Promotion of tissue inflammation by the immune receptor Tim-3 expressed on innate immune cells

Role of the blood-brain barrier in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system associated with demyelination and axonal loss eventually leading to neurodegeneration. MS exhibits many of the hallmarks of an inflammatory autoimmune disorder including breakdown of the blood-brain barrier (BBB). The BBB is a complex organization of cerebral endothelial cells, pericytes and their basal lamina, which are surrounded and supported by astrocytes and perivascular macrophages. In pathological conditions, lymphocytes activated in the periphery infiltrate the central nervous system to trigger a local immune response that ultimately damages myelin and axons. Cytotoxic factors including pro-inflammatory cytokines, proteases, and reactive oxygen and nitrogen species accumulate and may contribute to myelin destruction. Dysregulation of the BBB and transendothelial migration of activated leukocytes are among the earliest cerebrovascular abnormalities seen in MS brains and parallel the release of inflammatory cytokines. In this review we establish the importance of the role of the BBB in MS. Improvements in our understanding of molecular mechanism of BBB functioning in physiological and pathological conditions could lead to improvement in the quality of life of MS patients.

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.

Too much of a good thing? Tim-3 and TCR signaling in T cell exhaustion

T cell exhaustion is thought to be a natural mechanism for limiting immune pathology, although it may be desirable to circumvent this mechanism to help eliminate viral reservoirs or tumors. Although there are no definitive markers, a fingerprint for exhausted T cells has been described that includes the transmembrane proteins PD-1, LAG3, and Tim-3. However, apart from the recruitment of tyrosine phosphatases to PD-1, little is known about the biochemical mechanisms by which these proteins contribute to the development or maintenance of exhaustion. Tim-3 contains no known motifs for the recruitment of inhibitory phosphatases, but it may actually increase signaling downstream of TCR/CD3, at least under acute conditions. Other studies showed that T cell exhaustion results from chronic stimulation that extends the effector phase of T cell activation, at the expense of T cell memory. We suggest that Tim-3 may contribute to T cell exhaustion by enhancing TCR-signaling pathways.

The correlation of Tim-3 and IFN-γ expressions in mice infected with Toxoplasma gondii during gestation

The immunoinhibitory receptor T cell immunoglobulin domain and mucin domain-1 (Tim-1) and Tim-3 participate in the regulation of Th immune response as well as innate immunity. However, there is no report about the expression of Tim genes in Toxoplasma gondii-infected experimental models during pregnancy. In this study, Kunming outbred pregnant mice were infected with RH strain of T. gondii through vagina at days 10 to 16 of gestation, and the mRNA expressions of Tim-1, Tim-3, interleukin (IL)-4, and interferon (IFN)-γ in the placentas, uteri, and draining lumber aortic lymph nodes (LALNs) at day 18 of gestation were analyzed using quantitative real-time PCR (qRT-PCR). Compared with uninfected pregnant controls, significantly increased levels of IFN-γ and Tim-3 were detected in the placentas (P < 0.001), uteri (P = 0.003 and P = 0.017, respectively), and LALNs (P = 0.003 and P = 0.025, respectively) of T. gondii-infected mice; there were positive and significant correlations between Tim-3 and IFN-γ mRNA expression levels in the placentas (R(2) = 0.6331, P = 0.0011), uteri (R(2) = 0.5658, P = 0.003), and LALNs (R(2) = 0.5583, P = 0.0033) of infected mice. Tim-1 (P = 0.002) and IL-4 (P = 0.003) expressions were significantly increased in the placentas, but Tim-1 were significantly decreased in the uteri (P = 0.013) and LALNs (P < 0.001) of infected pregnant mice in comparison of uninfected pregnant controls. Our data suggested that Tim-3 may play a regulatory role in T. gondii-infected pregnant mouse model.

Phosphatidylserine receptors: enhancers of enveloped virus entry and infection

A variety of both RNA and DNA viruses envelop their capsids in a lipid bilayer. One of the more recently appreciated benefits this envelope is incorporation of phosphatidylserine (PtdSer). Surface exposure of PtdSer disguises viruses as apoptotic bodies; tricking cells into engulfing virions. This mechanism is termed apoptotic mimicry. Several PtdSer receptors have been identified to enhance virus entry and we have termed this group of proteins PtdSer-mediated virus entry enhancing receptors or PVEERs. These receptors enhance entry of a range of enveloped viruses. Internalization of virions by PVEERs provides a broad mechanism of entry with little investment by the virus itself. PVEERs may allow some viruses to attach to cells, thereby making viral glycoprotein/cellular receptor interactions more probable. Alternatively, other viruses may rely entirely on PVEERs for internalization into endosomes. This review provides an overview of PtdSer receptors that serve as PVEERs and the biology behind virion/PVEER interaction.

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Phosphatidylserine (PtdSer) receptors can mediate entry of enveloped viruses.

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PtdSer is present on the outer leaflet of the virion envelope.

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PtdSer receptors are expressed on a variety of primary cells and cell lines.

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Characteristics of PtdSer receptors that mediate virus entry are defined.

Immunoregulation of dendritic cells by the receptor T cell Ig and mucin protein-3 via Bruton's tyrosine kinase and c-Src

The receptor T cell Ig and mucin protein-3 (TIM-3) has emerged as an important regulator of innate immune responses. However, whether TIM-3-induced signaling promotes or inhibits the activation and maturation of dendritic cells (DCs) still remains uncertain. In addition, the TIM-3 signaling events involved in this immunoregulatory function are yet to be established. In this article, we report that TIM-3 crosslinking by anti-TIM-3 Ab inhibited DC activation and maturation by blocking the NF-κB pathway. After Ab-mediated crosslinking, TIM-3 became tyrosine phosphorylated, which then sequentially bound and activated the nonreceptor tyrosine kinases Bruton's tyrosine kinase (Btk) and c-Src. Activation of Btk-c-Src signaling in turn triggered the secretion of some inhibitory factor (or factors) from DCs that inhibited the NF-κB pathway and subsequent activation and maturation of DCs. Silencing of Btk or c-Src abrogated the inhibitory effects of TIM-3 on DCs. These results demonstrate an essential role for Btk-c-Src signaling in TIM-3-induced DC suppression. Thus, in addition to demonstrating an inhibitory role for TIM-3 signaling in DC activation, we define the molecular mechanism by which TIM-3 mediates this effect.

Astrocyte galectin-9 potentiates microglial TNF secretion

Background

Aberrant neuroinflammation is suspected to contribute to the pathogenesis of myriad neurological diseases. As such, determining the pathways that promote or inhibit glial activation is of interest. Activation of the surface glycoprotein T-cell immunoglobulin and mucin-domain containing protein 3 (Tim-3) by the lectin galectin-9 has been implicated in promoting innate immune cell activation by potentiating or synergizing toll-like receptor (TLR) signaling. In the present study we examined the role of the Tim-3/galectin-9 pathway in glial activation in vitro.

Method

Primary monocultures of microglia or astrocytes, co-cultures containing microglia and astrocytes, and mixed glial cultures consisting of microglia, astrocytes and oligodendrocytes were stimulated with poly(I:C) or LPS, and galectin-9 up-regulation was determined. The effect of endogenous galectin-9 production on microglial activation was examined using cultures from wild-type and Lgals9 null mice. The ability for recombinant galectin-9 to promote microglia activation was also assessed. Tim-3 expression on microglia and BV2 cells was examined by qPCR and flow cytometry and its necessity in transducing the galectin-9 signal was determined using a Tim-3 specific neutralizing antibody or recombinant soluble Tim-3.

Result

Astrocytes potentiated TNF production from microglia following TLR stimulation. Poly(I:C) stimulation increased galectin-9 expression in microglia and microglial-derived factors promoted galectin-9 up-regulation in astrocytes. Astrocyte-derived galectin-9 in turn enhanced microglial TNF production. Similarly, recombinant galectin-9 enhanced poly(I:C)-induced microglial TNF and IL-6 production. Inhibition of Tim-3 did not alter TNF production in mixed glial cultures stimulated with poly(I:C).

Conclusion

Galectin-9 functions as an astrocyte-microglia communication signal and promotes cytokine production from microglia in a Tim-3 independent manner. Activation of CNS galectin-9 likely modulates neuroinflammatory processes in which TNF and IL-6 contribute to either pathology or reparation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0144-0) contains supplementary material, which is available to authorized users.

Analysis of Tim-3 as a therapeutic target in prostate cancer

T cell immunoglobulin domain and mucin domain-containing molecule 3 (Tim-3) is a newly discovered immunomodulatory, which plays an important role in immunity regulation. Recent evidence suggests that Tim-3 is differentially regulated in a variety of tumors and has a potential as a therapeutic target. The aim of this study was to investigate the effect of Tim-3 on the development of prostate cancer (PCa). Tim-3 expressing on peripheral CD4+ T and CD8+ T cells was analyzed by flow cytometry. The relationships between Tim-3 expression and clinicopathological features were analyzed. Immunohistochemical expression of Tim-3 was examined in our large numbers of paraffin-fixed prostate tissues. Flow cytometry revealed that expression of Tim-3 was significantly increased on both CD4+ and CD8+ T cells in PCa patients than that in benign prostate hyperplasia (BPH) patients. Also, the level of Tim-3 on CD4+ T cells was positively correlated with CD8+ T cells in patients. Further analyses revealed that the levels of Tim-3 on CD4+ T cells and CD8+ T cells exhibited different expression patterns in terms of localization depending on pathological category of PCa and metastasis. Immunohistochemical analysis revealed that positive staining of Tim-3 in PCa but little or no staining of Tim-3 was observed in BPH epithelium. Tim-3 may affect the development and progression of PCa, which may provide knowledge for using Tim-3 as a novel therapy for effective PCa management.

A role for the TIM-3/GAL-9/BAT3 pathway in determining the clinical phenotype of multiple sclerosis

T-cell immunoglobulin and mucin domain 3 (Tim-3) ligates galectin-9 (Gal-9); this process, resulting in the inhibition of Th1 responses and in the apoptosis of antigen-specific cells, is hampered by binding of the molecular adaptor human leukocyte antigen B (HLA-B)-associated transcript 3 (Bat3) to the intracellular tail of Tim-3. Apoptosis of myelin basic protein (MBP)-specific T lymphocytes correlates with reduced rates of disease progression in multiple sclerosis (MS). We extensively analyzed the Tim-3/Gal-9/Bat3 pathway in 87 patients with a diagnosis of stable relapsing-remitting MS (RRMS), primary progressive MS (PPMS), or benign MS (BEMS), as well as in 40 healthy control (HC) subjects. Results showed that MBP-specific CD4(+)Tim-3(+), CD4(+)/Gal-9(+), and CD4(+)/Tim-3(+)/AV(+) (apoptotic) T lymphocytes were augmented in the BEMS group, whereas CD4(+)/Bat3(+) and CD8(+)/Bat3(+) T lymphocytes were increased and CD4(+)/Tim-3(+)/AV(+) T cells were reduced in the PPMS group (>2 fold and P<0.05 in all cases). Blocking the Tim-3/Gal-9 interaction with specific mAb reduced T-lymphocyte apoptosis and augmented production of IFNγ and IL-17 in the BEMS, RRMS, and HC groups, but not in the PPMS group. The Tim-3/Gal-9 interaction favors apoptosis of MBP-specific T lymphocytes in BEMS; this process is reduced in PPMS by the up-regulation of Bat3. Therapeutic interventions aimed at silencing Bat3 could be beneficial in MS.

Galectin-9-CD44 interaction enhances stability and function of adaptive regulatory T cells

The β-galactoside-binding protein galectin-9 is critical in regulating the immune response, but the mechanism by which it functions remains unclear. We have demonstrated that galectin-9 is highly expressed by induced regulatory T cells (iTreg) and was crucial for the generation and function of iTreg cells, but not natural regulatory T (nTreg) cells. Galectin-9 expression within iTreg cells was driven by the transcription factor Smad3, forming a feed-forward loop, which further promoted Foxp3 expression. Galectin-9 increased iTreg cell stability and function by directly binding to its receptor CD44, which formed a complex with transforming growth factor-β (TGF-β) receptor I (TGF-βRI), and activated Smad3. Galectin-9 signaling was further found to regulate iTreg cell induction by dominantly acting through the CNS1 region of the Foxp3 locus. Our data suggest that exogenous galectin-9, in addition to being an effector molecule for Treg cells, acts synergistically with TGF-β to enforce iTreg cell differentiation and maintenance.

Galectin-9 is rapidly released during acute HIV-1 infection and remains sustained at high levels despite viral suppression even in elite controllers

Galectin-9 (Gal-9) is a β-galactosidase-binding lectin that promotes apoptosis, tissue inflammation, and T cell immune exhaustion, and alters HIV infection in part through engagement with the T cell immunoglobulin mucin domain-3 (Tim-3) receptor and protein disulfide isomerases (PDI). Gal-9 was initially thought to be an eosinophil attractant, but is now known to mediate multiple complex signaling events that affect T cells in both an immunosuppressive and inflammatory manner. To understand the kinetics of circulating Gal-9 levels during HIV infection we measured Gal-9 in plasma during HIV acquisition, in subjects with chronic HIV infection with differing virus control, and in uninfected individuals. During acute HIV infection, circulating Gal-9 was detected as early as 5 days after quantifiable HIV RNA and tracked plasma levels of interleukin (IL)-10, tumor necrosis factor (TNF)-α, and IL-1β. In chronic HIV infection, Gal-9 levels positively correlated with plasma HIV RNA levels (r=0.29; p=0.023), and remained significantly elevated during suppressive antiretroviral therapy (median: 225.3 pg/ml) and in elite controllers (263.3 pg/ml) compared to age-matched HIV-uninfected controls (54 pg/ml). Our findings identify Gal-9 as a novel component of the first wave of the cytokine storm in acute HIV infection that is sustained at elevated levels in virally suppressed subjects and suggest that Gal-9:Tim-3 crosstalk remains active in elite controllers and antiretroviral (ARV)-suppressed subjects, potentially contributing to ongoing inflammation and persistent T cell dysfunction.

The role of T cell immunoglobulin and mucin domain-3 in immune thrombocytopenia

T cell immunoglobulin and mucin domain-3 (TIM-3), originally identified as a T helper (Th) 1-specific type I membrane protein, plays a vital role in Th1 immunity and tolerance induction through interaction with its ligand, galectin-9. The binding of TIM-3 by galectin-9 serves to downregulate Th1 responses. Moreover, the regulatory function of TIM-3 has been extended to other cells, such as Th17 cells, CD4(+) CD25(+) regulatory T cells (Tregs), CD8(+) T cells and certain innate immune cells. Previous studies have acknowledged that the TIM-3 pathway is involved in the pathogenesis of several human autoimmune diseases, such as systemic lupus erythematous, rheumatoid arthritis and aplastic anaemia. Moreover, genetic data suggest a role for TIM-3 in human autoimmune diseases. However, in immune thrombocytopenia (ITP), a common Th1- and possibly Th17-biased autoimmune disorder, the role of TIM-3 has not been explored. Recently, our data have demonstrated that TIM-3 expression is reduced in ITP patients, and we have found a potential link between ITP and the TIM-3 pathway. In this article, we discuss and speculate on the role of the TIM-3 pathway in ITP.

Association of T-cell immunoglobulin and mucin domain-containing molecule 3 (Tim-3) polymorphisms with susceptibility and disease progression of HBV infection

PURPOSE

T-cell immunoglobulin and mucin domain-containing molecule 3 (Tim-3) plays an important role in regulating T cells in hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). However, few researches have reported the association of Tim-3 genetic variants with susceptibility and progression of HBV infection. In this study, we focused on the association of Tim-3 polymorphisms with HBV infection, HBsAg seroclearance and hepatocellular carcinoma.

METHODS

A total of 800 subjects were involved in this study. Four groups were studied here, including HBV, HBsAg seroclearance, HBV-associated HCC and healthy controls. Three single-nucleotide polymorphisms (SNPs) of Tim-3, rs246871, rs25855 and rs31223 were genotyped to analyze the association of Tim-3 polymorphisms with susceptibility and disease progression of HBV infection.

RESULTS

Our study found that rs31223 and rs246871 were associated with disease progression of HBV infection, while none of the three SNPs was relevant to HBV susceptibility. The minor allele "C" of rs31223 was found to be associated with an increased probability of HBsAg seroclearance (P = 0.033) and genotype "CC" of rs246871 to be associated with an increased probability of HBV-associated HCC (P = 0.007). In accordance, haplotypic analysis of the three polymorphisms also showed that the haplotype block CGC* and TGC* were significantly associated with HBsAg seroclearance (P<0.05) while haplotype block CAT*, CGT*, TAC* and TGT* were significantly associated with HBV-associated HCC (all P<0.05).

CONCLUSIONS

Genetic variants of Tim-3 have an important impact on disease progression of HBV infection. With specific Tim-3 polymorphisms, patients infected with HBV could be potential candidates of HCC and HBsAg seroclearance.

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.

Immune derangement occurs in patients with H7N9 avian influenza

INTRODUCTION

Currently, little is known about the immunological characteristics of patients with avian influenza A (H7N9) virus infection.

METHODS

The numbers and percentages of peripheral blood immune cells were measured in 27 patients with laboratory-confirmed H7N9 virus infection and 30 healthy controls (HCs). The functional phenotypes of T cells and monocytes, as well as serum cytokine levels, were analyzed by flow cytometry.

RESULTS

There were 19 patients (70.4%) with acute respiratory distress syndrome, 13 (48.1%) with secondary respiratory infection, 20 (74%) with systemic inflammatory response syndrome (SIRS; defined as having at least two concurrent SIRS components), 18 (66.7%) with lymphocytopenia and 11 (40.7%) with reduced numbers of monocytes. In comparison with levels in the HCs, the levels of serum interleukin 6 (IL-6), IL-8 and IL-10 and the percentages of CD38+ or Tim-3+ T cells were significantly increased. However, the percentages of human leukocyte antigen-DR + and Tim-3+ monocytes were significantly decreased in patients compared with HCs.

CONCLUSIONS

Patients with avian H7N9 virus infection display profound SIRS concomitantly with an anti-inflammatory response, which may be associated with the rapid progression of and high mortality associated with this novel viral disease.

Tim-3 directly enhances CD8 T cell responses to acute Listeria monocytogenes infection

T cell Ig and mucin domain (Tim) 3 is a surface molecule expressed throughout the immune system that can mediate both stimulatory and inhibitory effects. Previous studies have provided evidence that Tim-3 functions to enforce CD8 T cell exhaustion, a dysfunctional state associated with chronic stimulation. In contrast, the role of Tim-3 in the regulation of CD8 T cell responses to acute and transient stimulation remains undefined. To address this knowledge gap, we examined how Tim-3 affects CD8 T cell responses to acute Listeria monocytogenes infection. Analysis of wild-type (WT) mice infected with L. monocytogenes revealed that Tim-3 was transiently expressed by activated CD8 T cells and was associated primarily with acquisition of an effector phenotype. Comparison of responses to L. monocytogenes by WT and Tim-3 knockout (KO) mice showed that the absence of Tim-3 significantly reduced the magnitudes of both primary and secondary CD8 T cell responses, which correlated with decreased IFN-γ production and degranulation by Tim-3 KO cells stimulated with peptide Ag ex vivo. To address the T cell-intrinsic role of Tim-3, we analyzed responses to L. monocytogenes infection by WT and Tim-3 KO TCR-transgenic CD8 T cells following adoptive transfer into a shared WT host. In this setting, the accumulation of CD8 T cells and the generation of cytokine-producing cells were significantly reduced by the lack of Tim-3, demonstrating that this molecule has a direct effect on CD8 T cell function. Combined, our results suggest that Tim-3 can mediate a stimulatory effect on CD8 T cell responses to an acute infection.

Expression of TIM-3 on CD4+ and CD8+ T cells in the peripheral blood and synovial fluid of rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by a chronic inflammatory process that targets the synovial lining of diarthrodial joints. TIM-3 plays a key role in the negative regulation of the immune response. In this study, we investigated the expression of TIM-3 on CD4+ and CD8+ T cells from systemic (peripheral blood) and local (synovial fluid) perspectives of RA. Level of TIM-3+ cells from peripheral blood and synovial fluid of patients as well as peripheral blood of healthy controls was measured by flow cytometry. Results showed that TIM-3 expression was significantly increased in both CD4+ and CD8+ T cells in the peripheral blood of RA (p < 0.001 and p < 0.001, respectively). Furthermore, patients revealed even higher expression of TIM-3 in CD4+ and CD8+ T cells in synovial fluid than in peripheral blood. When comparing TIM-3 level with the severity of RA, we identified that the percentage of TIM-3 on both peripheral CD4+ and peripheral CD8+ T cells was negatively correlated with disease activity score 28 (DAS28) of the patients. Similarly, TIM-3 on synovial fluid CD4+ and CD8+ T cells also revealed inverse correlation with DAS28 of the cases. Our data demonstrate a negative correlation between TIM-3 and the disease progression of RA.

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.

Tim-3 on peripheral CD4⁺ and CD8⁺ T cells is involved in the development of glioma

Tim-3 acts as a negative regulatory molecule and plays a critical role in immune tolerance. The purpose of this study was to investigate the expression of Tim-3 on peripheral CD4⁺ and CD8⁺ T cells in glioma. A total of 30 newly diagnosed glioma patients and 30 healthy controls were recruited and leukocytes from peripheral blood mononuclear cells were analyzed for Tim-3 surface expression by flow cytometry. Plasma tumor necrosis factor-alpha (TNF-α) was also measured. Data showed that expression of Tim-3 was significantly increased in both CD4⁺ and CD8⁺ T cells in glioma patients than in controls (p<0.001 and p<0.001, respectively). Patients with a higher tumor grade revealed further elevated Tim-3 expression in CD8⁺ T cells compared with those with a lower tumor grade. Also, the Karnofsky score of patients was negatively correlated with the percentage of Tim-3⁺CD8⁺ T cells in glioma patients (p=0.007). In addition, an inverse correlation was observed between the plasma level of TNF-α and Tim-3⁺CD4⁺ T cells (p=0.005) or Tim-3⁺CD8⁺ T cells (p<0.001) in glioma patients. Our results suggested that Tim-3 may be involved in the development of glioma.

Comparison of dynamic expressions of Tim-3 and PD-1 in the brains between toxoplasmic encephalitis-resistant BALB/c and -susceptible C57BL/6 mice

T cells and IFN-γ are essential for controlling the reactivation of toxoplasmic encephalitis (TE), regardless of whether mice are susceptible or resistant to TE. It has been demonstrated that CD8(+) T cells exhausted in chronic Toxoplasma gondii infection result in TE reactivation in C57BL/6 mice. However, this phenomenon had not been reported in genetically TE-resistant BALB/c mice. To explore the immune mechanism of TE in different backgrounds of mice, the dynamic expressions of Tim-3, programmed cell death 1 (PD-1), and their ligands (galectin-9, PD-L1, PD-L2) in brain tissues were compared between TE-resistant BALB/c and -susceptible C57BL/6 mice infected with Prugniaud (Pru, a type II strain) of T. gondii in this study. Compared with infected BALB/c mice, there were remarkable pathological changes with significantly higher histological scores in the brains of C57BL/6 mice at 14, 35, 50, and 70 days postinfection (p.i., P < 0.01); significantly increased mRNA expressions of Tim-3 at 35 (P < 0.05) and 70 (P < 0.01) days p.i.; and significantly increased PD-1 at all the times p.i. (P < 0.01) in the brains of infected C57BL/6 mice. Furthermore, there were significantly increased mRNA expressions of PD-L1 in the brain of C57BL/6 mice than that in BALB/c mice at all the times p.i. (P < 0.01). Although the mRNA expressions of galectin-9 (ligand of Tim-3) were increased in the brains of both lineages of mice at all the times p.i., it showed no differences between the two lineages of mice. Our data suggest that the differences of Tim-3 and PD-1/PD-L1 expressions may contribute to the different immune responses between TE-resistant BALB/c and -susceptible C57BL/6 mice infected with Pru strain of T. gondii.

Galectin-9 signaling through TIM-3 is involved in neutrophil-mediated Gram-negative bacterial killing: an effect abrogated within the cystic fibrosis lung

The T cell Ig and mucin domain-containing molecule (TIM) family of receptors have emerged as potential therapeutic targets to correct abnormal immune function in chronic inflammatory conditions. TIM-3 serves as a functional receptor in structural cells of the airways and via the ligand galectin-9 (Gal-9) can modulate the inflammatory response. The aim of this study was to investigate TIM-3 expression and function in neutrophils, focusing on its potential role in cystic fibrosis (CF) lung disease. Results revealed that TIM-3 mRNA and protein expression values of circulating neutrophils were equal between healthy controls (n = 20) and people with CF (n = 26). TIM-3 was detected on resting neutrophil membranes by FACS analysis, and expression levels significantly increased post IL-8 or TNF-α exposure (p < 0.05). Our data suggest a novel role for TIM-3/Gal-9 signaling involving modulation of cytosolic calcium levels. Via TIM-3 interaction, Gal-9 induced neutrophil degranulation and primed the cell for enhanced NADPH oxidase activity. Killing of Pseudomonas aeruginosa was significantly increased upon bacterial opsonization with Gal-9 (p < 0.05), an effect abrogated by blockade of TIM-3 receptors. This mechanism appeared to be Gram-negative bacteria specific and mediated via Gal-9/ LPS binding. Additionally, we have demonstrated that neutrophil TIM-3/Gal-9 signaling is perturbed in the CF airways due to proteolytic degradation of the receptor. In conclusion, results suggest a novel neutrophil defect potentially contributing to the defective bacterial clearance observed in the CF airways and suggest that manipulation of the TIM-3 signaling pathway may be of therapeutic value in CF, preferably in conjunction with antiprotease treatment.

Galectin-9 enhances cytokine secretion, but suppresses survival and degranulation, in human mast cell line

Galectin-9 (Gal-9), a lectin having a β-galactoside-binding domain, can induce apoptosis of Th1 cells by binding to TIM-3. In addition, Gal-9 inhibits IgE/Ag-mediated degranulation of mast cell/basophilic cell lines by binding to IgE, thus blocking IgE/Ag complex formation. However, the role of Gal-9 in mast cell function in the absence of IgE is not fully understood. Here, we found that recombinant Gal-9 directly induced phosphorylation of Erk1/2 but not p38 MAPK in a human mast cell line, HMC-1, which does not express FcεRI. Gal-9 induced apoptosis and inhibited PMA/ionomycin-mediated degranulation of HMC-1 cells. On the other hand, Gal-9 induced cytokine and/or chemokine production by HMC-1 cells, dependent on activation of ERK1/2 but not p38 MAPK. In addition, the lectin activity of Gal-9 was required for Gal-9-mediated cytokine secretion by HMC-1 cells. These observations suggest that Gal-9 has dual properties as both a regulator and an activator of mast cells.

Protective role for Toll-like receptor-9 in the development of atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

Atherosclerosis is driven by inflammatory reactions that are shared with the innate immune system. Toll-like receptor-9 (TLR9) is an intracellular pattern recognition receptor of the innate immune system that is currently under clinical investigation as a therapeutic target in inflammatory diseases. Here, we investigated whether TLR9 has a role in the development of atherosclerosis in apolipoprotein E-deficient (ApoE(-/-)) mice.

APPROACH AND RESULTS

Newly generated double-knockout ApoE(-/-):TLR9(-/-) mice and control ApoE(-/-) mice were fed a high-fat diet from 8 weeks and effects on lesion size, cellular composition, inflammatory status, and plasma lipids were assessed after 8, 12, 15, and 20 weeks. All 4 time points demonstrated exacerbated atherosclerotic lesion severity in ApoE(-/-):TLR9(-/-) mice, with a corresponding increase in lipid deposition and accumulation of macrophages, dendritic cells, and CD4(+) T cells. Although ApoE(-/-):TLR9(-/-) mice exhibited an increase in plasma very low-density lipoprotein/low-density-lipoprotein cholesterol, the very low-density lipoprotein/low-density lipoprotein:high-density lipoprotein ratio was unaltered because of a parallel increase in plasma high-density lipoprotein cholesterol. As a potential mechanism accounting for plaque progression in ApoE(-/-):TLR9(-/-) mice, CD4(+) T-cell accumulation was further investigated and depletion of these cells in ApoE(-/-):TLR9(-/-) mice significantly reduced lesion severity. As a final translational approach, administration of a TLR9 agonist (type B CpG oligodeoxynucleotide 1668) to ApoE(-/-) mice resulted in a reduction of lesion severity.

CONCLUSIONS

Genetic deletion of the innate immune receptor TLR9 exacerbated atherosclerosis in ApoE(-/-) mice fed a high-fat diet. CD4(+) T cells were identified as potential mediators of this effect. A type B CpG oligodeoxynucleotide TLR9 agonist reduced lesion severity, thus identifying a novel therapeutic approach in atherosclerosis.

Hierarchical and selective roles of galectins in hepatocarcinogenesis, liver fibrosis and inflammation of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents a global health problem. Infections with hepatitis B or C virus, non-alcoholic steatohepatitis disease, alcohol abuse, or dietary exposure to aflatoxin are the major risk factors to the development of this tumor. Regardless of the carcinogenic insult, HCC usually develops in a context of cirrhosis due to chronic inflammation and advanced fibrosis. Galectins are a family of evolutionarily-conserved proteins defined by at least one carbohydrate recognition domain with affinity for β-galactosides and conserved sequence motifs. Here, we summarize the current literature implicating galectins in the pathogenesis of HCC. Expression of "proto-type" galectin-1, "chimera-type" galectin-3 and "tandem repeat-type" galectin-4 is up-regulated in HCC cells compared to their normal counterparts. On the other hand, the "tandem-repeat-type" lectins galectin-8 and galectin-9 are down-regulated in tumor hepatocytes. The abnormal expression of these galectins correlates with tumor growth, HCC cell migration and invasion, tumor aggressiveness, metastasis, postoperative recurrence and poor prognosis. Moreover, these galectins have important roles in other pathological conditions of the liver, where chronic inflammation and/or fibrosis take place. Galectin-based therapies have been proposed to attenuate liver pathologies. Further functional studies are required to delineate the precise molecular mechanisms through which galectins contribute to HCC.

T cell Ig and mucin domain-containing protein 3 is recruited to the immune synapse, disrupts stable synapse formation, and associates with receptor phosphatases

CD8(+) CTLs are adept at killing virally infected cells and cancer cells and releasing cytokines (e.g., IFN-γ) to aid this response. However, during cancer and chronic viral infections, such as with HIV, this CTL response is progressively impaired due to a process called T cell exhaustion. Previous work has shown that the glycoprotein T cell Ig and mucin domain-containing protein 3 (Tim-3) plays a functional role in establishing T cell exhaustion. Tim-3 is highly upregulated on virus and tumor Ag-specific CD8(+) T cells, and antagonizing Tim-3 helps restore function of CD8(+) T cells. However, very little is known of how Tim-3 signals in CTLs. In this study, we assessed the role of Tim-3 at the immunological synapse as well as its interaction with proximal TCR signaling molecules in primary human CD8(+) T cells. Tim-3 was found within CD8(+) T cell lipid rafts at the immunological synapse. Blocking Tim-3 resulted in a significantly greater number of stable synapses being formed between Tim-3(hi)CD8(+) T cells and target cells, suggesting that Tim-3 plays a functional role in synapse formation. Further, we confirmed that Tim-3 interacts with Lck, but not the phospho-active form of Lck. Finally, Tim-3 colocalizes with receptor phosphatases CD45 and CD148, an interaction that is enhanced in the presence of the Tim-3 ligand, galectin-9. Thus, Tim-3 interacts with multiple signaling molecules at the immunological synapse, and characterizing these interactions could aid in the development of therapeutics to restore Tim-3-mediated immune dysfunction.

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.

Tim-3: an activation marker and activation limiter of innate immune cells

Tim-3 was initially identified on activated Th1, Th17, and Tc1 cells and induces T cell death or exhaustion after binding to its ligand, Gal-9. The observed relationship between dysregulated Tim-3 expression on T cells and the progression of many clinical diseases has identified this molecule as an important target for intervention in adaptive immunity. Recent data have shown that it also plays critical roles in regulating the activities of macrophages, monocytes, dendritic cells, mast cells, natural killer cells, and endothelial cells. Although the underlying mechanisms remain unclear, dysregulation of Tim-3 expression on these innate immune cells leads to an excessive or inhibited inflammatory response and subsequent autoimmune damage or viral or tumor evasion. In this review, we focus on the expression and function of Tim-3 on innate immune cells and discuss (1) how Tim-3 is expressed and regulated on different innate immune cells; (2) how it affects the activity of different innate immune cells; and (3) how dysregulated Tim-3 expression on innate immune cells affects adaptive immunity and disease progression. Tim-3 is involved in the optimal activation of innate immune cells through its varied expression. A better understanding of the physiopathological role of the Tim-3 pathway in innate immunity will shed new light on the pathogenesis of clinical diseases, such as autoimmune diseases, chronic viral infections, and cancer, and suggest new approaches to intervention.

Galectin-9 prolongs the survival of septic mice by expanding Tim-3-expressing natural killer T cells and PDCA-1+ CD11c+ macrophages

INTRODUCTION

Galectin-9 ameliorates various inflammatory conditions including autoimmune diseases by regulating T cell and macrophage/dendritic cell (DC) functions. However, the effect of galectin-9 on polymicrobial sepsis has not been assessed.

METHODS

We induced polymicrobial sepsis by cecal ligation and puncture (CLP) in mice. The survival rate was compared between galectin-9- and PBS-treated CLP mice. An ELISA was used to compare the levels of various cytokines in the plasma and culture supernatants. Fluorescence-activated cell sorting analysis was further performed to compare the frequencies of subpopulations of spleen cells.

RESULTS

Galectin-9 exhibited a protective effect in polymicrobial sepsis as demonstrated in galetin-9 transgenic mice and therapeutic galectin-9 administration. In contrast, such effect was not observed in nude mice, indicating the involvement of T cells in galectin-9-mediated survival prolongation. Galectin-9 decreased TNFα, IL-6, IL-10 and, high mobility group box 1 (HMGB1) and increased IL-15 and IL-17 plasma and spleen levels. Galectin-9 increased the frequencies of natural killer T (NKT) cells and PDCA-1+ CD11c+ macrophages (pDC-like macrophages) but did not change the frequency of CD4 or CD8 T cells, γδT cells or conventional DC. As expected, galectin-9 decreased the frequency of Tim-3+ CD4 T cells, most likely Th1 and Th17 cells. Intriguingly, many spleen NK1.1+ NKT cells and pDC-like macrophages expressed Tim-3. Galectin-9 increased the frequency of Tim-3-expressing NK1.1+ NKT cells and pDC-like macrophages. Galectin-9 further increased IL-17+ NK1.1+ NKT cells.

CONCLUSION

These data suggest that galectin-9 exerts therapeutic effects on polymicrobial sepsis, possibly by expanding NKT cells and pDC-like macrophages and by modulating the production of early and late proinflammatory cytokines.

Increased expression of T cell immunoglobulin and mucin domain 3 aggravates brain inflammation via regulation of the function of microglia/macrophages after intracerebral hemorrhage in mice

Background

Microglia/macrophages are known to play important roles in initiating brain inflammation after spontaneous intracerebral hemorrhage (ICH). T cell immunoglobulin and mucin domain-3 (Tim-3) have been proven to play a critical part in several inflammatory diseases through regulation of both adaptive and innate immune responses. Tim-3 can be expressed by microglia/macrophages and regulates their function in the innate immune response. However, the effect of Tim-3 on inflammatory responses following ICH is unclear.

Methods

In this study, we investigated Tim-3 expression, the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and brain water content in peri-hematomal brain tissue at 12 hours and at 1, 3, 5, and 7 days post-ICH in wild type (WT) ICH and Tim-3^−/− ICH mice. The numbers of Tim-3 positive cells,astrocytes, neutrophils and microglia/macrophages were detected using immunofluorescence staining. Cytokines were measured by ELISA. Double immunoflurorescence labeling was performed to identify the cellular source of Tim-3 expression. Mouse neurological deficit scores were assessed through animal behavior.

Results

Expression of Tim-3 increased early in mouse peri-hematomal brain tissue after autologous blood injection, peaked at day 1, and was positively correlated with the concentrations of TNF-α, IL-1β, and brain water content. Tim-3 was predominantly expressed in microglia/macrophages. Compared with WT mice, Tim-3^−/− mice had reduced ICH-induced brain inflammation with decreased TNF-α and IL-1β, cerebral edema and neurological deficit scores. Moreover, Tim-/- inhibited activation of microglia/macrophages. The number of activated microglia/macrophages in Tim-3^−/− ICH mice was much lower than that in WT ICH mice.

Conclusions

Our findings demonstrate that Tim-3 plays an important role in brain inflammation after ICH, and may be a potential treatment target.

T cell immunoglobulin domain and mucin domain-3 as an emerging target for immunotherapy in cancer management

Cancer-induced immunosuppression significantly impacts tumors, rendering them the ability to acquire aggressive and treatment-resistant phenotypes. The recent clinical success of drugs targeting the immunosuppressive machinery of tumors highlights the importance of identifying novel drugs that effectively augment antitumor immunity and elicit clinical remission in advanced tumors. T cell immunoglobulin domain and mucin domain-3 (TIM-3) is a critical immunoregulatory molecule that links pattern recognition-mediated innate sensing with antigen-specific immune responses. Recent evidence has elucidated the potential utility of drugs targeting TIM-3 in inducing antitumor responses, particularly in synergy with conventional anticancer regimens. Herein, we provide a comprehensive overview, as well as future perspectives, regarding the role of TIM-3 as an emerging target that may improve clinical responses for cancer patients.

Do inhibitory immune receptors play a role in the etiology of autoimmune disease?

Inhibitory receptors are thought to be important in balancing immune responses. The general assumption is that lack of inhibition predisposes for autoimmune diseases. As reviewed here, various experimental and clinical data support this assumption. However, in humans genetic evidence implicates only a limited number of inhibitory receptors. GWAS have established common variation in a few inhibitory receptor genes, such as FCγRIIB, PD-1 and CTLA-4 as risk factors. The question arises whether inhibitory receptor function is a major determinant of autoimmune disease. In this respect, the finding that genetic variation in CSK and PTPN22 is strongly associated with multiple autoimmune diseases is of interest. We propose a model in which the molecules encoded by these genes are downstream of inhibitory receptors. We conclude that common genetic variation of inhibitory receptors, with few exceptions, is not a determining factor for autoimmunity in humans. However, common downstream signaling pathways are.

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.

Galectin-9 plasma levels reflect adverse hematological and immunological features in acute dengue virus infection

BACKGROUND

Dengue virus (DENV) infection remains a major public health burden worldwide. Soluble mediators may play a critical role in the pathogenesis of acute DENV infection. Galectin-9 (Gal-9) is a soluble β-galactoside-binding lectin, with multiple immunoregulatory and inflammatory properties.

OBJECTIVE

To investigate plasma Gal-9 levels as a biomarker for DENV infection.

STUDY DESIGN

We enrolled 65 DENV infected patients during the 2010 epidemic in the Philippines and measured their plasma Gal-9 and cytokine/chemokine levels, DENV genotypes, and copy number during the critical and recovery phases of illness.

RESULTS

During the critical phase, Gal-9 levels were significantly higher in DENV infected patients compared to healthy or those with non-dengue febrile illness. The highest Gal-9 levels were observed in dengue hemorrhagic fever (DHF) patients (DHF: 2464 pg/ml; dengue fever patients (DF): 1407 pg/ml; non-dengue febrile illness: 616 pg/ml; healthy: 196 pg/ml). In the recovery phase, Gal-9 levels significantly declined from peak levels in DF and DHF patients. Gal-9 levels tracked viral load, and were associated with multiple cytokines and chemokines (IL-1α, IL-8, IP-10, and VEGF), including monocyte frequencies and hematologic variables of coagulation. Further discriminant analyses showed that eotaxin, Gal-9, IFN-α2, and MCP-1 could detect 92% of DHF and 79.3% of DF, specifically (P<0.01).

CONCLUSION

Gal-9 appears to track DENV inflammatory responses, and therefore, it could serve as an important novel biomarker of acute DENV infection and disease severity.

A disintegrin and metalloprotease (ADAM) 10 and ADAM17 are major sheddases of T cell immunoglobulin and mucin domain 3 (Tim-3)

T cell immunoglobulin and mucin domain 3 (Tim-3) dampens the response of CD4(+) and CD8(+) effector T cells via induction of cell death and/or T cell exhaustion and enhances the ability of macrophages to clear pathogens via binding to galectin 9. Here we provide evidence that human Tim-3 is a target of A disintegrin and metalloprotease (ADAM)-mediated ectodomain shedding resulting in a soluble form of Tim-3. We identified ADAM10 and ADAM17 as major sheddases of Tim-3 as shown by ADAM-specific inhibitors and the ADAM10 pro-domain in HEK293 cells and ADAM10/ADAM17-deficient murine embryonic fibroblasts. PMA-induced shedding of Tim-3 was abrogated by deletion of amino acids Glu(181)-Asp(190) of the stalk region and Tim-3 lacking the intracellular domain was not efficiently cleaved after PMA stimulation. Surprisingly, a single lysine residue within the intracellular domain rescues shedding of Tim-3. Shedding of endogenous Tim-3 was found in primary human CD14(+) monocytes after PMA and ionomycin stimulation. Importantly, the recently described down-regulation of Tim-3 from Toll-like receptor-activated CD14(+) monocytes was caused by ADAM10- and ADAM17-mediated shedding. Inhibition of Tim-3 shedding from lipopolysaccharide-induced monocytes did not influence lipopolysaccharide-induced TNFα and IL-6 but increases IL-12 expression. In summary, we describe Tim-3 as novel target for ADAM-mediated ectodomain shedding and suggest a role of Tim-3 shedding in TLR-mediated immune responses of CD14(+) monocytes.

Emerging concepts in immunity to hepatitis C virus infection

Since the discovery of hepatitis C virus (HCV) by molecular cloning almost a quarter of a century ago, unprecedented at the time because the virus had never been grown in cell culture or detected serologically, there have been impressive strides in many facets of our understanding of the natural history of the disease, the viral life cycle, the pathogenesis, and antiviral therapy. It is apparent that the virus has developed multiple strategies to evade immune surveillance and eradication. This Review covers what we currently understand of the temporal and spatial immunological changes within the human innate and adaptive host immune responses that ultimately determine the outcomes of HCV infection.

Tim-3 is differently expressed in genetically susceptible C57BL/6 and resistant BALB/c mice during oral infection with Toxoplasma gondii

Tim-3 has opposing roles in innate and adaptive immunities. It not only dampens CD4+ and CD8+ T cells responses but also enhances the ability of macrophages to eliminate intracellular pathogens. After peroral infection with 100 cysts of Toxoplasma gondii genetically susceptible C57BL/6 mice develop an unchecked Th1 response associated with the development of small intestinal immunopathology. Here we report that upon infection with T. gondii, both susceptible C57BL/6 and resistant BALB/c mice exhibit increased frequencies of Tim-3+ cells in spleens and mesenteric lymph nodes. The number of Tim-3+ cells was significantly higher in C57BL/6 than in BALB/c mice. Tim-3 was expressed by macrophages, dendritic, natural killer, as well as CD4+ and CD8+ T cells. Highest frequencies of Tim-3+ cells were observed at the peak of Th1 responses (day 7 post infection) concurrent with the development of ileal immunopathology. Infected Tim-3-deficient BALB/c mice did not develop ileal immunopathology nor did their parasite loads differ from those in wildtype BALB/c mice. Thus, although Tim-3 is markedly upregulated upon infection and differentially regulated in susceptible and resistant mice upon infection with T. gondii, the absence of Tim-3 is not sufficient to overcome the genetic resistance of BALB/c mice to the development of Th1-driven small intestinal immunopathology.

TIM-3 as a novel therapeutic target for eradicating acute myelogenous leukemia stem cells

Acute myelogenous leukemia (AML) originates from self-renewing leukemic stem cells (LSCs), which represent the ultimate therapeutic target for AML. Recent studies have identified several AML LSC-specific surface antigens as candidate targets of therapeutic molecules. T cell immunoglobulin mucin-3 (TIM-3) is expressed on LSCs in most types of AML, with the exception of acute promyelocytic leukemia, but not on normal hematopoietic stem cells (HSCs). In xenograft models reconstituted with human AML LSCs or HSCs, an anti-human TIM-3 mouse IgG2a antibody with cytotoxic activities eradicates AML LSCs in vivo, but does not affect normal human hematopoiesis. Thus, TIM-3 is a promising therapeutic target for the eradication of AML LSCs.

Combined TIM-3 blockade and CD137 activation affords the long-term protection in a murine model of ovarian cancer

Background

T-cell immunoglobulin and mucin domain 3 (TIM-3) is known as a negative immune regulator and emerging data have implicated TIM-3 a pivotal role in suppressing antitumor immunity. The co-stimulatory receptor CD137 is transiently upregulated on T-cells following activation and increases their proliferation and survival when engaged. Although antagonistic anti-TIM-3 or agonistic anti-CD137 antibodies can promote the rejection of several murine tumors, some poorly immunogenic tumors were refractory to this treatment. In this study, we sought to evaluate whether combined TIM-3 blockade and CD137 activation would significantly improve the immunotherapy in the murine ID8 ovarian cancer model.

Methods

Mice with established ID8 tumor were intraperitoneally injected with single or combined anti-TIM-3/CD137 monoclonal antibody (mAb); mice survival was recorded, the composition and gene expression of tumor-infiltrating immune cells in these mice was analyzed by flow cytometry and quantitative RT-PCR respectively, and the function of CD8⁺ cells was evaluated by ELISA and cytotoxicity assay.

Results

Either anti-TIM-3 or CD137 mAb alone, although effective in 3 days established tumor, was unable to prevent tumor progression in mice bearing 10 days established tumor, however, combined anti-TIM-3/CD137 mAb significantly inhibited the growth of these tumors with 60% of mice tumor free 90 days after tumor inoculation. Therapeutic efficacy was associated with a systemic immune response with memory and antigen specificity, required CD4⁺ cells and CD8⁺ cells. The 2 mAb combination increased CD4⁺ and CD8⁺ cells and decreased immunosuppressive CD4⁺FoxP3⁺ regulatory T (Treg) cells and CD11b⁺Gr-1⁺ myeloid suppressor cells (MDSC) at tumor sites, giving rise to significantly elevated ratios of CD4⁺ and CD8⁺ cells to Treg and MDSC; This is consistent with biasing local immune response towards an immunostimulatory Th1 type and is further supported by quantitative RT-PCR data showing the increased Th1-associated genes by anti-TIM-3/CD137 treatment. The increased CD8⁺ T cells produced high level of IFN-γ upon tumor antigen stimulation and displayed antigen-specific cytotoxic activity.

Conclusions

To our knowledge, this is the first report investigating the effects of anti-TIM-3/CD137 combined mAb in a murine ovarian cancer model, and our results may aid the design of future trials for ovarian cancer immunotherapy.

A novel soluble form of Tim-3 associated with severe graft-versus-host disease

The T cell Ig and mucin domain 3 (Tim-3) receptor has been implicated as a negative regulator of adaptive immune responses. We have utilized a proteomic strategy to identify novel proteins associated with graft versus host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). Mass spectrometry analysis of plasma from subjects with mid-gut and upper-gut GVHD compared with those without GVHD identified increased levels of a protein identified with high confidence as Tim-3. A follow-up validation study using an immunoassay to measure Tim-3 levels in individual plasma samples from 127 patients demonstrated significantly higher plasma Tim-3 concentrations in patients with the more severe mid-gut GVHD, compared with those with upper-gut GVHD (P = .005), patients without GVHD (P = .002), and normal controls (P < .0001). Surface expression of Tim-3 was increased on CD8(+) T cells from patients with grade 2 to 4 acute GVHD (P = .01). Mass spectrometry-based profiling of plasma from multiple subjects diagnosed with common diseases provided evidence for restricted release of soluble Tim-3 in the context of GVHD. These findings have mechanistic implications for the development of novel strategies for targeting the Tim-3 immune regulatory pathway as an approach to improving control of GVHD.

T-cell immunoglobulin and mucin domain 3 acts as a negative regulator of atherosclerosis

OBJECTIVE

Atherosclerosis is a chronic autoimmune-like disease in which lipids and fibrous elements accumulate in the arterial blood vessels. T cells are present within atherosclerotic plaques, and their activation is partially dependent on costimulatory signals, which can either provide positive or negative signals that promote T-cell activation or limit T-cell responses, respectively. T-cell immunoglobulin and mucin domain 3 (Tim-3) is a coinhibitory type 1 transmembrane protein that affects the function of several immune cells involved in atherosclerosis, such as monocytes, macrophages, effector T cells, and regulatory T cells. In the present study, we determined the role of Tim-3 in the development of atherosclerosis.

APPROACH AND RESULTS

Western-type diet-fed low-density lipoprotein receptor-deficient (LDLr(-/-)) mice were treated with an anti-Tim-3 antibody for 3 and 8 weeks. Anti-Tim-3 administration increased fatty streak formation with 66% and increased atherosclerotic plaque formation after 8 weeks with 35% in the aortic root and with 50% in the aortic arch. Furthermore, blockade of Tim-3 signaling increased percentages of circulating monocytes with 33% and lesional macrophages with 20%. In addition, anti-Tim-3 administration increased CD4(+) T cells with 17%, enhanced their activation status, and reduced percentages of regulatory T cells with 18% and regulatory B cells with 37%.

CONCLUSIONS

It is known that Tim-3 acts as a negative regulator of both innate and adaptive immune responses, and in the present study, we show that anti-Tim-3 treatment augments lesion development, accompanied by an increase in the number of monocytes/macrophages and CD4(+) T cells and by decreased regulatory T cells and regulatory B cells.

Cis association of galectin-9 with Tim-3 differentially regulates IL-12/IL-23 expressions in monocytes via TLR signaling

Human monocytes/macrophages (M/M_Ф) of the innate immunity sense and respond to microbial products via specific receptor coupling with stimulatory (such as TLR) and inhibitory (such as Tim-3) receptors. Current models imply that Tim-3 expression on M/M_Ø can deliver negative signaling to TLR-mediated IL-12 expression through trans association with its ligand Galectin-9 (Gal-9) presented by other cells. However, Gal-9 is also expressed within M/M_Ø, and the effect of intracellular Gal-9 on Tim-3 activities and inflammatory responses in the same M/M_Ø remains unknown. In this study, our data suggest that Tim-3 and IL-12/IL-23 gene transcriptions are regulated by enhanced or silenced Gal-9 expression within monocytes through synergizing with TLR signaling. Additionally, TLR activation facilitates Gal-9/Tim-3 cis association within the same M/M_Ø to differentially regulate IL-12/IL-23 expressions through STAT-3 phosphorylation. These results reveal a ligand (Gal-9) compartment-dependent regulatory effect on receptor (Tim-3) activities and inflammatory responses via TLR pathways—a novel mechanism underlying cellular responses to external or internal cues.

Role of Tim-3 in pathogenesis of inflammatory diseases of the digestive system

T cell immunoglobulin mucin domain-containing molecules (Tim)-3 is a type I cell membrane glycoprotein that is expressed on the surface of cells involved in innate and adaptive immunity. As the first discovered member of Tim family, Tim-3 participates in T cell-induced immune responses. By interacting with its ligands galectin-9 or PtdSer, Tim-3 induces cell apoptosis and clearance of apoptotic cells in autoimmune disorders, allergic diseases and virus infection-associated diseases. Tim-3 can act as a negative regulator of Th1/Th17 immune responses. Current research has shown that Tim-3 is involved in the pathogenesis of inflammatory diseases of the digestive system. Here we will review the progress in understanding the role of Tim-3 in the pathogenesis of inflammatory diseases of the digestive system.

Proinflammatory stimuli induce galectin-9 in human mesenchymal stromal cells to suppress T-cell proliferation

Human multipotent mesenchymal stromal cells (MSCs) are clinically applied to treat autoimmune diseases and graft-versus-host disease due to their immunomodulatory properties. Several molecules have been identified to mediate these effects, including constitutively expressed galectin-1. However, there are indications in the literature that MSCs exert enhanced immunosuppressive functions after interaction with an inflammatory environment. Therefore, we analyzed how inflammatory stimuli influence the expression of the galectin network in MSCs and functionally tested the relevance for the immunomodulatory effects of MSCs. We found that galectin-9 was strongly induced in MSCs upon interaction with activated PBMCs. Proinflammatory cytokines, such as interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α), and also ligands of the Toll-like receptors (TLRs) TLR2, TLR3, and TLR4 elicited similar induction of galectin-9 in activated PBMCs. Galectin-9 was not only upregulated intracellularly, but also released by MSCs in significant amounts into the supernatant after exposure to proinflammatory stimuli. In proliferation assays, MSCs with a galectin-9 knockdown lost a significant portion of their antiproliferative effects on T cells. In conclusion, we found that unlike constitutively expressed galectin-1, galectin-9 is induced by several proinflammatory stimuli and released by MSCs. Thus, galectin-9 contributes to the inducible immunomodulatory functions of MSCs.