Galectin-9 suppresses the generation of Th17, promotes the induction of regulatory T cells, and regulates experimental autoimmune arthritis

Dendritic cell control of tolerogenic responses

One of the most fundamental problems in immunology is the seemingly schizophrenic ability of the immune system to launch robust immunity against pathogens, while acquiring and maintaining a state of tolerance to the body's own tissues and the trillions of commensal microorganisms and food antigens that confront it every day. A fundamental role for the innate immune system, particularly dendritic cells (DCs), in orchestrating immunological tolerance has been appreciated, but emerging studies have highlighted the nature of the innate receptors and the signaling pathways that program DCs to a tolerogenic state. Furthermore, several studies have emphasized the major role played by cellular interactions and the microenvironment in programming tolerogenic DCs. Here, we review these studies and suggest that the innate control of tolerogenic responses can be viewed as different hierarchies of organization, in which DCs, their innate receptors and signaling networks, and their interactions with other cells and local microenvironments represent different levels of the hierarchy.

Costimulatory pathways in transplantation

Secondary, so-called costimulatory, signals are critically required for the process of T cell activation. Since landmark studies defined that T cells receiving a T cell receptor signal without a costimulatory signal, are tolerized in vitro, the investigation of T cell costimulation has attracted intense interest. Early studies demonstrated that interrupting T cell costimulation allows attenuation of the alloresponse, which is particularly difficult to modulate due to the clone size of alloreactive T cells. The understanding of costimulation has since evolved substantially and now encompasses not only positive signals involved in T cell activation but also negative signals inhibiting T cell activation and promoting T cell tolerance. Costimulation blockade has been used effectively for the induction of tolerance in rodent models of transplantation, but turned out to be less potent in large animals and humans. In this overview we will discuss the evolution of the concept of T cell costimulation, the potential of 'classical' and newly identified costimulation pathways as therapeutic targets for organ transplantation as well as progress towards clinical application of the first costimulation blocking compound.

Glycan recognition at the interface of the intestinal immune system: target for immune modulation via dietary components

The intestinal mucosa is constantly exposed to the luminal content, which includes micro-organisms and dietary components. Prebiotic non-digestible oligosaccharides may be supplemented to the diet to exert modulation of immune responses in the intestine. Short chain galacto- and long chain fructo-oligosaccharides (scGOS/lcFOS), functionally mimicking oligosaccharides present in human milk, have been reported to reduce the development of allergy through modulation of the intestinal microbiota and immune system. Nonetheless, the underlying working mechanisms of scGOS/lcFOS are unclear. Intestinal epithelial cells lining the mucosa are known to express carbohydrate (glycan)-binding receptors that may be involved in modulation of the mucosal immune response. This review aims to provide an overview of glycan-binding receptors, in particular galectins, which are expressed by intestinal epithelial cells and immune cells. In addition, their involvement in health and disease will be addressed, especially in food allergy and inflammatory bowel disease, diseases originating from the gastro-intestinal tract. Insight in the recognition of glycans in the intestinal tract may open new avenues for the treatment of intestinal inflammatory diseases by either nutritional concepts or pharmacological intervention.

Therapeutic potential of Galectin-9 in human disease

In recent years, an important role has emerged for the glycan-binding protein Galectin-9 (Gal-9) in health and disease. In normal physiology, Gal-9 seems to be a pivotal modulator of T-cell immunity by inducing apoptosis in specific T-cell subpopulations. Because these T-cell populations are associated with autoimmunity, inflammatory disease, and graft rejection, it was postulated that application of exogenous Gal-9 may limit pathogenic T-cell activity. Indeed, treatment with recombinant Gal-9 ameliorates disease activity in various preclinical models of autoimmunity and allograft graft rejection. In many solid cancers, the loss of Gal-9 expression is closely associated with metastatic progression. In line with this observation, treatment with recombinant Gal-9 prevents metastatic spread in various preclinical cancer models. In addition, various hematological malignancies are sensitive to apoptotic elimination by recombinant Gal-9. Here, we review the biology and physiological role of this versatile lectin and discuss the therapeutic potential of Gal-9 in various diseases, including autoimmunity, asthma, infection, and cancer.

Tim-3 negatively regulates IL-12 expression by monocytes in HCV infection

T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) is a newly identified negative immunomodulator that is up-regulated on dysfunctional T cells during viral infections. The expression and function of Tim-3 on human innate immune responses during HCV infection, however, remains poorly characterized. In this study, we report that Tim-3 is constitutively expressed on human resting CD14⁺ monocyte/macrophages (M/M_Ø) and functions as a cap to block IL-12, a key pro-inflammatory cytokine linking innate and adaptive immune responses. Tim-3 expression is significantly reduced and IL-12 expression increased upon stimulation with Toll-like receptor 4 (TLR4) ligand - lipopolysaccharide (LPS) and TLR7/8 ligand - R848. Notably, Tim-3 is over-expressed on un-stimulated as well as TLR-stimulated M/M_Ø, which is inversely associated with the diminished IL-12 expression in chronically HCV-infected individuals when compared to healthy subjects. Up-regulation of Tim-3 and inhibition of IL-12 are also observed in M/M_Ø incubated with HCV-expressing hepatocytes, as well as in primary M/M_Ø or monocytic THP-1 cells incubated with HCV core protein, an effect that mimics the function of complement C1q and is reversible by blocking the HCV core/gC1qR interaction. Importantly, blockade of Tim-3 signaling significantly rescues HCV-mediated inhibition of IL-12, which is primarily expressed by Tim-3 negative M/M_Ø. Tim-3 blockade reduces HCV core-mediated expression of the negative immunoregulators PD-1 and SOCS-1 and increases STAT-1 phosphorylation. Conversely, blocking PD-1 or silencing SOCS-1 gene expression also decreases Tim-3 expression and enhances IL-12 secretion and STAT-1 phosphorylation. These findings suggest that Tim-3 plays a crucial role in negative regulation of innate immune responses, through crosstalk with PD-1 and SOCS-1 and limiting STAT-1 phosphorylation, and may be a novel target for immunotherapy to HCV infection.

Endogenous galectin-1 and acute inflammation: emerging notion of a galectin-9 pro-resolving effect

The role of endogenous galectin-1 (Gal-1) in acute inflammation has been poorly investigated. We therefore performed the carrageenan-induced paw edema model in wild-type and Gal-1(-/-) mice. On subplantar injection of carrageenan, Gal-1(-/-) mice displayed a similar first phase of edema (≤24 hours) to wild-type mice; however, a much less pronounced second phase (48 to 96 hours) was evident in this genotype. This reduced inflammation was associated with lower paw expression of inflammatory genes and cell infiltrates. Analysis of galectin protein and mRNA expression revealed high expression of Gal-1 in wild-type paws during resolution (≥48 hours), with some expression of galectin-9 (Gal-9). Administration of stable Gal-1 to wild-type mice completely ablated the first phase of edema but was ineffective when administered therapeutically at the 24-hour time point. Conversely, Gal-9 administration did not alter the first phase of edema but significantly reduced the second phase when administered therapeutically. This suggests anti-inflammatory actions for both proteins in this model albeit at different phases of the inflammatory response. Collectively, these data indicate that the absence of endogenous Gal-1 results in an abrogated response during the second phase of the edema reaction.

Galectin-9 attenuates acute lung injury by expanding CD14- plasmacytoid dendritic cell-like macrophages

RATIONALE

Galectin (Gal)-9 plays a crucial role in the modulation of innate and adaptive immunity.

OBJECTIVES

To investigate whether Gal-9 plays a role in a murine acute lung injury (ALI) model.

METHODS

C57BL/6 mice were pretreated with Gal-9 by subcutaneous injection 24 and 48 hours before intranasal LPS inoculation.

MEASUREMENTS AND MAIN RESULTS

Gal-9 suppressed pathological changes of ALI induced by LPS. Gal-9 reduced levels of proinflammatory cytokines and chemokines, such as tumor necrosis factor (TNF)-α, IL-1β, IL-6, and keratinocyte-derived cytokine; decreased neutrophils; and increased IL-10 and CD11b(+)Gr-1(+) macrophages in the bronchoalveolar lavage fluid of ALI mice. In Gal-9-deficient mice, pathological changes of ALI were exaggerated, and the number of neutrophils and the TNF-α level were increased. CD11b(+)Gr-1(+) cells were increased in the spleen of both Gal-9-treated and phosphate-buffered saline (PBS)-treated ALI mice, but only Gal-9 increased the ability of CCR2-expressing macrophages to migrate toward monocyte chemoattractant protein-1. Transfer of CD11b(+)Gr-1(+) macrophages obtained from Gal-9-treated mice ameliorated ALI. CD11b(+)Gr-1(+) macrophages obtained from Gal-9-treated but not PBS-treated mice suppressed TNF-α and keratinocyte-derived cytokine production from LPS-stimulated macrophages, and down-regulated Toll-like receptor-4 (TLR4) and TLR2 expression on thioglycollate-elicited macrophages. Fluorescence-activated cell-sorting analysis revealed that CD14 is negligible on CD11b(+)Gr-1(+) macrophages obtained from Gal-9-treated mice, although those from both groups resembled plasmacytoid dendritic cells (pDCs). Gal-9 down-regulated CD14 on pDC-like macrophages from PBS-treated mice independently of Gal-9/Tim-3 (T-cell immunoglobulin- and mucin domain-containing molecule-3) interaction, resulting in the acquisition of suppressive function, suggesting that the loss of CD14 by Gal-9 is critical for the suppression of pDC-like macrophages.

CONCLUSIONS

Gal-9 attenuates ALI by expanding CD14(-)CD11b(+)Gr-1(+) pDC-like macrophages by preferentially suppressing macrophage functions to release proinflammatory cytokines through TLR4 and TLR2 down-regulation.

T-cell immunoglobulin and mucin domain 3 genetic polymorphisms are associated with rheumatoid arthritis independent of a shared epitope status

The aim of this study was to investigate T-cell immunoglobulin and mucin domain 3 (TIM3) genetic polymorphisms and rheumatoid arthritis (RA) according to the shared epitope (SE) status. Six single nucleotide polymorphisms (SNPs: rs11742259 [C/T], rs10515746 [C/A], rs35960726 [A/G], rs1036199 [A/C], rs4704846 [A/G], and rs11134551 [A/G]) in the TIM3 gene from 366 RA patients and 389 healthy controls were investigated using the real-time polymerase chain reaction method. Associations between these SNPs and clinical manifestations (including SE status) were investigated using the SPSS program and Haploview. Polymorphisms of rs35690726 (AG+ GG vs AA: 8.2% vs 1.8%, p(c) < 0.001) were significantly associated with RA with or without SE (p(c) < 0.001 or p(c) = 0.009, respectively). Polymorphisms of rs11742259 (p(c) = 0.003) and rs1036199 (p(c) = 0.012) were significantly different in RA patients with SE, but not in those without SE. In haplotype analysis with a permutation test for the first 4 SNPs (rs11742259, rs10515746, rs35690726, and, rs1036199), CCAA, CCGA, CCGC, and CAAA haplotypes were significantly associated with RA. The clinical characteristics of RA patients were not significantly associated with any TIM3 polymorphism. TIM3 genetic polymorphisms may have a role in the development of RA regardless of a shared epitope status.

Expression of human TIM-3 and its correlation with disease activity in rheumatoid arthritis

OBJECTIVE

T-cell immunoglobulin- and mucin-domain-containing molecule 3 (TIM-3) is a novel transmembrane protein that is involved in the regulation of T-helper 1 (Th1)-cell-mediated immunity. This study was undertaken to investigate the expressions of TIM-3 and its ligand galectin 9 (Gal-9) with respect to disease activity in rheumatoid arthritis (RA).

METHODS

Blood was collected from 39 RA patients and 31 healthy controls. Blood leucocyte TIM-3 and Gal-9 mRNA levels and RA disease activity were determined. Synovial tissue (ST) from five RA patients and five osteoarthritis (OA) patients were examined for TIM-3 mRNA expression and were also analysed for TIM-3 by immunohistology.

RESULTS

TIM-3 mRNA expression was significantly higher in the ST of RA patients than in the ST of OA patients. TIM-3 was expressed in the synovial sublining area in ST of RA patients but not in OA ST. TIM-3 mRNA expression from peripheral blood mononuclear cells (PBMCs) of RA patients was negatively correlated with the 28-joint Disease Activity Score (DAS28). Gal-9 mRNA level in PBMCs of RA patients was higher than in healthy controls, and was significantly higher in patients with low disease activity compared to those with moderate to high disease activity. Gal-9 mRNA expression in PBMCs of RA patients was positively correlated with forkhead box P3 (FoxP3) mRNA expression.

CONCLUSION

TIM-3 and its interaction with Gal-9 are closely associated with RA disease activity and may play an important role in the pathogenesis of RA. In addition to the negative regulatory effect of Gal-9 mediated through the TIM-3-Gal-9 pathway, Gal-9 may exert its suppressive effect on RA disease activity by modulation of regulatory T (Treg) cells.

Galectin-9 administration ameliorates CVB3 induced myocarditis by promoting the proliferation of regulatory T cells and alternatively activated Th2 cells

In this study we explored the effects of galectin-9 on CVB3 induced myocarditis and its possible mechanisms involved. We demonstrated that galectin-9 expression was significantly up-regulated in the myocardium following CVB3 infection and was correlated with the severity of viral myocarditis. To explore whether galectin-9 may have therapeutic effect on the CVB3 induced myocarditis, galectin-9 was administered daily to mice following CVB3 infection. Significantly reduced CD4(+) T cells and remarkably increased regulatory T cells frequency in the heart tissue were found as compared to the non-treated mice. It was accompanied by a significant decreased level of Th1 cytokines as TNF-α and IFN-γ both in the myocardium and serum, and an increased level of Th2 cytokines such as IL-4 and IL-10. Galectin-9 was further found to promote the proliferation of regulatory T cells and elevated IL-4-secreting Th2 cells. It may represent as a novel therapeutic strategy in treating Th1-mediated inflammatory cardiac disease.

Galectin 3 aggravates joint inflammation and destruction in antigen-induced arthritis

OBJECTIVE

Galectin 3, an endogenous β-galactoside-binding lectin, plays an important role in the modulation of immune responses. The finding that galectin 3 is present in the inflamed synovium in patients with rheumatoid arthritis suggests that the protein is associated with the pathogenesis of this disease. We undertook this study to investigate the influence of galectin 3 deficiency in a murine model of arthritis.

METHODS

Wild-type (WT) and galectin 3-deficient (galectin 3(-/-) ) mice were subjected to antigen-induced arthritis (AIA) through immunization with methylated bovine serum albumin. The concentration of serum cytokines (interleukin-6 [IL-6] and tumor necrosis factor α [TNFα]) and antigen-specific antibodies was evaluated using a cytometric bead array platform and enzyme-linked immunosorbent assay (ELISA). Cellular IL-17 responses were examined by flow cytometry, ELISA, and enzyme-linked immunospot assay.

RESULTS

The joint inflammation and bone erosion of AIA were markedly suppressed in galectin 3(-/-) mice as compared with WT mice. The reduced arthritis in galectin 3(-/-) mice was accompanied by decreased levels of antigen-specific IgG and proinflammatory cytokines. The frequency of IL-17-producing cells in the spleen was reduced in galectin 3(-/-) mice as compared with WT mice. Exogenously added recombinant galectin 3 could partially restore the reduced arthritis and cytokines in galectin 3(-/-) mice.

CONCLUSION

Our findings show that galectin 3 plays a pathogenic role in the development and progression of AIA and that the disease severity is accompanied by alterations of antigen-specific IgG levels, systemic levels of TNFα and IL-6, and frequency of IL-17-producing T cells. To our knowledge, this is the first report of in vivo evidence that galectin 3 plays a crucial role in the development of arthritis.

Coexpression of Tim-3 and PD-1 identifies a CD8+ T-cell exhaustion phenotype in mice with disseminated acute myelogenous leukemia

Tumor-associated immune suppression can lead to defective T cell-mediated antitumor immunity. Here, we identified a unique phenotype of exhausted T cells in mice with advanced acute myelogenous leukemia (AML). This phenotype is characterized by the coexpression of Tim-3 and PD-1 on CD8(+) T cells in the liver, the major first site of AML metastases. PD-1 and Tim-3 coexpression increased during AML progression. PD-1(+)Tim-3(+) CD8(+) T cells were deficient in their ability to produce IFN-γ, TNF-α, and IL-2 in response to PD-1 ligand (PDL1) and Tim-3 ligand (galectin-9) expressing AML cells. PD-1 knockout (KO), which were partially resistant to AML challenge, up-regulated Tim-3 during AML progression and such Tim-3(+)PD-1- KO CD8(+) T cells had reduced cytokine production. Galectin-9 KO mice were more resistant to AML, which was associated with reduced T-regulatory cell accumulation and a modest induction of PD-1 and Tim-3 expression on CD8(+) T cells. Whereas blocking the PD-1/PDL1 or Tim-3/galectin-9 pathway alone was insufficient to rescue mice from AML lethality, an additive effect was seen in reducing-albeit not eliminating-both tumor burden and lethality when both pathways were blocked. Therefore, combined PD-1/PDL1 and Tim-3/galectin-9 blockade may be beneficial in preventing CD8(+) T-cell exhaustion in patients with hematologic malignancies such as advanced AML.

Polymorphisms of the TIM-1 and TIM-3 genes are not associated with systemic lupus erythematosus in a Chinese population

Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune diseases, which affects multiple organ systems such as kidney. The imbalance of T-helper 1 (Th1)/Th2 cells is critical in the pathogenesis of SLE. The T-cell immunoglobulin mucin (TIM) proteins comprise a family of cell surface molecules expressed on T cells that regulate Th1- and Th2-cell-mediated immunity. Recent work has found increased expression of TIM-1 and TIM-3 ligand (galactin-9) mRNA in SLE patients and implied that TIM proteins might be involved in the pathogenesis of SLE. In this study, genotyping of single-nucleotide polymorphisms (SNPs) was performed for TIM-1 (rs1501909 and rs12522248) and TIM-3 (rs9313439 and rs10515746) in 202 SLE patients and 217 healthy individuals in a Chinese population. Results showed no significant differences existed between the patients with SLE and the controls as well as SLE patients with nephritis and those without nephritis, in all four SNPs. The findings suggest that the polymorphisms of TIM gene family might not contribute to SLE susceptibility in the Chinese population. However, it should be noted that the statistical power of our study is relatively low, which likely did not have adequate power to detect the actual correlation between the selected SNPs and SLE susceptibility; moreover, we cannot discard a possible association of other variants within the region covering TIM with SLE as a genetic risk factor, with larger samples in different populations.

Increased Tim-3 expression on peripheral lymphocytes from patients with rheumatoid arthritis negatively correlates with disease activity

Tim-3 has been reported as an important regulatory molecule and plays a pivotal role in several autoimmunity diseases. Here, we demonstrated the increased expression of Tim-3 on peripheral CD4(+) T, CD8(+) T, NKT cells and monocytes from RA patients compared to those from healthy controls. Percentage of Tim-3(+) cells in peripheral blood mononuclear cells (PBMCs) showed an inverse correlation with disease activity score 28 (DAS28) and plasma TNF-α level. Similar negative correlations were found between disease activity and Tim-3 levels on CD4(+) T, CD8(+) T and NKT cells. Consistently, Tim-3 expression on CD3(+) T cells was further increased in patients with disease remission after treatment. Tim-3 expression on CD8(+) T and NKT cells negatively correlates with plasma TNF-α. Our results suggest that Tim-3 might participate in the proceeding of RA by its negative regulation on various T cell subsets. Tim-3 might be a potential new marker for assessing severity of RA.

Dysregulation of TIM-3-galectin-9 pathway in the cystic fibrosis airways

The T-cell Ig and mucin domain-containing molecules (TIMs) have emerged as promising therapeutic targets to correct abnormal immune function in several autoimmune and chronic inflammatory conditions. It has been reported that proinflammatory cytokine dysregulation and neutrophil-dominated inflammation are the main causes of morbidity in cystic fibrosis (CF). However, the role of TIM receptors in CF has not been investigated. In this study, we demonstrated that TIM-3 is constitutively overexpressed in the human CF airway, suggesting a link between CF transmembrane conductance regulator (CFTR) function and TIM-3 expression. Blockade of CFTR function with the CFTR inhibitor-172 induced an upregulation of TIM-3 and its ligand galectin-9 in normal bronchial epithelial cells. We also established that TIM-3 serves as a functional receptor in bronchial epithelial cells, and physiologically relevant concentrations of galectin-9 induced TIM-3 phosphorylation, resulting in increased IL-8 production. In addition, we have demonstrated that both TIM-3 and galectin-9 undergo rapid proteolytic degradation in the CF lung, primarily because of neutrophil elastase and proteinase-3 activity. Our results suggest a novel intrinsic defect that may contribute to the neutrophil-dominated immune response in the CF airways.

Fine-tuning antitumor responses through the control of galectin-glycan interactions: an overview

In recent years, we have witnessed critical advances in genomics and proteomics which contributed to delineate the "tumor progression signature". This includes the altered expression of genes and proteins not only in tumor cells, but also in tumor-associated stromal, endothelial, and immune cells. Adding more complexity to this bewildering information, efforts are being made to define the "glycosylation signature" of the tumor microenvironment, which results from the abnormal expression and activity of glycosyltransferases, glycosidases, and enzyme chaperons. The multiple combinatorial possibilities of glycan structures expressed by neoplastic versus normal tissue provide enormous potential for information display and expand potential therapeutic opportunities. The responsibility of deciphering the biological information encoded by the tumor-associated glycome is partially assigned, to distinct families of endogenous glycan-binding proteins or lectins, whose expression and function are regulated in cancerous tissues. Galectins, a family of evolutionarily conserved glycan-binding proteins, can control tumor progression by directly influencing tumor growth or by modulating cell migration, angiogenesis, and tumor-immune escape. In this review, we will highlight recent findings on how galectin-glycan lattices control the dialogue between tumor and immune cells and how these interactions could be exploited for therapeutic purposes.

Galectin-9 regulates T helper cell function independently of Tim-3

β-Galactoside-binding lectin 9 (galectin-9) is a tandem repeat-type member of the galectin family. It was initially characterized as an eosinophil chemoattractant and an inducer of apoptosis in thymocytes. Subsequently, galectin-9 was identified as a ligand for transmembrane immunoglobulin mucin domain 3 (Tim-3), a type I glycoprotein induced on T cells during chronic inflammation. Work in autoimmune diseases and chronic viral infections have led to the current hypothesis that the function of Tim-3 is to limit immune responses. However, it is still not known to what degree these effects are due to the galectin-9/Tim-3 interaction. In this study, we show that galectin-9 is not limited to the role of a pro-apoptotic agent, but that it can also induce the production of pro-inflammatory cytokines from T helper cells. This effect is dose-dependent and does not require Tim-3. These findings suggest that the effects of galectin-9 on T cells are more complex than previously thought and are mediated by additional receptors apart from Tim-3.

X-ray structures of human galectin-9 C-terminal domain in complexes with a biantennary oligosaccharide and sialyllactose

Galectin-9, a tandem-repeat-type β-galactoside-specific animal lectin with two carbohydrate recognition domains (CRDs) at the N- and C-terminal ends, is involved in chemoattraction, apoptosis, and the regulation of cell differentiation and has anti-allergic effects. Its ability to recognize carbohydrates is essential for its biological functions. Human galectin-9 (hG9) has high affinity for branched N-glycan-type oligosaccharides (dissociation constants of 0.16-0.70 μM) and linear β1-3-linked poly-N-acetyllactosamines (0.09-8.3 μM) and significant affinity for the α2-3-sialylated oligosaccharides (17-34 μM). Further, its N-terminal CRD (hG9N) and C-terminal CRD (hG9C) differ in specificity. To elucidate this unique feature of hG9, x-ray structures of hG9C in the free form and in complexes with N-acetyllactosamine, the biantennary pyridylaminated oligosaccharide, and α2-3-sialyllactose were determined. They are the first x-ray structural analysis of C-terminal CRD of the tandem-repeat-type galectin. The results clearly revealed the mechanism by which branched and α2-3-sialylated oligosaccharides are recognized and explained the difference in specificity between hG9N and hG9C. Based on structural comparisons with other galectins, we propose that the wide entrance for ligand binding and the shallow binding site of hG9C are favorable for branched oligosaccharides and that Arg(221) is responsible for recognizing sialylated oligosaccharides.

The inhibition of the T-cell immunoglobulin and mucin domain 3 (Tim3) pathway enhances the efficacy of tumor vaccine

T-cell immunoglobulin and mucin domain 3 (Tim3) plays an important role in the Th1-mediated immune response; however, its effect on the efficacy of tumor vaccines has not been fully evaluated. Here, we demonstrate the effect of Tim3 pathway inhibition on tumor growth in mice. Lewis lung carcinoma (3LL) cells expressing a Tim3 pathway inhibitor, when injected into mice, showed suppressed tumor growth and a reduced frequency of CD4(+)CD25(+)Foxp3(+) T-cells. Furthermore, Tim3 pathway inhibition significantly enhanced the efficacy of a prophylactic tumor vaccine and marginally enhanced the efficacy of a therapeutic tumor vaccine. However, when given in combination with the chemotherapeutic agent, 5-fluorouracil, the therapeutic tumor vaccine capable of Tim3 pathway inhibition had no additional anti-tumor effect. Our results show that Tim3 pathway inhibition can enhance tumor vaccine efficacy.

TIM-3: a novel regulatory molecule of alloimmune activation

T cell Ig domain and mucin domain (TIM)-3 has previously been established as a central regulator of Th1 responses and immune tolerance. In this study, we examined its functions in allograft rejection in a murine model of vascularized cardiac transplantation. TIM-3 was constitutively expressed on dendritic cells and natural regulatory T cells (Tregs) but only detected on CD4(+)FoxP3(-) and CD8(+) T cells in acutely rejecting graft recipients. A blocking anti-TIM-3 mAb accelerated allograft rejection only in the presence of host CD4(+) T cells. Accelerated rejection was accompanied by increased frequencies of alloreactive IFN-γ-, IL-6-, and IL-17-producing splenocytes, enhanced CD8(+) cytotoxicity against alloantigen, increased alloantibody production, and a decline in peripheral and intragraft Treg/effector T cell ratio. Enhanced IL-6 production by CD4(+) T cells after TIM-3 blockade plays a central role in acceleration of rejection. Using an established alloreactivity TCR transgenic model, blockade of TIM-3 increased allospecific effector T cells, enhanced Th1 and Th17 polarization, and resulted in a decreased frequency of overall number of allospecific Tregs. The latter is due to inhibition in induction of adaptive Tregs rather than prevention of expansion of allospecific natural Tregs. In vitro, targeting TIM-3 did not inhibit nTreg-mediated suppression of Th1 alloreactive cells but increased IL-17 production by effector T cells. In summary, TIM-3 is a key regulatory molecule of alloimmunity through its ability to broadly modulate CD4(+) T cell differentiation, thus recalibrating the effector and regulatory arms of the alloimmune response.

Tim3 binding to galectin-9 stimulates antimicrobial immunity

The interaction between Tim3 on Th1 cells and galectin-9 on Mycobacterium tuberculosis–infected macrophages restricts the bacterial growth by stimulating caspase-1–dependent IL-1β secretion.

T cell immunoglobulin and mucin domain 3 (Tim3) is a negative regulatory molecule that inhibits effector T_H1-type responses. Such inhibitory signals prevent unintended tissue inflammation, but can be detrimental if they lead to premature T cell exhaustion. Although the role of Tim3 in autoimmunity has been extensively studied, whether Tim3 regulates antimicrobial immunity has not been explored. Here, we show that Tim3 expressed on T_H1 cells interacts with its ligand, galectin-9 (Gal9), which is expressed by Mycobacterium tuberculosis–infected macrophages to restrict intracellular bacterial growth. Tim3–Gal9 interaction leads to macrophage activation and stimulates bactericidal activity by inducing caspase-1–dependent IL-1β secretion. We propose that the T_H1 cell surface molecule Tim3 has evolved to inhibit growth of intracellular pathogens via its ligand Gal9, which in turn inhibits expansion of effector T_H1 cells to prevent further tissue inflammation.

Grape seed proanthocyanidin extract (GSPE) differentially regulates Foxp3(+) regulatory and IL-17(+) pathogenic T cell in autoimmune arthritis

Grape seed proanthocyanidin extract (GSPE), which is the antioxidant derived from grape seeds, has been reported to possess a variety of potent properties. We have previously shown that GSPE attenuates collagen-induced arthritis. However the mechanism by which GSPE regulates the immune response remains unclear, although it may involve effects on the regulation of pathogenic T cells in autoimmune arthritis. To clarify this issue, we have assessed the effects of GSPE on differential regulation of Th17 and regulatory T (Treg) cells subsets in vitro in mouse and human CD4(+) T cells. We observed that GSPE decreased the frequency of IL-17(+)CD4(+)Th17 cells and increased induction of CD4(+)CD25(+)forkhead box protein 3 (Foxp3)(+) Treg cells. In vivo, GSPE effectively attenuated clinical symptoms of established collagen-induced arthritis in mice with concomitant suppression of IL-17 production and enhancement of Foxp3 expression (type II collagen-reactive Treg cells) in CD4(+) T cells of joints and splenocytes. The presence of GSPE decreased the levels of IL-21, IL-22, IL-26 and IL-17 production by human CD4(+) T cells in a STAT3-dependent manner. In contrast, GSPE induces Foxp3(+) Treg cells in humans. Our results suggest that GSPE possesses a reciprocal control over IL-17 and Foxp3. By potently regulating inflammatory T cell differentiation, GSPE may serve as a possible novel therapeutic agent for inflammatory and autoimmune diseases, including rheumatoid arthritis.

TIM genes: a family of cell surface phosphatidylserine receptors that regulate innate and adaptive immunity

The TIM (T cell/transmembrane, immunoglobulin, and mucin) gene family plays a critical role in regulating immune responses, including allergy, asthma, transplant tolerance, autoimmunity, and the response to viral infections. The unique structure of TIM immunoglobulin variable region domains allows highly specific recognition of phosphatidylserine (PtdSer), exposed on the surface of apoptotic cells. TIM-1, TIM-3, and TIM-4 all recognize PtdSer but differ in expression, suggesting that they have distinct functions in regulating immune responses. TIM-1, an important susceptibility gene for asthma and allergy, is preferentially expressed on T-helper 2 (Th2) cells and functions as a potent costimulatory molecule for T-cell activation. TIM-3 is preferentially expressed on Th1 and Tc1 cells, and generates an inhibitory signal resulting in apoptosis of Th1 and Tc1 cells. TIM-3 is also expressed on some dendritic cells and can mediate phagocytosis of apoptotic cells and cross-presentation of antigen. In contrast, TIM-4 is exclusively expressed on antigen-presenting cells, where it mediates phagocytosis of apoptotic cells and plays an important role in maintaining tolerance. TIM molecules thus provide a functional repertoire for recognition of apoptotic cells, which determines whether apoptotic cell recognition leads to immune activation or tolerance, depending on the TIM molecule engaged and the cell type on which it is expressed.

TIM genes: a family of cell surface phosphatidylserine receptors that regulate innate and adaptive immunity

The TIM (T cell/transmembrane, immunoglobulin, and mucin) gene family plays a critical role in regulating immune responses, including allergy, asthma, transplant tolerance, autoimmunity, and the response to viral infections. The unique structure of TIM immunoglobulin variable region domains allows highly specific recognition of phosphatidylserine (PtdSer), exposed on the surface of apoptotic cells. TIM-1, TIM-3, and TIM-4 all recognize PtdSer but differ in expression, suggesting that they have distinct functions in regulating immune responses. TIM-1, an important susceptibility gene for asthma and allergy, is preferentially expressed on T-helper 2 (Th2) cells and functions as a potent costimulatory molecule for T-cell activation. TIM-3 is preferentially expressed on Th1 and Tc1 cells, and generates an inhibitory signal resulting in apoptosis of Th1 and Tc1 cells. TIM-3 is also expressed on some dendritic cells and can mediate phagocytosis of apoptotic cells and cross-presentation of antigen. In contrast, TIM-4 is exclusively expressed on antigen-presenting cells, where it mediates phagocytosis of apoptotic cells and plays an important role in maintaining tolerance. TIM molecules thus provide a functional repertoire for recognition of apoptotic cells, which determines whether apoptotic cell recognition leads to immune activation or tolerance, depending on the TIM molecule engaged and the cell type on which it is expressed.

Th17 cells: the emerging reciprocal partner of regulatory T cells in the liver

T helper cells that produce interleukin-17 (IL-17) (Th17 cells) have recently been identified as the third distinct subset of effector T cells, the differentiation of which depends on specific transcription nuclear factor retinoic acid-related orphan nuclear receptor-gammat. Emerging data have suggested that Th17 cells play an important role in innate immunity, adaptive immunity and autoimmunity. Interestingly, there is a reciprocal relationship between Th17 cells and regulatory T cells (Treg), not only in development, but also in their effector function. Transforming growth factor (TGF)-beta induces Treg-specific transcription factor Forkhead box P3(FOXP3), while the addition of IL-6 to TGF-beta inhibits the generation of Treg cells and induces Th17 cells. It is proposed that the fine balance between Th17 and Treg cells is crucial for maintenance of immune homeostasis. In addition to IL-6, other factors such as retinoic acid, rapamycin, or cytokines (e.g., IL-2 and IL-27) could dictate the balance between Th17 and Treg cells. Since Treg cells play an important role in hepatic immunity with overregulation in chronic viral hepatitis and hepatic carcinoma, and inadequate inhibition in autoimmune liver diseases, graft rejection and acute liver failure, it is reasonable to assume that Th17 cells may play a reciprocal role in these diseases. Thus, future research on the Treg/Th17 balance may provide an opportunity to illustrate the pathogenesis of hepatic inflammation and to explore new therapeutic targets for immune-related liver diseases.

Galectin-9/TIM-3 interaction regulates virus-specific primary and memory CD8 T cell response

In this communication, we demonstrate that galectin (Gal)-9 acts to constrain CD8(+) T cell immunity to Herpes Simplex Virus (HSV) infection. In support of this, we show that animals unable to produce Gal-9, because of gene knockout, develop acute and memory responses to HSV that are of greater magnitude and better quality than those that occur in normal infected animals. Interestingly, infusion of normal infected mice with alpha-lactose, the sugar that binds to the carbohydrate-binding domain of Gal-9 limiting its engagement of T cell immunoglobulin and mucin (TIM-3) receptors, also caused a more elevated and higher quality CD8(+) T cell response to HSV particularly in the acute phase. Such sugar treated infected mice also had expanded populations of effector as well as memory CD8(+) T cells. The increased effector T cell responses led to significantly more efficient virus control. The mechanisms responsible for the outcome of the Gal-9/TIM-3 interaction in normal infected mice involved direct inhibitory effects on TIM-3(+) CD8(+) T effector cells as well as the promotion of Foxp3(+) regulatory T cell activity. Our results indicate that manipulating galectin signals, as can be achieved using appropriate sugars, may represent a convenient and inexpensive approach to enhance acute and memory responses to a virus infection.

Galectin-9/TIM-3 interaction regulates virus-specific primary and memory CD8 T cell response

In this communication, we demonstrate that galectin (Gal)-9 acts to constrain CD8(+) T cell immunity to Herpes Simplex Virus (HSV) infection. In support of this, we show that animals unable to produce Gal-9, because of gene knockout, develop acute and memory responses to HSV that are of greater magnitude and better quality than those that occur in normal infected animals. Interestingly, infusion of normal infected mice with alpha-lactose, the sugar that binds to the carbohydrate-binding domain of Gal-9 limiting its engagement of T cell immunoglobulin and mucin (TIM-3) receptors, also caused a more elevated and higher quality CD8(+) T cell response to HSV particularly in the acute phase. Such sugar treated infected mice also had expanded populations of effector as well as memory CD8(+) T cells. The increased effector T cell responses led to significantly more efficient virus control. The mechanisms responsible for the outcome of the Gal-9/TIM-3 interaction in normal infected mice involved direct inhibitory effects on TIM-3(+) CD8(+) T effector cells as well as the promotion of Foxp3(+) regulatory T cell activity. Our results indicate that manipulating galectin signals, as can be achieved using appropriate sugars, may represent a convenient and inexpensive approach to enhance acute and memory responses to a virus infection.

T cell Ig and mucin domain proteins and immunity

Proteins of the transmembrane (or T cell) Ig and mucin domain (TIM) family are expressed by multiple cell types within the immune systems of rodents and humans. Studies over the last several years have suggested that these proteins may be promising targets for therapeutic manipulation of immune responses. This review discusses the progress that has been made in understanding TIM protein function in the immune system, as well as some of the unresolved issues that remain on the road to eventually targeting TIM proteins for enhancing or inhibiting immunity.

Galectin-9 exhibits anti-myeloma activity through JNK and p38 MAP kinase pathways

Galectins constitute a family of lectins that specifically exhibit the affinity for beta-galactosides and modulate various biological events. Galectin-9 is a tandem-repeat type galectin with two carbohydrate recognition domains and has recently been shown to have an anti-proliferative effect on cancer cells. We investigated the effect of recombinant protease-resistant galectin-9 (hGal9) on multiple myeloma (MM). In vitro, hGal9 inhibited the cell proliferation of five myeloma cell lines examined, including a bortezomib-resistant subcell line, with IC(50) between 75.1 and 280.0 nM, and this effect was mediated by the induction of apoptosis with the activation of caspase-8, -9, and -3. hGal9-activated Jun NH(2)-terminal kinase (JNK) and p38 MAPK signaling pathways followed by H2AX phosphorylation. Importantly, the inhibition of either JNK or p38 MAPK partly inhibited the anti-proliferative effect of hGal9, indicating the crucial role of these pathways in the anti-MM effect of hGal9. hGal9 also induced cell death in patient-derived myeloma cells, some with poor-risk factors, such as chromosomal deletion of 13q or translocation t(4;14)(p16;q32). Finally, hGal9 potently inhibited the growth of human myeloma cells xenografted in nude mice. These suggest that hGal9 is a new therapeutic target for MM that may overcome resistance to conventional chemotherapy.

A crucial role for Kupffer cell-derived galectin-9 in regulation of T cell immunity in hepatitis C infection

Approximately 200 million people throughout the world are infected with hepatitis C virus (HCV). One of the most striking features of HCV infection is its high propensity to establish persistence (approximately 70-80%) and progressive liver injury. Galectins are evolutionarily conserved glycan-binding proteins with diverse roles in innate and adaptive immune responses. Here, we demonstrate that galectin-9, the natural ligand for the T cell immunoglobulin domain and mucin domain protein 3 (Tim-3), circulates at very high levels in the serum and its hepatic expression (particularly on Kupffer cells) is significantly increased in patients with chronic HCV as compared to normal controls. Galectin-9 production from monocytes and macrophages is induced by IFN-gamma, which has been shown to be elevated in chronic HCV infection. In turn, galectin-9 induces pro-inflammatory cytokines in liver-derived and peripheral mononuclear cells; galectin-9 also induces anti-inflammatory cytokines from peripheral but not hepatic mononuclear cells. Galectin-9 results in expansion of CD4(+)CD25(+)FoxP3(+)CD127(low) regulatory T cells, contraction of CD4(+) effector T cells, and apoptosis of HCV-specific CTLs. In conclusion, galectin-9 production by Kupffer cells links the innate and adaptive immune response, providing a potential novel immunotherapeutic target in this common viral infection.

A crucial role for Kupffer cell-derived galectin-9 in regulation of T cell immunity in hepatitis C infection

Approximately 200 million people throughout the world are infected with hepatitis C virus (HCV). One of the most striking features of HCV infection is its high propensity to establish persistence (∼70–80%) and progressive liver injury. Galectins are evolutionarily conserved glycan-binding proteins with diverse roles in innate and adaptive immune responses. Here, we demonstrate that galectin-9, the natural ligand for the T cell immunoglobulin domain and mucin domain protein 3 (Tim-3), circulates at very high levels in the serum and its hepatic expression (particularly on Kupffer cells) is significantly increased in patients with chronic HCV as compared to normal controls. Galectin-9 production from monocytes and macrophages is induced by IFN-γ, which has been shown to be elevated in chronic HCV infection. In turn, galectin-9 induces pro-inflammatory cytokines in liver-derived and peripheral mononuclear cells; galectin-9 also induces anti-inflammatory cytokines from peripheral but not hepatic mononuclear cells. Galectin-9 results in expansion of CD4⁺CD25⁺FoxP3⁺CD127^low regulatory T cells, contraction of CD4⁺ effector T cells, and apoptosis of HCV-specific CTLs. In conclusion, galectin-9 production by Kupffer cells links the innate and adaptive immune response, providing a potential novel immunotherapeutic target in this common viral infection.

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) mediates natural killer cell suppression in chronic hepatitis B

BACKGROUND & AIMS

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) has been shown to influence autoimmune diseases; however, its function in viral infection has not been well-defined. We therefore investigated the expression and regulatory function of Tim-3 in natural killer (NK) cells in chronic Hepatitis B (CHB) infection.

METHODS

Seventy-six CHB patients, 38 healthy controls, and 18 patients with fatty liver disease (FLD) were tested for Tim-3 expression on peripheral blood mononuclear cells (PBMCs) and in the liver tissue by flow cytometry and immunohistochemical stainning. The effects of HBV infection on Tim-3 expression in NK cells and the roles of Tim-3 in regulation of NK-cell function were also studied.

RESULTS

There was a significant increase of Tim-3 expression in PBMCs, circulating NK cells and liver infiltrating lymphocytes (LILs) from CHB patients compared to that of healthy controls and FLD patients. Increased Tim-3 expression was also detected in NK92 cells that had been transfected with a HBV expression vector and NK cells isolated from the liver of HBV transgenic mice. Importantly, blockage of Tim-3 signaling with anti-Tim-3 antibodies or Tim-3-Fc fusion proteins resulted in an increased cytotoxicity for NK92 cells compared to HepG2 and HepG2.2.15 cells, as well as an elevated interferon-gamma (IFN-gamma) production. Similarly, enhanced cytotoxicity was also observed in PBMCs or NK cells from CHB patients treated with the Tim-3 blockade ex vivo.

CONCLUSION

HBV infection can up-regulate Tim-3 expression in NK cells, which may in turn suppress NK-cell functions in CHB patients.

Costimulation of Th17 cells: Adding fuel or putting out the fire in the inflamed gut?

Inflammatory bowel disease, typified by Crohn's disease and ulcerative colitis, is a common disorder characterized by recurrent and serious inflammation of the gastrointestinal tract. It is well documented that T cells play a pivotal role in the development of inflammatory bowel disease. Th17 cells are a unique T cell subpopulation implicated in inflammatory bowel disease and many other autoimmune/inflammatory diseases. However, the regulatory mechanism of Th17 activation and proliferation has not been defined completely. Recent studies have shown that the ligation of several costimulatory receptor-ligand pairs contributes to the activation, differentiation, and proliferation of T lymphocytes including the Th17 subset. In this review, we will discuss the emerging evidence on the role of Th17 cells in inflammatory bowel disease pathogenesis as well as the effect of costimulatory molecules on Th17 development and consider if the need for such costimulation of T lymphocytes provides a target for the development of novel therapeutic strategy.

Galectin-9 expands immunosuppressive macrophages to ameliorate T-cell-mediated lung inflammation

Galectin-9 (Gal-9) plays pivotal roles in the modulation of innate and adaptive immunity to suppress T-cell-mediated autoimmune models. However, it remains unclear if Gal-9 plays a suppressive role for T-cell function in non-autoimmune disease models. We assessed the effects of Gal-9 on experimental hypersensitivity pneumonitis induced by Trichosporon asahii. When Gal-9 was given subcutaneously to C57BL/6 mice at the time of challenge with T. asahii, it significantly suppressed T. asahii-induced lung inflammation, as the levels of IL-1, IL-6, IFN-gamma, and IL-17 were significantly reduced in the BALF of Gal-9-treated mice. Moreover, co-culture of anti-CD3-stimulated CD4 T cells with BALF cells harvested from Gal-9-treated mice on day 1 resulted in diminished CD4 T-cell proliferation and decreased levels of IFN-gamma and IL-17. CD11b(+)Ly-6C(high)F4/80(+) BALF Mphi expanded by Gal-9 were responsible for the suppression. We further found in vitro that Gal-9, only in the presence of T. asahii, expands CD11b(+)Ly-6C(high)F4/80(+) cells from BM cells, and the cells suppress T-cell proliferation and IFN-gamma and IL-17 production. The present results indicate that Gal-9 expands immunosuppressive CD11b(+)Ly-6C(high) Mphi to ameliorate Th1/Th17 cell-mediated hypersensitivity pneumonitis.

TIM-3 and its regulatory role in immune responses

T cell immunoglobulin mucin-(TIM)-3 was first identified as a molecule specifically expressed on IFN-γ-secreting CD4(+) T helper 1 (Th1) and CD8(+) T cytotoxic (Tc1) cells in both mice and humans. TIM-3 acts as a negative regulator of Th1/Tc1 cell function by triggering cell death upon interaction with its ligand, galectin-9. This negative regulatory function of TIM-3 has now been expanded to include its involvement in establishing and/or maintaining a state of T cell dysfunction or "exhaustion" observed in chronic viral diseases. In addition, it is now appreciated that TIM-3 has other ligands and is expressed on other cell types, where it may function differently. Given that an increasing body of data support an important role for TIM-3 in both autoimmune and chronic inflammatory diseases in humans, deciphering the function of TIM-3 on different cell types during different immune conditions and how these can be regulated will be critical for harnessing the therapeutic potential of TIM-3 for the treatment of disease.

Galectin-9 significantly prolongs the survival of fully mismatched cardiac allografts in mice

BACKGROUND

The involvement of T-cell immunoglobulin mucin-3 (Tim-3) in the regulation of solid organ transplantation rejection is largely unknown. We used galectin-9 (Tim-3 ligand) to evaluate the effect and mechanisms of Tim-3/galectin-9 pathway in an allogeneic heart transplant model.

METHODS

The murine cardiac transplant model from BALB/c (H-2d) to C57BL/6 (H-2b) was built. The recipients were administered with galectin-9 for 7 days from day 1 or day 3 posttransplant. The complete cessation of cardiac contractility was defined as the observation endpoint. The effect of galectin-9 on cell proliferation was assessed by mixed lymphocyte reaction. Histology and immunohistochemistry were performed to estimate the severity of rejection. The phenotype and cytokine profile of lymphocytes were analyzed by flow cytometry.

RESULTS

In vitro, galectin-9 suppressed the proliferation of lymphocytes mixed lymphocyte reactions in a dose- and beta-galactoside-dependent manner. In vivo, galectin-9 treatment from day 1 to day 3 posttransplant achieved similar survival time of grafts (median survival time, 22.7+/-1.2 vs. 23.0+/-1.0 days). The prolonged survival time was associated with reduced infiltration of CD4 and CD8 lymphocytes in allografts. Furthermore, the intragraft transcriptional profiling in galectin-9-treated group showed reduction of IFN-gamma and IL-17 mRNA but elevation of Ebi-3 and galectin-9 mRNA. Flow cytometry analysis indicated that galectin-9 treatment reduced the ratio of T helper (Th) 1 and Th17 cells in the draining lymph nodes and peripheral blood.

CONCLUSIONS

A short-course administration of galectin-9 significantly prolonged the survival of fully allogeneic cardiac allografts, which was associated with the suppression of Th1 and Th17 immune responses.

Involvement of T cell Ig Mucin-3 (Tim-3) in the negative regulation of inflammatory bowel disease

Augmented intestinal T cells, especially CD4(+)T cells, are involved in the pathogenesis of inflammatory bowel disease (IBD). We used a murine 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-induced colitis model to investigate whether Tim-3, a negative regulator of CD4(+)T cells, is involved in the suppression of IBD. We found that blocking the Tim-3 signal pathway exacerbated TNBS-induced colitis, as shown by increased weight loss and aggravated tissue injury. Blockade of the Tim-3 pathway resulted in an increase in Tim-3(+)CD4T cells, a biased T effector cell response, and a decrease in Treg cells. It also resulted in an altered profile of co-stimulatory molecules expressed on lymphocytes, which partially explained the biased polarization of different T cell subsets. Our data suggest that the Tim-3 pathway is highly involved in the negative regulation of IBD. A better understanding of this pathway may shed new light on the pathogenesis of this disease.

Galectin-9 ameliorates immune complex-induced arthritis by regulating Fc gamma R expression on macrophages

Galectin-9 up-regulated Fc gamma RIIb expression of mouse peritoneal macrophages in vitro but down-regulated Fc gamma RIII expression. Galectin-9-treated macrophages stimulated with immune complexes (IC) produced less TNFalpha and IL-1 beta but more IL-10 than PBS-treated macrophages. Macrophage enhancing effects on IC-induced C5a and neutrophil chemotactic activity were also diminished for galectin-9-treated macrophages. In galectin-9-treated mice, the severity of IC-induced arthritis was reduced, as were pro-inflammatory cytokine levels in inflamed joints and serum C5a. Fc gamma RIIb expression of macrophages from galectin-9-treated mice was up-regulated, whereas Fc gamma RIII expression was down-regulated. Macrophages from galectin-9-treated mice produced less TNFalpha and IL-1 beta but more IL-10 than PBS-treated mice. Disease severity of galectin-9-transgenic mice was milder than wild-type mice, whereas that of galectin-9-deficient mice was exaggerated. Furthermore, macrophage Fc gamma RIIb expression in galectin-9-deficient mice was down-regulated, while Fc gamma RIII expression was up-regulated. These results suggest that galectin-9 suppresses IC-induced inflammation partly by regulating Fc gamma R expression on macrophages.

Galectin-9 is a high affinity IgE-binding lectin with anti-allergic effect by blocking IgE-antigen complex formation

Galectin (Gal)-9 was first described as an eosinophil chemoattractant. With the progress in research, Gal-9 has come to be known as a versatile immunomodulator that is involved in various aspects of immune regulations, and the entire picture of the function still remains elusive. To uncover as-yet unknown activity of Gal-9, we have been examining the effect of the protein in various disease animal models. Here we show that Gal-9 attenuated asthmatic reaction in guinea pigs and suppressed passive-cutaneous anaphylaxis in mice. These results indicate the mast cell stabilizing effect of Gal-9. In vitro studies of mast cell degranulation involving RBL-2H3 cells demonstrated that Gal-9 suppressed degranulation from the cells stimulated by IgE plus antigen and that the inhibitory effect was completely abrogated in the presence of lactose, indicating lectin activity of Gal-9 is critical. We found that Gal-9 strongly and specifically bound IgE, which is a heavily glycosylated immunoglobulin, and that the interaction prevented IgE-antigen complex formation, clarifying the mode of action of the anti-degranulation effect. Gal-9 is expressed by several mast cells including mouse mast cell line MC/9. The fact that immunological stimuli of MC/9 cells augmented Gal-9 secretion from the cells implies that Gal-9 is an autocrine regulator of mast cell function to suppress excessive degranulation. Collectively, these findings shed light on a novel function of Gal-9 in mast cells and suggest a beneficial utility of Gal-9 for the treatment of allergic disorders including asthma.

Galectin-9 is a high affinity IgE-binding lectin with anti-allergic effect by blocking IgE-antigen complex formation

Galectin (Gal)-9 was first described as an eosinophil chemoattractant. With the progress in research, Gal-9 has come to be known as a versatile immunomodulator that is involved in various aspects of immune regulations, and the entire picture of the function still remains elusive. To uncover as-yet unknown activity of Gal-9, we have been examining the effect of the protein in various disease animal models. Here we show that Gal-9 attenuated asthmatic reaction in guinea pigs and suppressed passive-cutaneous anaphylaxis in mice. These results indicate the mast cell stabilizing effect of Gal-9. In vitro studies of mast cell degranulation involving RBL-2H3 cells demonstrated that Gal-9 suppressed degranulation from the cells stimulated by IgE plus antigen and that the inhibitory effect was completely abrogated in the presence of lactose, indicating lectin activity of Gal-9 is critical. We found that Gal-9 strongly and specifically bound IgE, which is a heavily glycosylated immunoglobulin, and that the interaction prevented IgE-antigen complex formation, clarifying the mode of action of the anti-degranulation effect. Gal-9 is expressed by several mast cells including mouse mast cell line MC/9. The fact that immunological stimuli of MC/9 cells augmented Gal-9 secretion from the cells implies that Gal-9 is an autocrine regulator of mast cell function to suppress excessive degranulation. Collectively, these findings shed light on a novel function of Gal-9 in mast cells and suggest a beneficial utility of Gal-9 for the treatment of allergic disorders including asthma.

Attenuation of Th1 response through galectin-9 and T-cell Ig mucin 3 interaction inhibits autoimmune diabetes in NOD mice

Galectin-9 (gal-9), widely expressed in many tissues, regulates Th1 cells and induces their apoptosis through its receptor, T-cell Ig mucin 3, which is mainly expressed on terminally differentiated Th1 cells. Type 1 diabetes is a Th1-dominant autoimmune disease that specifically destroys insulin-producing beta cells. To suppress the Th1 immune response in the development of autoimmune diabetes, we overexpressed gal-9 in NOD mice by injection of a plasmid encoding gal-9. Mice treated with gal-9 plasmid were significantly protected from diabetes and showed less severe insulitis compared with controls. Flow cytometric analyses in NOD-T1/2 double transgenic mice showed that Th1-cell population in spleen, pancreatic lymph node and pancreas was markedly decreased in gal-9 plasmid-treated mice, indicating a negative regulatory role of gal-9 in the development of pathogenic Th1 cells. Splenocytes from gal-9 plasmid-treated mice were less responsive to mitogenic stimulation than splenocytes from the control group. However, adoptive transfer of splenocytes from gal-9-treated or control mice caused diabetes in NOD/SCID recipients with similar kinetics, suggesting that gal-9 treatment does not induce active tolerance in NOD mice. We conclude that gal-9 may downregulate Th1 immune response in NOD mice and could be used as a therapeutic target in autoimmune diabetes.

Galectin 3 induces a distinctive pattern of cytokine and chemokine production in rheumatoid synovial fibroblasts via selective signaling pathways

OBJECTIVE

High expression of galectin 3 at sites of joint destruction in rheumatoid arthritis (RA) suggests that galectin 3 plays a role in RA pathogenesis. Previous studies have demonstrated the effects of galectins on immune cells, such as lymphocytes and macrophages. This study was undertaken to investigate the hypothesis that galectin 3 induces proinflammatory effects in RA by modulating the pattern of cytokine and chemokine production in synovial fibroblasts.

METHODS

Matched samples of RA synovial and skin fibroblasts were pretreated with galectin 3 or tumor necrosis factor alpha (TNFalpha), and the levels of a panel of cytokines, chemokines, and matrix metalloproteinases (MMPs) were determined using enzyme-linked immunosorbent assays and multiplex assays. Specific inhibitors were used to dissect signaling pathways, which were confirmed by Western blotting and NF-kappaB activation assay.

RESULTS

Galectin 3 induced secretion of interleukin-6 (IL-6), granulocyte-macrophage colony-stimulating factor, CXCL8, and MMP-3 in both synovial and skin fibroblasts. By contrast, galectin 3-induced secretion of TNFalpha, CCL2, CCL3, and CCL5 was significantly greater in synovial fibroblasts than in skin fibroblasts. TNFalpha blockade ruled out autocrine TNFalpha-stimulated induction of chemokines. The MAPKs p38, JNK, and ERK were necessary for IL-6 production, but phosphatidylinositol 3-kinase (PI 3-kinase) was required for selective CCL5 induction. NF-kappaB activation was required for production of both IL-6 and CCL5.

CONCLUSION

Our findings indicate that galectin 3 promotes proinflammatory cytokine secretion by tissue fibroblasts. However, galectin 3 induces the production of mononuclear cell-recruiting chemokines uniquely from synovial fibroblasts, but not matched skin fibroblasts, via a PI 3-kinase signaling pathway. These data provide further evidence of the role of synovial fibroblasts in regulating the pattern and persistence of the inflammatory infiltrate in RA and suggest a new and important functional consequence of the observed high expression of galectin 3 in the rheumatoid synovium.

The costimulatory role of TIM molecules

SUMMARY

The T-cell immunoglobulin domain and mucin domain (TIM) family, including TIM-1, TIM-2, TIM-3, and TIM-4, is a relatively newly described group of molecules with a conserved structure and important immunological functions, including T-cell activation, induction of T-cell apoptosis and T-cell tolerance, and the clearance of apoptotic cells. TIM-1 costimulates T-cell activation and enhances cytokine production. In humans, TIM-1 also serves as a susceptibility gene for allergy and asthma. TIM-3, expressed on T cells and dendritic cells, regulates T-cell apoptosis and immune tolerance. By contrast, TIM-4, which is expressed primarily on antigen-presenting cells and which is a receptor for phosphatidylserine, regulates T-cell activation and tolerance, in part by mediating the uptake and engulfment of apoptotic cells. The TIM molecules thus have surprisingly broad activities affecting multiple aspects of immunology.

Turning 'sweet' on immunity: galectin-glycan interactions in immune tolerance and inflammation

The function of deciphering the biological information encoded by the glycome, which is the entire repertoire of complex sugar structures expressed by cells and tissues, is assigned in part to endogenous glycan-binding proteins or lectins. Galectins, a family of animal lectins that bind N-acetyllactosamine-containing glycans, have many roles in diverse immune cell processes, including those relevant to pathogen recognition, shaping the course of adaptive immune responses and fine-tuning the inflammatory response. How do galectins translate glycan-encoded information into tolerogenic or inflammatory cell programmes? An improved understanding of the mechanisms underlying these functions will provide further opportunities for developing new therapies based on the immunoregulatory properties of this multifaceted protein family.