promising tool for treating these reactions.

Assessment of serum Tim-3 and Gal-9 levels in predicting the risk of infection after kidney transplantation

Infection remains a major cause of morbidity and mortality after kidney transplantation (KT). Reliable biomarkers to predict post-transplant infection are lacking. We investigated the predictive performance of pre- and post-transplant levels of T-cell immunoglobulin and mucin domain-3 (Tim-3) and Galectin-9 (Gal-9), two pleiotropic immunomodulatory molecules, in early identification of infection. Serum Tim-3 and Gal-9 were paired measured before and 30 days after transplantation (PTD 30) in 95 KT recipients (KTRs). The decline rates of Tim-3 and Gal-9 were calculated relative to pre-transplant levels. KTRs with infection history had significantly higher levels of PTD 30 Tim-3 and Gal-9, and slower decrease rates of Gal-9 compared to non-infected recipients, while no difference was observed between two groups regarding pre-transplant levels. The AUCs for predicting 1-year post-transplant infection were 0.653 and 0.711 for post-transplant Tim-3 and Gal-9, 0.664 and 0.670 for relative Tim-3 and Gal-9, respectively. After adjusting for potential confounders, PTD 30 Tim-3, Gal-9 and relative Gal-9 remained as independent risk factors for post-transplant infection. Our results suggested that PTD 30 Tim-3 and Gal-9 and relative decrease of Gal-9 were promising predictors for identifying KTRs with high risk of infection, while pre-transplant Tim-3 and Gal-9 showed no predictive power to infection.

Current understanding of the immunosuppressive properties of mesenchymal stromal cells

Several studies have demonstrated the anti-inflammatory potential of mesenchymal stromal cells (MSCs) isolated from bone marrow, adipose tissue, placenta, and other sources. Nevertheless, MSCs may also induce immunosuppression when administered systemically or directly to injured environments, as shown in different preclinical disease models. MSCs express certain receptors, including toll-like receptors and the aryl-hydrocarbon receptor, that are activated by the surrounding environment, thus leading to modulation of their immunosuppressive activity. Once MSCs are activated, they can affect a wide range of immune cells (e.g., neutrophils, monocytes/macrophages, dendritic cells, natural killer cells, T and B lymphocytes), a phenomenon that has been correlated to secretion of several mediators (e.g., indolamine 2,3-dioxygenase, galectins, prostaglandin E₂, nitric oxide, and damage- and pathogen-associated molecular patterns) and stimulation of certain signaling pathways (e.g., protein kinase R, signal transducer and activator of transcription-1, nuclear factor-κB). Additionally, MSC manipulation and culture conditions, as well as the number of passages, duration of cryopreservation, and O₂ content available, can significantly affect the immunosuppressive properties of MSCs. This review sheds light on current knowledge regarding the mechanisms by which MSCs exert immunosuppressive effects both in vitro and in vivo, focusing on the receptors expressed by MSCs, the correlation between soluble factors secreted by MSCs and their immunosuppressive effects, and interactions between MSCs and immune cells.

Characterization of the hypersensitive response-like cell death phenomenon induced by targeting antiviral lectin griffithsin to the secretory pathway

Griffithsin (GRFT) is an antiviral lectin, originally derived from a red alga, which is currently being investigated as a topical microbicide to prevent transmission of human immunodeficiency virus (HIV). Targeting GRFT to the apoplast for production in Nicotiana benthamiana resulted in necrotic symptoms associated with a hypersensitive response (HR)-like cell death, accompanied by H2 O2 generation and increased PR1 expression. Mannose-binding lectins surfactant protein D (SP-D), cyanovirin-N (CV-N) and human mannose-binding lectin (hMBL) also induce salicylic acid (SA)-dependent HR-like cell death in N. benthamiana, and this effect is mediated by the lectin's glycan binding activity. We found that secreted GRFT interacts with an endogenous glycoprotein, α-xylosidase (XYL1), which is involved in cell wall organization. The necrotic effect could be mitigated by overexpression of Arabidopsis XYL1, and by co-expression of SA-degrading enzyme NahG, providing strategies for enhancing expression of oligomannose-binding lectins in plants.

T cell exhaustion implications during transplantation

Exhaustion of lymphocyte function, particularly T cell exhaustion, due to prolonged exposure to a high load of foreign antigen is commonly seen during chronic viral infection as well as antitumor immune responses. This phenomenon has been associated with a determined molecular mechanism and phenotypic manifestations on the cell surface. In spite of investigation of exhaustion, mostly about CD8 responses toward viral infections, recent studies have reported that chronic exposure to antigen may develop exhaustion in CD4 + T cells, B cells, and NK cells. Little is known with respect to lymphocyte exhaustion during transplantation and its effect on aberrant anti-graft responses. Through a same mechanobiology observed during chronic exposure of foreign viral antigens, alloantigen persistence mediated by allograft could develop a favorable circumstance for exhaustion of T cells responding to allograft. However, to achieve better manipulation approaches of this event to reduce the complications during transplantation, we need to be armed with a bulk of knowledge with regard to quality and quantity of T cell exhaustion occurring in various allografts, the kinetics of exhaustion development, the impression of immunosuppressive agents on the exhaustion, and the influence of exhaustion on graft survival and immune tolerance.

Comparative analysis of decidual and peripheral immune cells and immune-checkpoint molecules during pregnancy in wild-type and PACAP-deficient mice

PROBLEM

PACAP is a neuropeptide having a major relevance in the nervous system and in several peripheral organs including those of the reproductive system. PACAP-deficient mice have several morphological, biochemical, behavioral defects, and show reduced fertility. Female reproductive functions such as fertility, mating behavior, maternal behaviors, and implantation alterations have been widely investigated, but no comparative immune analyses are available in pregnant wild-type (WT) and PACAP knockout (KO) mice.

METHODS OF STUDY

Therefore, we performed a detailed immunophenotyping of decidual and peripheral immune cells and investigated the expression of two immune-checkpoint molecules by immune cells together with immunohistochemistry detecting Galectin-9 in placental tissues. We investigated the percentage of numerous immune cell populations in the periphery and in the decidua of pregnant mice.

RESULTS

We demonstrated a significant increase in the frequency of decidual Gal-9+ Th cells obtained from PACAP KO mice compared to the decidua of WT mice. We could not determine statistical differences in TIM-3 and programmed cell death-1 expression by different immune cells in the decidua and in the periphery between WT and KO mice. In conclusion, we could not find any significant alteration either in the distribution or in the cytotoxicity of the investigated decidual immune cells which could elucidate any reproductive alterations in PACAP KO mice.

CONCLUSION

The only remarkable finding is the recruitment of Gal-9+ Th cells to the decidua promoting local immune homeostasis in PACAP KO mice, which nevertheless cannot explain the reduced fertility observed in these mice.

Soluble Tim-3 and Gal-9 are associated with renal allograft dysfunction in kidney transplant recipients: A cross-sectional study

BACKGROUND

T cell immunoglobulin mucin-3 (Tim-3) has been reported to participate in the regulation of immune response and the induction of allograft tolerance. However, the association between Tim-3 and renal allograft dysfunction is unclear. We studied the expression of cellular and soluble Tim-3 (sTim-3), soluble galectin-9 (sGal-9) and carcinoembryonic antigen-related cell adhesion molecule-1 (sCEACAM-1) in kidney transplantation recipients (KTRs) to explore their roles in allograft dysfunction.

METHODS

96 KTRs (53 with stable graft and 43 with graft dysfunction) and 30 healthy controls (HC) were enrolled. Among the KTRs, 55 used Tacrolimus (TAC) and 41 used Sirolimus (SRL). In the dysfunction group, 29 recipients have undergone graft biopsy and 14 were classified as biopsy-proven rejection (BPR). Cellular Tim-3 was determined by flow cytometry. sTim-3 was determined by ELISA. sGal-9 and sCEACAM-1 were determined by Bio-Plex® suspension array system.

RESULTS

KTRs with renal dysfunction showed significantly higher levels of sTim-3 and sGal-9 but similar levels of cellular Tim-3 and sCEACAM-1 compared with stable recipients. Correlation analysis revealed that estimated glomerular filtration rate (eGFR) was negatively associated with sTim-3 and sGal-9. Both BPR and non-BPR groups showed comparable levels of Tim-3, Gal-9 and CEACAM-1. Moreover, SRL group showed significantly higher levels of sCEACAM-1 than TAC and HC groups.

CONCLUSIONS

sTim-3 and sGal-9 were promising biomarkers for allograft dysfunction, but unable to differentiate allograft rejection from other causes of renal dysfunction in KTRs. Moreover, long-term administration of sirolimus would up-regulate sCEACAM-1 level, while exert similar regulatory effects on Tim-3 and Gal-9 compared to tacrolimus.

Regulation of M1‑type and M2‑type macrophage polarization in RAW264.7 cells by Galectin‑9

Generally considered as a potent pro‑inflammatory signal, β‑galactosidelectin suppresses T cell receptor activation, can both promote and inhibit integrin‑mediated adhesion and is required in nuclear pre‑mRNA splicing. Galectin‑9 (Gal‑9), a member of β‑galactoside lectin, is involved many processes of T cell‑mediated diseases (such as autoimmune diseases and asthma) and immunomodulation of macrophages. Macrophages are involved in the occurrence of inflammation, development and digestion and other stages. At different stages of the inflammatory response, macrophages exhibit different phenotypes, but mainly two subtypes, classically (M1) or alternatively (M2) polarization. The purpose of this work is to investigate the effect of overexpression or knockdown of Gal‑9 on the macrophage polarization. Macrophage polarization was detected by flow cytometric profiling of secreted cytokines and specific surface markers expression, including nitric oxide synthase 2 (NOS2) and mannose receptor 1 (CD206). Protein and mRNA expression levels of TNF‑α, TGF‑β, IL‑6, IL‑10, NF‑κB, signal transducer and activator of transcription (Stat)1 and Stat3 were determined by ELISA, western blot analysis or qRT‑PCR. Our results implied that differentiation of the mouse macrophage line RAW264.7 into M1‑type and M2‑type macrophages is followed by marked variations of Gal‑9 expression. Furthermore, its overexpression and secretion are tightly associated with M2‑type macrophages, whereas its downregulation promotes macrophages to polarize into M1‑type macrophages, which confirmed by elevated CD206 and NOS2, respectively. In response to the changes of Gal‑9 expression, cytokines, transcription factors and regulators, including TNF‑α, IL‑6, NF‑κB, Stat1, TGF‑β, IL‑10, and Stat3, were tightly regulated and significantly associated with classically and alternatively activated macrophages. Consistent with characteristics of M1‑type macrophages, the transcriptional or translational expression levels or activity of TNF‑α, IL‑6, Stat1 and NF‑κB were markedly increased with knockdown of Gal‑9 in macrophages. By contrast, the expression levels or activity of TGF‑β, IL‑10 and Stat3 were clearly elevated in macrophages with Gal‑9 overexpression, which is closely related with M2‑type macrophages. Specific expression and secretion patterns of cytokines, transcription factors and regulators in M1‑type and M2‑type macrophages contribute to better understanding the role of Gal‑9 in regulation in macrophages. This study provides a new insight that Gal‑9 may be a new immunomodulatory target for macrophages.

Tim-3 signaling in peripheral NK cells promotes maternal-fetal immune tolerance and alleviates pregnancy loss

Pregnancy loss occurs in about 15% of clinically recognized pregnancies, and defective maternal-fetal immune tolerance contributes to more than 50% of these events. We found that signaling by the type I membrane protein T cell immunoglobulin and mucin-containing protein 3 (Tim-3) in natural killer (NK) cells had an essential protective role during early pregnancy. Tim-3 on peripheral NK (pNK) cells was transiently increased in abundance during the first trimester of pregnancy, which depended on interleukin-4 (IL-4)-signal transducer and activator of transcription 6 (STAT6) and progesterone signaling. Tim-3⁺ pNK cells displayed immunosuppressive activities, including the production of anti-inflammatory cytokines and the induction of regulatory T cells (T_regs) in a transforming growth factor-β1 (TGF-β1)-dependent manner. Tim-3 on pNK cells was stimulated by its ligand galectin-9 (Gal-9), leading to signaling by the kinases c-Jun N-terminal kinase (JNK) and AKT. In recurrent miscarriage (RM) patients, Tim-3 abundance on pNK cells was reduced and the immunosuppressive activity of Tim-3⁺ pNK cells was impaired. Compared to Tim-3⁺ pNK cells from donors with normal pregnancies, RM patient Tim-3⁺ pNK cells exhibited changes in DNA accessibility in certain genetic loci, which were reversed by inhibiting accessible chromatin reader proteins. Furthermore, Tim-3⁺ pNK cells, but not Tim-3^- pNK cells, reduced fetal loss in abortion-prone and NK cell-deficient mice. Together, our findings reveal a critical role for Tim-3-Gal-9 signaling-mediated immunoregulation by pNK cells in maternal-fetal immune tolerance and suggest that Tim-3 abundance on pNK cells is a potential biomarker for RM diagnosis.

Mesenchymal stem cells and their immunosuppressive role in transplantation tolerance

Since they were first described, mesenchymal stem cells (MSCs) have been shown to have important effector mechanisms and the potential for use in cell therapy. A great deal of research has been focused on unveiling how MSCs contribute to anti-inflammatory responses, including describing several cell populations involved and identifying soluble and other effector molecules. In this review, we discuss some of the contemporary evidence for use of MSCs in the field of immune tolerance, with a special emphasis on transplantation. Although considerable effort has been devoted to understanding the biological function of MSCs, additional resources are required to clarify the mechanisms of their induction of immune tolerance, which will undoubtedly lead to improved clinical outcomes for MSC-based therapies.

Noninvasive detection of acute renal allograft rejection by measurement of soluble Tim-3 in urine

The purpose of the present study was to assess whether urinary soluble T-cell immunoglobulin and mucin domain-containing protein 3 (sTim-3) could be adopted as a novel non‑invasive biomarker for acute rejection (AR) following renal transplantation. A total of 156 patients were enrolled between January 2006 and December 2009, comprising 49 patients with biopsy‑proven AR, 58 patients with stable grafts and no abnormal histological findings (NO‑AR), 10 patients with subclinical rejection (SCR) in protocol biopsies, 10 patients with acute tubular necrosis (ATN) and 29 patients with chronic allograft nephropathy (CAN). Additionally, urine samples from 40 healthy individuals were also collected as controls. The urinary concentration of sTim‑3 was determined by ELISA in the 156 renal allograft recipients and 40 healthy controls. Compared with NO‑AR and healthy controls, patients with AR excreted urinary sTim‑3 at a significantly higher level (4,356±440.4, 95% CI: 3,473‑5,242 ng/mmol creatinine). Likewise, patients with ATN exhibited a significantly lower level of urinary sTim‑3 (2,060±217, 95% CI: 1,679‑2,680 ng/mmol creatinine) than patients with AR. The discriminatory value was measured by the area under the receiver operating characteristic curve (ROC), which had a value of 0.88 (95% CI: 0.809‑0.951), demonstrating that sTim‑3 was a suitable marker for the diagnosis of AR. At a cut-off point of 1,836 ng/mmol creatinine, the sensitivity was 89.8% and the specificity was 82.8% (P<0.001). Amongst the patients with AR, patients with steroid‑resistant acute rejection (n=31) had significantly higher urinary sTim‑3 concentrations than patients with steroid‑sensitive acute rejection (n=18; 5,548±613.5, 95%CI: 4,287‑6,809 ng/mmol creatinine vs. 2,653±391.7, 95% CI: 1,830‑3,476 ng/mmol creatinine; P=0.0002). No significant difference in urinary sTim‑3 was found between patients with AR and CAN (3,920±543.5, 95% CI: 3,473‑5,242 ng/mmol creatinine), and a significantly higher level of Tim‑3 was excreted by patients with CAN compared with patients with NO‑AR and healthy controls (P<0.001). The present study, therefore, suggests that urinary sTim‑3 may be used as a valuable non‑invasive biomarker for the detection of AR. In addition, urinary sTim‑3 levels were demonstrated to be associated with the response to anti‑rejection therapy. The results of the present study may provide support future research into the screening of novel immune suppressants.

Human galectin-9 on the porcine cells affects the cytotoxic activity of M1-differentiated THP-1 cells through inducing a shift in M2-differentiated THP-1 cells

BACKGROUND

In xenotransplantation, immune rejection by macrophages occurs rapidly and remains a major obstacle. Studies to control immune rejection in macrophages have been continuing to date. Recent studies have reported that human galectin-9 (hGal-9) can regulate the function of regulatory T cells (Treg), as well as cytotoxicity T cells (CTL) and natural killer cells (NK). Although the effect of hGal-9 on lymphocytes has been well studied, the relationship between hGal-9 and myeloid cells has been scarcely studied.

METHODS

To confirm the decreased cytotoxic activity effect by hGal-9 in M1-differentiated THP-1 cells, we established the hGal-9 expressing transgenic porcine cell line. hGal-9 siRNA was transfected to transgenic cells and recombinant hGal-9 (rhGal-9) was treated to co-culturing condition, and then, flow cytometry assay was conducted for analyzing the cytotoxic activity of M1-differentiated THP-1 cells. Related inflammatory cytokines (IL-1β, IL-10, TNF-α, IL-6, IL-12, IL-23, and TGF-β) and related enzymes (iNOS and Arginase 1) were analyzed by qPCR and Western blot assay. To identify the shift in M1/M2-differentiated THP-1 cells, expression levels of CCR7, CD163, iNOS, and Arginase 1 and population of M2 marker positive cells were analyzed.

RESULTS

The expression levels of pro-inflammatory cytokines in M1-differentiated THP-1 cells co-cultured with hGal-9-expressing porcine kidney epithelial cells were decreased, but not in co-cultured THP-1 cells. However, the expression levels of anti-inflammatory cytokines were also increased in co-cultured M1-differentiated THP-1 cells. The cytotoxicity effect of M1-differentiated THP-1 cells on transgenic cells was decreased while the expression levels of anti-inflammatory cytokines and M2 macrophages-related molecules were increased. M2 differentiation program was turned on while M1 program was turned down by enhancing the phosphorylation levels of Akt and PI3K and the expression level of PPAR-γ. Due to these changes, differentiation of M2 program was enhanced in cells co-cultured with hGal-9.

CONCLUSIONS

These data suggested that hGal-9 has a reduction in M1-differentiated THP-1 cell cytotoxic activity-related acute immune rejection in pig-to-human xenotransplantation in addition to its role in lymphoid lineage immune cell regulation.

Advances in targeting co-inhibitory and co-stimulatory pathways in transplantation settings: the Yin to the Yang of cancer immunotherapy

In the past decade, the power of harnessing T-cell co-signaling pathways has become increasingly understood to have significant clinical importance. In cancer immunotherapy, the field has concentrated on two related modalities: First, targeting cancer antigens through highly activated chimeric antigen T cells (CAR-Ts) and second, re-animating endogenous quiescent T cells through checkpoint blockade. In each of these strategies, the therapeutic goal is to re-ignite T-cell immunity, in order to eradicate tumors. In transplantation, there is also great interest in targeting T-cell co-signaling, but with the opposite goal: in this field, we seek the Yin to cancer immunotherapy's Yang, and focus on manipulating T-cell co-signaling to induce tolerance rather than activation. In this review, we discuss the major T-cell signaling pathways that are being investigated for tolerance induction, detailing preclinical studies and the path to the clinic for many of these molecules. These include blockade of co-stimulation pathways and agonism of coinhibitory pathways, in order to achieve the delicate state of balance that is transplant tolerance: a state which guarantees lifelong transplant acceptance without ongoing immunosuppression, and with preservation of protective immune responses. In the context of the clinical translation of immune tolerance strategies, we discuss the significant challenge that is embodied by the fact that targeted pathway modulators may have opposing effects on tolerance based on their impact on effector vs regulatory T-cell biology. Achieving this delicate balance holds the key to the major challenge of transplantation: lifelong control of alloreactivity while maintaining an otherwise intact immune system.

Prevention of allograft rejection in heart transplantation through concurrent gene silencing of TLR and Kinase signaling pathways

Toll-like receptors (TLRs) act as initiators and conductors responsible for both innate and adaptive immune responses in organ transplantation. The mammalian target of rapamycin (mTOR) is one of the most critical signaling kinases that affects broad aspects of cellular functions including metabolism, growth, and survival. Recipients (BALB/c) were treated with MyD88, TRIF and mTOR siRNA vectors, 3 and 7 days prior to heart transplantation and 7, 14 and 21 days after transplantation. After siRNA treatment, recipients received a fully MHC-mismatched C57BL/6 heart. Treatment with mTOR siRNA significantly prolonged allograft survival in heart transplantation. Moreover, the combination of mTOR siRNA with MyD88 and TRIF siRNA further extended the allograft survival; Flow cytometric analysis showed an upregulation of FoxP3 expression in spleen lymphocytes and a concurrent downregulation of CD40, CD86 expression, upregulation of PD-L1 expression in splenic dendritic cells in MyD88, TRIF and mTOR treated mice. There is significantly upregulated T cell exhaustion in T cells isolated from tolerant recipients. This study is the first demonstration of preventing immune rejection of allogeneic heart grafts through concurrent gene silencing of TLR and kinase signaling pathways, highlighting the therapeutic potential of siRNA in clinical transplantation.

Human Galectin-9 Is a Potent Mediator of HIV Transcription and Reactivation

Identifying host immune determinants governing HIV transcription, latency and infectivity in vivo is critical to developing an HIV cure. Based on our recent finding that the host factor p21 regulates HIV transcription during antiretroviral therapy (ART), and published data demonstrating that the human carbohydrate-binding immunomodulatory protein galectin-9 regulates p21, we hypothesized that galectin-9 modulates HIV transcription. We report that the administration of a recombinant, stable form of galectin-9 (rGal-9) potently reverses HIV latency in vitro in the J-Lat HIV latency model. Furthermore, rGal-9 reverses HIV latency ex vivo in primary CD4+ T cells from HIV-infected, ART-suppressed individuals (p = 0.002), more potently than vorinostat (p = 0.02). rGal-9 co-administration with the latency reversal agent "JQ1", a bromodomain inhibitor, exhibits synergistic activity (p<0.05). rGal-9 signals through N-linked oligosaccharides and O-linked hexasaccharides on the T cell surface, modulating the gene expression levels of key transcription initiation, promoter proximal-pausing, and chromatin remodeling factors that regulate HIV latency. Beyond latent viral reactivation, rGal-9 induces robust expression of the host antiviral deaminase APOBEC3G in vitro and ex vivo (FDR<0.006) and significantly reduces infectivity of progeny virus, decreasing the probability that the HIV reservoir will be replenished when latency is reversed therapeutically. Lastly, endogenous levels of soluble galectin-9 in the plasma of 72 HIV-infected ART-suppressed individuals were associated with levels of HIV RNA in CD4+ T cells (p<0.02) and with the quantity and binding avidity of circulating anti-HIV antibodies (p<0.009), suggesting a role of galectin-9 in regulating HIV transcription and viral production in vivo during therapy. Our data suggest that galectin-9 and the host glycosylation machinery should be explored as foundations for novel HIV cure strategies.

The protective function of galectin-9 in liver ischemia and reperfusion injury in mice

Galectin-9 (Gal-9) has gained attention as a multifaceted player in adaptive and innate immunity. To elucidate the role of Gal-9, we used a mouse model of partial liver ischemia/reperfusion injury (IRI) with wild type (WT) and Gal-9 knockout (KO) mice as well as a recombinant galectin-9 (reGal-9) protein. We found that the expression of Gal-9 was enhanced endogenously in the liver especially by hepatocytes and Kupffer cells during warm IRI for a mouse liver, which causes massive destruction of liver tissue. Gal-9 was released into the extracellular space in the liver and the highest levels in the plasma at 1 hour after reperfusion. The present study elucidates a novel role of Gal-9 signaling in mouse liver IRI, by using Gal-9-deficient mice and a stable form of reGal-9 protein. In the circumstance of Gal-9 absence, liver damage due to ischemia/reperfusion (IR) exacerbated the severity as compared with WT. On the other hand, exogenously administered reGal-9 significantly ameliorated hepatocellular damage. It decreased the local infiltration of the inflammatory cells such as T cells, neutrophils, and macrophages, and it reduced the expression of proinflammatory cytokines/chemokines; then, it strongly suppressed the apoptosis of the liver cells. Interestingly, severe liver damage due to IR in Gal-9 KO mice was improved by the administration of reGal-9. In conclusion, Gal-9 engagement ameliorated local inflammation and liver damage induced by IR, and the present study suggests a significant role of Gal-9 in the maintenance of hepatic homeostasis. In conclusion, targeting Gal-9 represents a novel approach to protect from inflammation such as liver IRI. Exogenous Gal-9 treatment will be a new therapeutic strategy against innate immunity-dominated liver tissue damage.

Comparison of galectin expression signatures in rejected and accepted murine corneal allografts

PURPOSE

Although members of the galectin family of carbohydrate-binding proteins are thought to play a role in the immune response and regulation of allograft survival, little is known about the galectin expression signature in failed corneal grafts. The aim of this study was to compare the galectin expression pattern in accepted and rejected murine corneal allografts.

METHODS

Using BALB/c mice as recipients and C57BL/6 mice as donors, a total of 57 transplants were successfully performed. One week after transplantation, the grafts were scored for opacity by slit-lamp microscopy. Opacity scores of 3+ or greater on postoperative week 4 were considered rejected. Grafted corneas were harvested on postoperative week 4, and their galectin expressions were analyzed by Western blot and immunofluorescence staining.

RESULTS

As determined by the Western blot analyses, galectins-1, 3, 7, 8 and 9 were expressed in normal corneas. Although in both accepted and rejected grafts, expression levels of the 5 lectins were upregulated compared with normal corneas, there were distinct differences in the expression levels of galectins-8 and 9 between accepted and rejected grafts, as both the Western blot and immunofluorescence staining revealed that galectin-8 is upregulated, whereas galectin-9 is downregulated in the rejected grafts compared with the accepted grafts.

CONCLUSIONS

Our findings that corneal allograft rejection is associated with increased galectin-8 expression and reduced galectin-9 expression, support the hypothesis that galectin-8 may reduce graft survival, whereas galectin-9 may promote graft survival. As a potential therapeutic intervention, inhibition of galectin-8 and/or treatment with exogenous galectin-9 may enhance corneal allograft survival rates.

T-cell exhaustion in allograft rejection and tolerance

PURPOSE OF REVIEW

The role of T-cell exhaustion in the failure of clearance of viral infections and tumors is well established. There are several ongoing trials to reverse T-cell exhaustion for treatment of chronic viral infections and tumors. The mechanisms leading to T-cell exhaustion and its role in transplantation, however, are only beginning to be appreciated and are the focus of the present review.

RECENT FINDINGS

Exhausted T cells exhibit a distinct molecular profile reflecting combinatorial mechanisms involving the interaction of multiple transcription factors important in control of cell metabolism, acquisition of effector function and memory capacity. Change of microenvironmental cues and limiting leukocyte recruitment can modulate T-cell exhaustion. Impaired leukocyte recruitment induces T-cell exhaustion and prevents allograft rejection.

SUMMARY

Preventing or reversing T-cell exhaustion may lead to prevention of transplant tolerance or triggering of rejection; therefore, caution should be exercised in the use of agents blocking inhibitory receptors for the treatment of chronic viral infections or tumors in transplant recipients. Further definition of the role of T-cell exhaustion in clinical transplantation and an understanding of the mechanisms of induction of T-cell exhaustion are needed to develop strategies for preventing allograft rejection and induction of tolerance.

Regulation of T cell responses by the receptor molecule Tim-3

Tim-3 is a member of the T cell immunoglobulin and mucin domain (Tim) family of proteins, which are expressed by several cell types in the immune system, including CD4 and CD8 T cells activated under certain conditions. These molecules are generally thought to act as receptors for multiple ligands and thus to function by engaging intracellular signaling pathways in a ligand-dependent manner. In recent years, the function of the Tim-3 protein has been studied in some detail, particularly with respect to its role in the regulation of CD4 and CD8 T cell responses. Here, we review the structural features of Tim-3, known ligands for this molecule and the links established between Tim-3 and signal transduction pathways. In addition, we review the current literature regarding the role of Tim-3 in the regulation of effector responses by CD4 and CD8 T cells. Overall, findings published thus far strongly support the conclusion that Tim-3 functions to inhibit T cell responses, particularly under conditions involving chronic stimulation. Conversely, some reports have provided evidence that Tim-3 can stimulate T cells under conditions involving acute stimulation, suggesting that the role of Tim-3 may vary depending on context. Further study of Tim-3 is likely to advance our understanding of how CD4 and CD8 T cell responses are regulated and could uncover novel approaches for manipulating T cell function for therapeutic benefit.

Tim-3 negatively mediates natural killer cell function in LPS-induced endotoxic shock

Sepsis is an exaggerated inflammatory condition response to different microorganisms with high mortality rates and extremely poor prognosis. Natural killer (NK) cells have been reported to be the major producers of IFN-γ and key players in promoting systematic inflammation in lipopolysaccharide (LPS)-induced endotoxic shock. T-cell immunoglobulin and mucin domain (Tim)-3 pathway has been demonstrated to play an important role in the process of sepsis, however, the effect of Tim-3 on NK cell function remains largely unknown. In this study, we observed a dynamic inverse correlation between Tim-3 expression and IFN-γ production in NK cells from LPS-induced septic mice. Blockade of the Tim-3 pathway could increase IFN-γ production and decrease apoptosis of NK cells in vitro, but had no effect on the expression of CD107a. Furthermore, NK cell cytotoxicity against K562 target cells was enhanced after blocking Tim-3 pathway. In conclusion, our results suggest that Tim-3 pathway plays an inhibitory role in NK cell function, which might be a potential target in modulating the excessive inflammatory response of LPS-induced endotoxic shock.

Costimulatory pathways in kidney transplantation: pathogenetic role, clinical significance and new therapeutic opportunities

Costimulatory pathways play a key role in immunity, providing the second signal required for a full activation of adaptive immune response. Different costimulatory families (CD28, TNF-related, adhesion and TIM molecules), characterized by structural and functional analogies, have been described. Costimulatory molecules modulate T cell activation, B cell function, Ig production, cytokine release and many other processes, including atherosclerosis. Patients suffering from renal diseases present significant alterations of the costimulatory pathways, which might make them particularly liable to infections. These alterations are further pronounced in patients undergoing kidney transplantation. In these patients, different costimulatory patterns have been related to distinct clinical features. The importance that costimulation has gained during the last years has led to development of several pharmacological approaches to modulate this critical step in the immune activation. Different drugs, mainly monoclonal antibodies targeting various costimulatory molecules (i.e. anti-CD80, CTLA-4 fusion proteins, anti-CD154, anti-CD40, etc.) were designed and tested in both experimental and clinical studies. The results of these studies highlighted some criticisms, but also some promising findings and now costimulatory blockade is considered a suitable strategy, with belatacept (a CTLA-4 fusion protein) being approved as the first costimulatory blocker for use in renal transplantation. In this review, we summarize the current knowledge on costimulatory pathways in the setting of kidney transplantation. We describe the principal costimulatory molecule families, their role and clinical significance in patients undergoing renal transplantation and the new therapeutic approaches that have been developed to modulate the costimulatory pathways.

Tim-3 signaling pathway as a novel negative mediator in lipopolysaccharide-induced endotoxic shock

Sepsis is a complex clinical condition caused by a dysregulated immune response to an infection. However, the mechanism by which our immune system controls this amplified inflammation is largely unknown. In this study, we investigated whether Tim-3 pathway could serve as a negative mediator in lipopolysaccharide (LPS)-induced endotoxic shock. Our results showed that Tim-3 was expressed on CD4(+) T cells, CD8(+) T cells, and NK cells, and was significantly increased in the peritoneal cavity of septic mice. Tim-3 acted as a marker of immune exhaustion and Tim-3-positive T cells and NK cells had a lower interferon (IFN)-γ production. Furthermore, blockade of Tim-3 pathway significantly accelerated mortality in septic mice, while activation of this pathway prolonged survival time. In vitro administration of Tim-3 blocking antibody restored the release of IFN-γ from splenocytes and decreased splenocyte apoptosis, and increased levels of IFN-γ and tumor necrosis factor (TNF)-α were also detected in septic mice at 24h post in vivo administration of the antibody. In contrast, activation of Tim-3 pathway prevented cell proliferation. Thus, Tim-3 signaling pathway acts as a novel negative mediator in LPS-induced endotoxic shock and could be a potential therapeutic target for the treatment of sepsis.

Direct cytocidal effect of galectin-9 localized on collagen matrices on human immune cell lines

BACKGROUND

There is a continuous demand for new immunosuppressive agents for organ transplantation. Galectin-9, a member of the galactoside-binding animal lectin family, has been shown to suppress pathogenic T-cell responses in autoimmune disease models and experimental allograft transplantation. In this study, an attempt has been made to develop new collagen matrices, which can cause local, contact-dependent immune suppression, using galectin-9 and collagen-binding galectin-9 fusion proteins as active ingredients.

METHODS

Galectin-9 and galectin-9 fusion proteins having collagen-binding domains (CBDs) derived from bacterial collagenases and a collagen-binding peptide (CBP) were tested for their ability to bind to collagen matrices, and to induce Jurkat cell death in solution and in the collagen-bound state.

RESULTS

Galectin-9-CBD fusion proteins exhibited collagen-binding activity comparable to or lower than that of the respective CBDs, while their cytocidal activity toward Jurkat cells in solution was 80~10% that of galectin-9. Galectin-9 itself exhibited oligosaccharide-dependent collagen-binding activity. The growth of Jurkat cells cultured on collagen membranes treated with galectin-9 was inhibited by~90%. The effect was dependent on direct cell-to-membrane contact. Galectin-9-CBD/CBP fusion proteins bound to collagen membranes via CBD/CBP moieties showed a low or negligible effect on Jurkat cell growth.

CONCLUSIONS

Among the proteins tested, galectin-9 exhibited the highest cytocidal effect on Jurkat cells in the collagen-bound state. The effect was not due to galectin-9 released into the culture medium but was dependent on direct cell-to-membrane contact.

GENERAL SIGNIFICANCE

The study demonstrates the possible use of galectin-9-modified collagen matrices for local, contact-dependent immune suppression in transplantation.

Galectin-9 in combination with rapamycin induces cardiac allograft tolerance in mice

BACKGROUND

Galectin-9 serves opposing roles in the innate and adaptive immune systems. Galectin-9 triggers T-cell immunoglobulin mucin-3 (Tim-3) on T helper type 1 (Th1) cells, thereby terminating Th1 immunity and protecting allografts from host immune attacks. Meanwhile, galectin-9 promotes the maturation of dendritic cells (DCs) that deliver proinflammatory signals. We previously showed that galectin-9 significantly prolongs cardiac allograft survival in mice but failed to induce tolerance. This study aimed at improving the administration protocol to induce allograft tolerance. We examined whether rapamycin can reverse the proinflammatory effects of galectin-9 on DCs and whether rapamycin synergizes with galectin-9 to induce cardiac allograft tolerance.

METHODS

Monocytes/DCs from cardiac allografts were assessed for Tim-3 expression by flow cytometry. Costimulatory molecules CD80/CD86 were measured on galectin-9/rapamycin-treated bone marrow-derived DCs by flow cytometry. We performed heterotopic cervical cardiac transplantation using BALB/c donors and C57BL/6 recipients and assessed graft survival time. T cells of long-term surviving recipients were immunoassayed for interferon-γ and interleukin-4 secretion.

RESULTS

Allograft-infiltrating monocytes/DCs expressed high Tim-3 levels (47.3%±5.6%). Expression of CD80/CD86 was up-regulated on galectin-9-treated bone marrow-derived DCs, which was reversed by rapamycin. Combined treatment with galectin-9 and rapamycin promoted the permanent acceptance of fully mismatched grafts (survival time >180 days; n=6). However, treatment with galectin-9 or rapamycin alone was not sufficient to induce tolerance. Galectin-9/rapamycin-induced tolerance was associated with low donor-specific interferon-γ and interleukin-4 secretion.

CONCLUSIONS

Rapamycin inhibits proinflammatory effects of galectin-9 on DCs. Combined treatment of galectin-9 and rapamycin promotes allografts tolerance, which is associated with reduced Th1 and Th2 responses.

Involvement of Galectin-9/TIM-3 pathway in the systemic inflammatory response in early-onset preeclampsia

BACKGROUND

Preeclampsia is a common obstetrical disease affecting 3-5% of pregnancies and representing one of the leading causes of both maternal and fetal mortality. Maternal symptoms occur as an excessive systemic inflammatory reaction in response to the placental factors released by the oxidatively stressed and functional impaired placenta. The T-cell immunoglobulin domain and mucin domain (TIM) family is a relatively newly described group of molecules with a conserved structure and important immunological functions. Identification of Galectin-9 as a ligand for TIM-3 has established the Galectin-9/TIM-3 pathway as an important regulator of Th1 immunity and tolerance induction.

METHODS

The aim of our study was to investigate the expression and function of Galectin-9 and TIM-3 molecules by peripheral blood mononuclear cells and the possible role of Galectin-9/TIM-3 pathway in the immunoregulation of healthy pregnancy and early-onset preeclampsia. We determined TIM-3 and Gal-9 expression and cytotoxicicty of peripheral lymphocytes of early-onset preeclamptic women and healthy pregnant woman using flow cytometry.

RESULTS

Investigating peripheral lymphocytes of women with early-onset preeclampsia, our results showed a decreased TIM-3 expression by T cells, cytotoxic T cells, NK cells and CD56(dim) NK cells compared to healthy pregnant women. Interestingly, we found a notably increased frequency of Galectin-9 positive cells in each investigated lymphocyte population in the case of early-onset preeclamptic patients. We further demonstrated increased cytotoxic activity by cytotoxic T and CD56(dim) NK cells in women with early-onset preeclampsia. Our findings showed that the strongest cellular cytotoxic response of lymphocytes occurred in the TIM-3 positive subpopulations of different lymphocytes subsets in early-onset preeclampsia.

CONCLUSION

These data suggest that Gal-9/TIM-3 pathway could play an important role in the immune regulation during pregnancy and the altered Galectin-9 and TIM-3 expression could result an enhanced systemic inflammatory response including the activation of Th1 lymphocytes in preeclampsia.

Expression and function of galectins in the endometrium and at the human feto-maternal interface

Galectins are classified as lectins that share structural similarities and bind β-galactosides via a conserved carbohydrate recognition domain. So far 16 out of 19 identified galectins were shown to be present in humans and numerous studies revealed galectins as pivotal modulators of cell death, differentiation and growth. Galectins were highlighted to interact with both the adaptive and innate immune response. In the field of reproductive medicine and placenta research different roles for galectins have been proposed. Several galectins, being abundantly present at the human feto-maternal interphase and endometrium, were hypothesized to significantly contribute to endometrial receptivity and pregnancy physiology. Hence, this review outlines selected aspects of galectin action within endometrial function and at the feto-maternal interphase. Further current knowledge on galectins in reproductive and pregnancy disorders like endometriosis, abortion or preeclampsia is summarized.

Galectin-9 in tumor biology: a jack of multiple trades

Galectin family members have been shown to exert multiple roles in the context of tumor biology. Several recent findings support a similar multi-faceted role for galectin-9. Galectin-9 expression is frequently altered in cancer as compared to normal tissues. In addition, an increasing amount of evidence suggests that galectin-9 is involved in several aspects of tumor progression, including tumor cell adhesion and survival, immune escape and angiogenesis. Also, galectin-9 shows potential as a prognostic marker and a therapeutic target for several malignancies. In this review we summarize both the established and the emerging roles of galectin-9 in tumor biology and discuss the potential application of galectin-9 in anti-cancer therapy.

Rejection and regulation: a tight balance

PURPOSE OF REVIEW

Achieving allograft tolerance is the holy grail of transplantation. However, tolerance and rejection are two extreme ends of a scale that can be tipped in either direction. We review the novel effector and regulatory mechanisms involved and factors that tip the balance in favor of rejection or regulation.

RECENT FINDINGS

It is increasingly recognized that established T-cell phenotypes could change their commitments. New data point to the plasticity of Th17 cells in vivo with a reciprocal balance of Th17 cells and regulatory T cells (Tregs) driven by the local cytokine environment. Treg-cell profiles have been linked to acute and chronic allograft outcomes, and emerging data also indicate a novel role of a regulatory B-cell population. Current research efforts are looking into factors that tip the balance toward allograft tolerance by targeting cytokines, novel costimulatory pathways such as T-cell immunoglobulin mucin molecules, and components of innate immunity, particularly dendritic cells.

SUMMARY

The balance of effector and regulatory mechanisms contributing to allograft outcome is very complex. It is likely that targeting multiple pathways will be required to achieve tolerance. Further studies are warranted to define this balance and identify optimal combination of therapeutic interventions.

Profiling Lgals9 splice variant expression at the fetal-maternal interface: implications in normal and pathological human pregnancy

Disruption of fetal-maternal tolerance mechanisms can contribute to pregnancy complications, including spontaneous abortion. Galectin-9 (LGALS9), a tandem repeat lectin associated with immune modulation, is expressed in the endometrium during the mid and late secretory phases and in decidua during human early pregnancy. However, the role of LGALS9 during pregnancy remains poorly understood. We used real-time PCR and immunohistochemical staining to analyze the expression of Lgals9/LGALS9 during mouse gestation as well as in human tissues obtained from normal pregnancy and spontaneous abortions. In mice, three Lgals9 splice variants were detected, the expression of which was differentially regulated during gestation. Furthermore, decidual Lgals9 expression was deregulated in a mouse model of spontaneous abortion, whereas placental levels did not change. We further found that the LGALS9 D5 isoform suppresses interferon gamma production by decidual natural killer cells. In human patients, six Lgals9 splice variants were detected, and a decrease in Lgals9 D5/10 was associated with spontaneous abortion. Altogether, these results show a differential regulation of Lgals9 isoform expression during normal and pathological pregnancies and designate Lgals9 as a potential marker for adverse pregnancy outcomes.