LIGHT Is Constitutively Expressed on T and NK Cells in the Human Gut and Can Be Induced by CD2-Mediated Signaling

Multilayered Computational Framework for Designing Peptide Inhibitors of HVEM-LIGHT Interaction

The herpesvirus entry mediator (HVEM) and its ligand LIGHT play crucial roles in immune system regulation, including T-cell proliferation, B-cell differentiation, and immunoglobulin secretion. However, excessive T-cell activation can lead to chronic inflammation and autoimmune diseases. Thus, inhibiting the HVEM-LIGHT interaction emerges as a promising therapeutic strategy for these conditions and in preventing adverse reactions in organ transplantation. This study focused on designing peptide inhibitors, targeting the HVEM-LIGHT interaction, using molecular dynamics (MD) simulations of 65 peptides derived from HVEM. These peptides varied in length and disulfide-bond configurations, crucial for their interaction with the LIGHT trimer. By simulating 31 HVEM domain variants, including the full-length protein, we assessed conformational changes upon LIGHT binding to understand the influence of HVEM segments and disulfide bonds on the binding mechanism. Employing multitrajectory microsecond-scale, all-atom MD simulations and molecular mechanics with generalized Born and surface area (MM-GBSA) binding energy estimation, we identified promising CRD2 domain variants with high LIGHT affinity. Notably, point mutations in these variants led to a peptide with a single disulfide bond (C58-C73) and a K54E substitution, exhibiting the highest binding affinity. The importance of the CRD2 domain and Cys58-Cys73 disulfide bond for interrupting HVEM-LIGHT interaction was further supported by analyzing truncated CRD2 variants, demonstrating similar binding strengths and mechanisms. Further investigations into the binding mechanism utilized steered MD simulations at various pulling speeds and umbrella sampling to estimate the energy profile of HVEM-based inhibitors with LIGHT. These comprehensive analyses revealed key interactions and different binding mechanisms, highlighting the increased binding affinity of selected peptide variants. Experimental circular dichroism techniques confirmed the structural properties of these variants. This study not only advances our understanding of the molecular basis of HVEM-LIGHT interactions but also provides a foundation for developing novel therapeutic strategies for immune-related disorders. Furthermore, it sets a gold standard for peptide inhibitor design in drug development due to its systematic approach.

LIGHT Amplification by NF-κB Contributes to TLR3 Signaling Pathway-Induced Acute Hepatitis

LIGHT is a member of the TNF superfamily and a proinflammatory cytokine involved in liver pathogenesis. Many liver diseases involve activation of Toll-like receptor 3 (TLR3), which is activated by double-stranded RNA (dsRNA). However, the involvement of LIGHT in TLR3 implicated liver diseases is not clear. In this study, we investigated the role of LIGHT in TLR3 involved liver pathogenesis by using a mouse model of TLR3 agonist poly(I:C)-induced hepatitis. We found LIGHT expression at both protein and mRNA level in liver tissues is dramatically increased during the course of poly(I:C)-induced liver injury. This induction depends on NF-κB activation as pretreating the mice with a NF-κB inhibitor abrogates LIGHT upregulation. Importantly, blockade of the LIGHT signaling pathway with the recombinant LIGHT receptor HVEM protein ameliorates liver injury in poly(I:C)-induced hepatitis. Conclusions. These results indicate that LIGHT amplification by NF-κB plays a significant role in TLR3 involved hepatitis and points LIGHT to be a potential drug target for liver disease therapy.

Realigning the LIGHT signaling network to control dysregulated inflammation

Advances in understanding the physiologic functions of the tumor necrosis factor superfamily (TNFSF) of ligands, receptors, and signaling networks are providing deeper insight into pathogenesis of infectious and autoimmune diseases and cancer. LIGHT (TNFSF14) has emerged as an important modulator of critical innate and adaptive immune responses. LIGHT and its signaling receptors, herpesvirus entry mediator (TNFRSF14), and lymphotoxin β receptor, form an immune regulatory network with two co-receptors of herpesvirus entry mediator, checkpoint inhibitor B and T lymphocyte attenuator, and CD160. Deciphering the fundamental features of this network reveals new understanding to guide therapeutic development. Accumulating evidence from infectious diseases points to the dysregulation of the LIGHT network as a disease-driving mechanism in autoimmune and inflammatory reactions in barrier organs, including coronavirus disease 2019 pneumonia and inflammatory bowel diseases. Recent clinical results warrant further investigation of the LIGHT regulatory network and application of target-modifying therapeutics for disease intervention.

An epithelial Nfkb2 pathway exacerbates intestinal inflammation by supplementing latent RelA dimers to the canonical NF-κB module

Aberrant inflammation, such as that associated with inflammatory bowel disease (IBD), is fueled by the inordinate activity of RelA/NF-κB factors. As such, the canonical NF-κB module mediates controlled nuclear activation of RelA dimers from the latent cytoplasmic complexes. What provokes pathological RelA activity in the colitogenic gut remains unclear. The noncanonical NF-κB pathway typically promotes immune organogenesis involving Nfkb2 gene products. Because NF-κB pathways are intertwined, we asked whether noncanonical signaling aggravated inflammatory RelA activity. Our investigation revealed frequent engagement of the noncanonical pathway in human IBD. In a mouse model of experimental colitis, we established that Nfkb2-mediated regulations escalated the RelA-driven proinflammatory gene response in intestinal epithelial cells, exacerbating the infiltration of inflammatory cells and colon pathologies. Our mechanistic studies clarified that cell-autonomous Nfkb2 signaling supplemented latent NF-κB dimers, leading to a hyperactive canonical RelA response in the inflamed colon. In sum, the regulation of latent NF-κB dimers appears to link noncanonical Nfkb2 signaling to RelA-driven inflammatory pathologies and may provide for therapeutic targets.

Soluble ligands as drug targets for treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is characterized by persistent inflammation in a hereditarily susceptible host. In addition to gastrointestinal symptoms, patients with IBD frequently suffer from extra-intestinal complications such as fibrosis, stenosis or cancer. Mounting evidence supports the targeting of cytokines for effective treatment of IBD. Cytokines can be included in a newly proposed classification "soluble ligands" that has become the third major target of human protein therapeutic drugs after enzymes and receptors. Soluble ligands have potential significance for research and development of anti-IBD drugs. Compared with traditional drug targets for IBD treatment, such as receptors, at least three factors contribute to the increasing importance of soluble ligands as drug targets. Firstly, cytokines are the main soluble ligands and targeting of them has demonstrated efficacy in patients with IBD. Secondly, soluble ligands are more accessible than receptors, which are embedded in the cell membrane and have complex tertiary membrane structures. Lastly, certain potential target proteins that are present in membrane-bound forms can become soluble following cleavage, providing further opportunities for intervention in the treatment of IBD. In this review, 49 drugs targeting 25 distinct ligands have been evaluated, including consideration of the characteristics of the ligands and drugs in respect of IBD treatment. In addition to approved drugs targeting soluble ligands, we have also assessed drugs that are in preclinical research and drugs inhibiting ligand-receptor binding. Some new types of targetable soluble ligands/proteins, such as epoxide hydrolase and p-selectin glycoprotein ligand-1, are also introduced. Targeting soluble ligands not only opens a new field of anti-IBD drug development, but the circulating soluble ligands also provide diagnostic insights for early prediction of treatment response. In conclusion, soluble ligands serve as the third-largest protein target class in medicine, with much potential for the drugs targeting them.

Increased Production of LIGHT by T Cells in Eosinophilic Esophagitis Promotes Differentiation of Esophageal Fibroblasts Toward an Inflammatory Phenotype

BACKGROUND & AIMS

Eosinophilic esophagitis (EoE) is an antigen-mediated eosinophilic disease of the esophagus that involves fibroblast activation and progression to fibrostenosis. Cytokines produced by T-helper type 2 cells and transforming growth factor beta 1 (TGFβ1) contribute to the development of EoE, but other cytokines involved in pathogenesis are unknown. We investigate the effects of tumor necrosis factor superfamily member 14 (TNFSF14, also called LIGHT) on fibroblasts in EoE.

METHODS

We analyzed publicly available esophageal CD3+ T-cell single-cell sequencing data for expression of LIGHT. Esophageal tissues were obtained from pediatric patients with EoE or control individuals and analyzed by immunostaining. Human primary esophageal fibroblasts were isolated from esophageal biopsy samples of healthy donors or patients with active EoE. Fibroblasts were cultured; incubated with TGFβ1 and/or LIGHT; and analyzed by RNA sequencing, flow cytometry, immunoblots, immunofluorescence, or reverse transcription polymerase chain reaction. Eosinophils were purified from peripheral blood of healthy donors, incubated with interleukin 5, cocultured with fibroblasts, and analyzed by immunohistochemistry.

RESULTS

LIGHT was up-regulated in the esophageal tissues from patients with EoE, compared with control individuals, and expressed by several T-cell populations, including T-helper type 2 cells. TNF receptor superfamily member 14 (TNFRSF14, also called HVEM) and lymphotoxin beta receptor are receptors for LIGHT that were expressed by fibroblasts from healthy donors or patients with active EoE. Stimulation of esophageal fibroblasts with LIGHT induced inflammatory gene transcription, whereas stimulation with TGFβ1 induced transcription of genes associated with a myofibroblast phenotype. Stimulation of fibroblasts with TGFβ1 increased expression of HVEM; subsequent stimulation with LIGHT resulted in their differentiation into cells that express markers of myofibroblasts and inflammatory chemokines and cytokines. Eosinophils tethered to esophageal fibroblasts after LIGHT stimulation via intercellular adhesion molecule-1.

CONCLUSIONS

T cells in esophageal tissues from patients with EoE express increased levels of LIGHT compared with control individuals, which induces differentiation of fibroblasts into cells with inflammatory characteristics. TGFβ1 increases fibroblast expression of HVEM, a receptor for LIGHT. LIGHT mediates interactions between esophageal fibroblasts and eosinophils via ICAM1. This pathway might be targeted for the treatment of EoE.

Systemic Inflammatory Protein Profiles Distinguish Irritable Bowel Syndrome (IBS) and Ulcerative Colitis, Irrespective of Inflammation or IBS-Like Symptoms

BACKGROUND

Inflammatory mechanisms of ulcerative colitis (UC) and irritable bowel syndrome (IBS) may overlap or are part of different spectrums. However, potential links between inflammation and IBS-like symptoms in these patient groups are still unclear. The aim of this study was to determine if the systemic inflammatory protein (SIP) profiles differ between UC patients, with presence of inflammation or in remission with or without IBS-like symptoms, and IBS patients.

METHODS

Serum from patients with active UC (UCA), UC patients in remission with or without IBS-like symptoms (UCR + IBS, UCR-IBS), IBS patients (IBS), and healthy subjects (HS) was analyzed using the ProSeek Multiplex Inflammation kit, which detects 92 proteins.

RESULTS

The exploratory cohort consisted of 166 subjects (UCA, n = 40; UCR-IBS, n = 45; UCR + IBS, n = 20; IBS, n = 40; HS, n = 21). Systemic inflammatory protein profiles separated UC from non-UC (HS and IBS) patients in multivariate analysis, revealing caspase 8, axin 1, sulfotransferase 1A1, and tumor necrosis factor superfamily member 14 as the variables most important to clustering. Although minor differences were detected between UCR + IBS and UCR-IBS, SIP profiles discriminated UCA from UCR, and interleukin (IL) 17C, IL17A, chemokine ligand 9, and transforming growth factor-α characterized active inflammation. SIP profiles weakly discriminated HS from IBS, although fibroblast growth factor 21 and IL6 serum levels were higher in IBS. Results were confirmed in a validation cohort (UCA, n = 15; UCR + IBS, n = 9; IBS, n = 14).

CONCLUSIONS

SIP profiles distinguish UC patients from IBS patients, irrespective of inflammation or IBS-like symptoms, suggesting that inflammatory mechanisms of the diseases are part of different spectrums.

Soluble Fc-Disabled Herpes Virus Entry Mediator Augments Activation and Cytotoxicity of NK Cells by Promoting Cross-Talk between NK Cells and Monocytes

CD160 is highly expressed by NK cells and is associated with cytolytic effector activity. Herpes virus entry mediator (HVEM) activates NK cells for cytokine production and cytolytic function via CD160. Fc-fusions are a well-established class of therapeutics, where the Fc domain provides additional biological and pharmacological properties to the fusion protein including enhanced serum t 1/2 and interaction with Fc receptor-expressing immune cells. We evaluated the specific function of HVEM in regulating CD160-mediated NK cell effector function by generating a fusion of the HVEM extracellular domain with human IgG1 Fc bearing CD16-binding mutations (Fc*) resulting in HVEM-(Fc*). HVEM-(Fc*) displayed reduced binding to the Fc receptor CD16 (i.e., Fc-disabled HVEM), which limited Fc receptor-induced responses. HVEM-(Fc*) functional activity was compared with HVEM-Fc containing the wild type human IgG1 Fc. HVEM-(Fc*) treatment of NK cells and PBMCs caused greater IFN-γ production, enhanced cytotoxicity, reduced NK fratricide, and no change in CD16 expression on human NK cells compared with HVEM-Fc. HVEM-(Fc*) treatment of monocytes or PBMCs enhanced the expression level of CD80, CD83, and CD40 expression on monocytes. HVEM-(Fc*)-enhanced NK cell activation and cytotoxicity were promoted via cross-talk between NK cells and monocytes that was driven by cell-cell contact. In this study, we have shown that soluble Fc-disabled HVEM-(Fc*) augments NK cell activation, IFN-γ production, and cytotoxicity of NK cells without inducing NK cell fratricide by promoting cross-talk between NK cells and monocytes without Fc receptor-induced effects. Soluble Fc-disabled HVEM-(Fc*) may be considered as a research and potentially therapeutic reagent for modulating immune responses via sole activation of HVEM receptors.

Reverse Signaling of Tumor Necrosis Factor Superfamily Proteins in Macrophages and Microglia: Superfamily Portrait in the Neuroimmune Interface

The tumor necrosis factor (TNF) superfamily (TNFSF) is a protein superfamily of type II transmembrane proteins commonly containing the TNF homology domain. The superfamily contains more than 20 protein members, which can be released from the cell membrane by proteolytic cleavage. Members of the TNFSF function as cytokines and regulate diverse biological processes, including immune responses, proliferation, differentiation, apoptosis, and embryogenesis, by binding to TNFSF receptors. Many TNFSF proteins are also known to be responsible for the regulation of innate immunity and inflammation. Both receptor-mediated forward signaling and ligand-mediated reverse signaling play important roles in these processes. In this review, we discuss the functional expression and roles of various reverse signaling molecules and pathways of TNFSF members in macrophages and microglia in the central nervous system (CNS). A thorough understanding of the roles of TNFSF ligands and receptors in the activation of macrophages and microglia may improve the treatment of inflammatory diseases in the brain and periphery. In particular, TNFSF reverse signaling in microglia can be exploited to gain further insights into the functions of the neuroimmune interface in physiological and pathological processes in the CNS.

The atopic dermatitis blood signature is characterized by increases in inflammatory and cardiovascular risk proteins

Beyond classic “allergic”/atopic comorbidities, atopic dermatitis (AD) emerges as systemic disease with increased cardiovascular risk. To better define serum inflammatory and cardiovascular risk proteins, we used an OLINK high-throughput proteomic assay to analyze moderate-to-severe AD (n = 59) compared to psoriasis (n = 22) and healthy controls (n = 18). Compared to controls, 10 proteins were increased in serum of both diseases, including Th1 (IFN-γ, CXCL9, TNF-β) and Th17 (CCL20) markers. 48 proteins each were uniquely upregulated in AD and psoriasis. Consistent with skin expression, AD serum showed up-regulation of Th2 (IL-13, CCL17, eotaxin-1/CCL11, CCL13, CCL4, IL-10), Th1 (CXCL10, CXCL11) and Th1/Th17/Th22 (IL-12/IL-23p40) responses. Surprisingly, some markers of atherosclerosis (fractalkine/CX3CL1, CCL8, M-CSF, HGF), T-cell development/activation (CD40L, IL-7, CCL25, IL-2RB, IL-15RA, CD6) and angiogenesis (VEGF-A) were significantly increased only in AD. Multiple inflammatory pathways showed stronger enrichment in AD than psoriasis. Several atherosclerosis mediators in serum (e.g. E-selectin, PI3/elafin, CCL7, IL-16) correlated with SCORAD, but not BMI. Also, AD inflammatory mediators (e.g. MMP12, IL-12/IL-23p40, CXCL9, CCL22, PI3/Elafin) correlated between blood and lesional as well as non-lesional skin. Overall, the AD blood signature was largely different compared to psoriasis, with dysregulation of inflammatory and cardiovascular risk markers, strongly supporting its systemic nature beyond atopic/allergic association.

The Role of Cytokines in the Fibrotic Responses in Crohn's Disease

Crohn’s disease is an idiopathic disorder of the gut thought to be caused by a combination of environmental and genetic factors in susceptible individuals. It is characterized by chronic transmural inflammation of the terminal ileum and colon, with typical transmural lesions. Complications, including fibrosis, mean that between 40 and 70% of patients require surgery in the first 10 years after diagnosis. Presently, there is no evidence that the current therapies which dampen inflammation modulate or reverse intestinal fibrosis. In this review, we focus on cytokines that may lead to fibrosis and stenosis and the contribution of experimental models for understanding and treatment of gut fibrosis.

Immunoregulation of Inflammatory and Inhibitory Cytokines by Vitamin D3 in Patients with Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD) is a group of idiopathic, chronic and relapsing inflammatory conditions of the gastrointestinal tract, caused by an aberrant and exaggerated immunological response in the gut. Supplementation of vitamin D3 in patients with IBD exerts both direct and indirect regulatory roles on the naïve T cells, thereby maintaining a balance between inflammatory and inhibitory cytokines. The direct actions of vitamin D3 on naïve T cells result in the proliferation of more regulatory T cells and inhibitory cytokines such as IL-4, IL-10 and IL-5. The binding of vitamin D to dendritic cells (DCs) through vitamin D receptors inhibits the action of IL-12 on DCs, resulting in the downregulation of Th1 and Th17. On the other hand, this interaction favours Th2 and Treg upregulation and facilitates the maintenance of immune homoeostasis between inflammatory and inhibitory cytokines which is essentially significant in the management of patients with IBD. The aim of this review was to explore the current and mounting scientific evidence on the roles of vitamin D3 in immunoregulation of inflammatory and inhibitory cytokines in patients with IBDs. An extensive literature search was conducted using keywords such as Vitamin D3*, IBD*, inflammatory cytokines*, inhibitory cytokines*, naïve-T-cells* and antigen presenting cells* through PubMed, SCOPUS and MEDLINE search engines. The results of the accumulated bodies of research that have been conducted demonstrate that vitamin D3 plays a major role not only in the immunoregulation of cytokines involved in the pathogenesis of IBDs but also in many other inflammatory disorders.

Molecular pathways driving disease-specific alterations of intestinal epithelial cells

Due to the fact that chronic inflammation as well as tumorigenesis in the gut is crucially impacted by the fate of intestinal epithelial cells, our article provides a comprehensive overview of the composition, function, regulation and homeostasis of the gut epithelium. In particular, we focus on those aspects which were found to be altered in the context of inflammatory bowel diseases or colorectal cancer and also discuss potential molecular targets for a disease-specific therapeutic intervention.

A Randomized Phase 1 Study to Assess the Safety and Pharmacokinetics of the Subcutaneously Injected Anti-LIGHT Antibody, SAR252067

LIGHT, a member of the tumor necrosis factor superfamily, is potentially involved in mucosal inflammation associated with inflammatory bowel disease. The safety and pharmacokinetics of the fully human monoclonal anti-LIGHT antibody, SAR252067, was evaluated in healthy volunteers in a phase 1 study as a potential treatment for diseases related to LIGHT-mediated mucosal inflammation. This double-blind, randomized, placebo-controlled, sequential ascending single-dose, single-center, 16-week study randomized 48 subjects to a single subcutaneous dose of SAR252067 (40, 120, 300, 600, 900, or 1200 mg) or placebo. Safety assessments included adverse events (AEs), injection-site reactions, and antidrug antibody (ADA) titer. Pharmacokinetic end points were serum parameters of SAR252067 (C_max , AUC_0-∞ , t_max , t_1/2z ). Serum-soluble LIGHT concentrations were also determined. Safety analyses included all 48 participants; pharmacokinetic analyses included 36 subjects who received SAR252067. No serious AEs were reported, and no dose-effect relationship was apparent. Injection-site reactions were minimal. ADAs were not clinically relevant. SAR252067 exposure increased in a near-dose-proportional manner, median t_max ranged from 5.0 to 8.5 days, and t_1/2z ranged from 18.0 to 27.0 days. Serum-soluble LIGHT significantly increased after SAR252067 administration with the 40-mg dose only. SAR252067 had a good safety profile, was well tolerated in healthy humans, and displayed a predictable pharmacokinetic profile.

Context-dependent roles for lymphotoxin-β receptor signaling in cancer development

The LTα1β2 and LIGHT TNF superfamily cytokines exert pleiotropic physiological functions through the activation of their cognate lymphotoxin-β receptor (LTβR). Interestingly, since the discovery of these proteins, accumulating evidence has pinpointed a role for LTβR signaling in carcinogenesis. Early studies have shown a potential anti-tumoral role in a subset of solid cancers either by triggering apoptosis in malignant cells or by eliciting an anti-tumor immune response. However, more recent studies provided robust evidence that LTβR signaling is also involved in diverse cell-intrinsic and microenvironment-dependent pro-oncogenic mechanisms, affecting several solid and hematological malignancies. Consequently, the usefulness of LTβR signaling axis blockade has been investigated as a potential therapeutic approach for cancer. Considering the seemingly opposite roles of LTβR signaling in diverse cancer types and their key implications for therapy, we here extensively review the different mechanisms by which LTβR activation affects carcinogenesis, focusing on the diverse contexts and different models assessed.

Therapeutic blockade of LIGHT interaction with herpesvirus entry mediator and lymphotoxin β receptor attenuates in vivo cytotoxic allogeneic responses

BACKGROUND

Tumor necrosis factor/tumor necrosis factor receptor superfamily members conform a group of molecular interaction pathways of essential relevance during the process of T-cell activation and differentiation toward effector cells and particularly for the maintenance phase of the immune response. Specific blockade of these interacting pathways, such as CD40-CD40L, contributes to modulate the deleterious outcome of allogeneic immune responses. We postulated that antagonizing the interaction of LIGHT expression on activated T cells with its receptors, herpesvirus entry mediator and lymphotoxin β receptor, may decrease T cell-mediated allogeneic responses.

METHODS

A flow cytometry competition assay was designed to identify anti-LIGHT monoclonal antibodies capable to prevent the interaction of mouse LIGHT with its receptors expressed on transfected cells. An antibody with the desired specificity was evaluated in a short-term in vivo allogeneic cytotoxic assay and tested for its ability to detect endogenous mouse LIGHT.

RESULTS

We provide evidence for the first time that in mice, as previously described in humans, LIGHT protein is rapidly and transiently expressed after T-cell activation, and this expression was stronger on CD8 T cells than on CD4 T cells. Two anti-LIGHT antibodies prevented interactions of mouse LIGHT with its two known receptors, herpesvirus entry mediator and lymphotoxin β receptor. In vivo administration of anti-LIGHT antibody (clone 10F12) ameliorated host antidonor short-term cytotoxic response in wild type B6 mice, although to a lesser extent than that observed in LIGHT-deficient mice.

CONCLUSION

The therapeutic targeting of LIGHT may contribute to achieve a better control of cytotoxic responses refractory to current immunosuppressive drugs in transplantation.

Licensed human natural killer cells aid dendritic cell maturation via TNFSF14/LIGHT

Interactions between natural killer (NK) cells and dendritic cells (DCs) aid DC maturation and promote T-cell responses. Here, we have analyzed the response of human NK cells to tumor cells, and we identify a pathway by which NK-DC interactions occur. Gene expression profiling of tumor-responsive NK cells identified the very rapid induction of TNF superfamily member 14 [TNFSF14; also known as homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for HVEM, a receptor expressed by T lymphocytes (LIGHT)], a cytokine implicated in the enhancement of antitumor responses. TNFSF14 protein expression was induced by three primary mechanisms of NK cell activation, namely, via the engagement of CD16, by the synergistic activity of multiple target cell-sensing NK-cell activation receptors, and by the cytokines IL-2 and IL-15. For antitumor responses, TNFSF14 was preferentially produced by the licensed NK-cell population, defined by the expression of inhibitory receptors specific for self-MHC class I molecules. In contrast, IL-2 and IL-15 treatment induced TNFSF14 production by both licensed and unlicensed NK cells, reflecting the ability of proinflammatory conditions to override the licensing mechanism. Importantly, both tumor- and cytokine-activated NK cells induced DC maturation in a TNFSF14-dependent manner. The coupling of TNFSF14 production to tumor-sensing NK-cell activation receptors links the tumor immune surveillance function of NK cells to DC maturation and adaptive immunity. Furthermore, regulation by NK cell licensing helps to safeguard against TNFSF14 production in response to healthy tissues.

Tumour necrosis factor superfamily members in the pathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the gastrointestinal tract of unclear aetiology of which two major forms are Crohn's disease (CD) and ulcerative colitis (UC). CD and UC are immunologically distinct, although they both result from hyperactivation of proinflammatory pathways in intestines and disruption of intestinal epithelial barrier. Members of the tumour necrosis factor superfamily (TNFSF) are molecules of broad spectrum of activity, including direct disruption of intestinal epithelial barrier integrity and costimulation of proinflammatory functions of lymphocytes. Tumour necrosis factor (TNF) has a well-established pathological role in IBD which also serves as a target in IBD treatment. In this review we discuss the role of TNF and other TNFSF members, notably, TL1A, FasL, LIGHT, TRAIL, and TWEAK, in the pathogenesis of IBD.

Soluble Biomarkers Associated with Response to Treatment with Tumor Necrosis Factor Inhibitors in Psoriatic Arthritis

Objective.

To identify soluble biomarkers associated with response to therapy with tumor necrosis factor inhibitors (TNFi) in patients with psoriatic arthritis (PsA).

Methods.

The study was conducted at a PsA clinic where patients are assessed every 6 months, and serum samples are collected and stored once a year at the time of clinical assessment. Forty patients with active PsA who gave serum samples prior to treatment with TNFi and after at least 3 months of therapy were identified. Patients were classified as TNFi responders if tender joint count was < 3, swollen joint count was 0, and Psoriasis Area and Severity Index score was < 4 at the time the second sample was collected. The following biomarkers were tested by ELISA: TNF superfamily 14, matrix metalloprotease-3 (MMP-3), receptor activator of nuclear factor kappa-B ligand, osteoprotegerin, cartilage oligomeric matrix protein (COMP), CPII, C2C and C1-2C, CS-846, and highly sensitive C-reactive protein. Paired t tests and logistic regression was used for statistical analyses.

Results.

After a mean treatment duration of 11 months with TNFi (etanercept 28 patients, adalimumab 6, golimumab 4, infliximab 2), 29 patients were classified as TNFi responders. Baseline level of MMP-3 was independently associated with responder status (OR 1.067 for each 1-unit increase, p = 0.045). A reduction in MMP-3 levels with therapy increased the odds of achieving response (OR 1.213 for each 1-unit change, p = 0.030), whereas a reduction in COMP decreased the odds (OR 0.587, for each 100-unit increase, p = 0.039). None of the other biomarkers was associated with response.

Conclusion.

Baseline as well as reduction in serum MMP-3 and increase in serum COMP are independently associated with response to TNFi therapy in patients with PsA.

Clinical targeting of the TNF and TNFR superfamilies

Inhibitors of tumour necrosis factor (TNF) are among the most successful protein-based drugs (biologics) and have proven to be clinically efficacious at reducing inflammation associated with several autoimmune diseases. As a result, attention is focusing on the therapeutic potential of additional members of the TNF superfamily of structurally related cytokines. Many of these TNF-related cytokines or their cognate receptors are now in preclinical or clinical development as possible targets for modulating inflammatory diseases and cancer as well as other indications. This Review focuses on the biologics that are currently in clinical trials for immune-related diseases and other syndromes, discusses the successes and failures to date as well as the expanding therapeutic potential of modulating the activity of this superfamily of molecules.

Protein therapeutics targeted at the TNF superfamily

Protein-based drugs with their unequivocal specificity achieved the long sought milestone of selectively disrupting cytokine pathways to alleviate ongoing inflammation. Tumor necrosis factor (TNF), a member of the superfamily of cytokines involved in regulating immune and inflammatory processes, provides an exemplary model of protein therapeutics. Antibody and receptor-based inhibitors of TNF modify inflammation leading to dramatic improvement in patients with certain autoimmune diseases. Collectively, the structure, specificity and valence of these protein-based drugs provide direct evidence that the essential mechanism of action is antagonism of the ligand-receptor interaction. Accumulating clinical knowledge regarding TNF inhibitors also provide insights into the mechanisms involved in different autoimmune diseases. Experience in the development of an arsenal of biologics directed at TNF has additionally contributed to knowledge toward overcoming the challenges of protein drugs, which include production, delivery, antigenicity and pharmacodynamics. Dramatic clinical outcomes with TNF inhibitors are driving investigation and development of biologics toward other members of the TNF superfamily to selectively alter functional properties of the immune system.

Isolation and characterization of LIGHT (TNFSF14) gene homologue in zebrafish (Danio rerio)

The tumor necrosis factor superfamily (TNFSF) proteins are cytokines involved in many biological processes. In this study, the TNF superfamily member 14 (TNFSF14, LIGHT) has been isolated from zebrafish Danio rerio (designated zLIGHT). The full-length open reading frame (ORF) of zLIGHT cDNA consists of 708 bp encoding a protein of 235 amino acids. The zLIGHT open reading frame (ORF) genomic sequence consists of three introns and four exons, is about 9.9 kb in size. Real-time quantitative PCR (qPCR) analysis suggested that zLIGHT was predominantly expressed in zebrafish spleen. The soluble LIGHT (zsLIGHT) had been cloned into the pSUMO vector, SDS-PAGE and Western blotting analysis confirmed that the recombinant protein SUMO-zsLIGHT was efficiently expressed in Escherichia coli BL21 (DE3). Laser scanning confocal microscopy analysis showed that SUMO-zsLIGHT could bind to its receptors on T cells. LIGHT is involved in many important biological effects, including up-regulating proinflammatory chemokines, cytokines, inducing cell death, apoptosis, and enhancing T cell survival. Zebrafish may conduct as a model animal for further research on LIGHT.

The role of coinhibitory signaling pathways in transplantation and tolerance

Negative costimulatory molecules, acting through so-called inhibitory pathways, play a crucial role in the control of T cell responses. This negative “second signal” opposes T cell receptor activation and leads to downregulation of T cell proliferation and promotes antigen specific tolerance. Much interest has focused upon these pathways in recent years as a method to control detrimental alloresponses and promote allograft tolerance. However, recent experimental data highlights the complexity of negative costimulatory pathways in alloimmunity. Varying effects are observed from molecules expressed on donor and recipient tissues and also depending upon the activation status of immune cells involved. There appears to be significant overlap and redundancy within these systems, rendering this a challenging area to understand and exploit therapeutically. In this article, we will review the literature at the current time regarding the major negative costimulation pathways including CTLA-4:B7, PD-1:PD-L1/PD-L2 and PD-L1:B7-1, B7-H3, B7-H4, HVEM:BTLA/CD160, and TIM-3:Galectin-9. We aim to outline the role of these pathways in alloimmunity and discuss their potential applications for tolerance induction in transplantation.

The signaling networks of the herpesvirus entry mediator (TNFRSF14) in immune regulation

The tumor necrosis factor (TNF) receptor superfamily member herpesvirus entry mediator (HVEM) (TNFRSF14) regulates T-cell immune responses by activating both inflammatory and inhibitory signaling pathways. HVEM acts as both a receptor for the canonical TNF-related ligands, LIGHT [lymphotoxin-like, exhibits inducible expression, and competes with herpes simplex virus glycoprotein D for HVEM, a receptor expressed on T lymphocytes] and lymphotoxin-α, and as a ligand for the immunoglobulin superfamily proteins BTLA (B and T lymphocyte attenuator) and CD160, a feature distinguishing HVEM from other immune regulatory molecules. The ability of HVEM to interact with multiple ligands in distinct configurations creates a functionally diverse set of intrinsic and bidirectional signaling pathways that control both inflammatory and inhibitory responses. The HVEM system is integrated into the larger LTβR and TNFR network through extensive shared ligand and receptor usage. Experimental mouse models and human diseases indicate that dysregulation of HVEM network may contribute to autoimmune pathogenesis, making it an attractive target for drug intervention.

HVEM signalling promotes colitis

BACKGROUND

Tumor necrosis factor super family (TNFSF) members regulate important processes involved in cell proliferation, survival and differentiation and are therefore crucial for the balance between homeostasis and inflammatory responses. Several members of the TNFSF are closely associated with inflammatory bowel disease (IBD). Thus, they represent interesting new targets for therapeutic treatment of IBD.

METHODOLOGY/PRINCIPAL FINDINGS

We have used mice deficient in TNFSF member HVEM in experimental models of IBD to investigate its role in the disease process. Two models of IBD were employed: i) chemical-induced colitis primarily mediated by innate immune cells; and ii) colitis initiated by CD4(+)CD45RB(high) T cells following their transfer into immuno-deficient RAG1(-/-) hosts. In both models of disease the absence of HVEM resulted in a significant reduction in colitis and inflammatory cytokine production.

CONCLUSIONS

These data show that HVEM stimulatory signals promote experimental colitis driven by innate or adaptive immune cells.

CD161 DEFINES EFFECTOR T CELLS THAT EXPRESS LIGHT AND RESPOND TO TL1A-DR3 SIGNALING

Expression of NK cell markers identifies pro-inflammatory T cell subsets in the liver and intestinal immune compartments. Specifically, CD161 is expressed on Th17 cells which play an important role in the regulation of mucosal inflammation. In this study, we characterized human peripheral blood CD161+ T cells as an effector population partially resembling a gut T cell phenotype. CD161+ CD4+ T cells express the gut-associated TNF family member, LIGHT, and respond to crosslinking of DR3, a receptor to another gut-associated cytokine, TL1A. Robust IFN-γ production in response to DR3 signaling correlated with enhanced expression of surface DR3 on CD161+ T cells and co-stimulation with IL12 and IL18. CD161+ T cell effector function was directly demonstrated by activation of responder monocytes in co-culture leading to CD40 upregulation and CD14 downregulation. CD161+ T cells reciprocally responded to activated monocytes, inducing expression of activation marker, CD69, and production of IL2 and IFN-γ, further demonstrating effective CD161+ T cell cross-talk with monocytes. Finally, CD161 defined a subset of T cells that co-express CD56, a second NK marker. Our findings implicate human CD161+ T cells in gut-associated signaling mechanisms, and suggest a monocyte mediated effector function in mucosal inflammation.

LIGHT/TNFSF14 enhances adipose tissue inflammatory responses through its interaction with HVEM

Obesity-induced adipose tissue inflammation is characterized by increased macrophage infiltration and cytokine production, and is associated with metabolic disorders. LIGHT/TNFSF14, a member of the TNF superfamily, plays a role in the development of various inflammatory diseases. The purpose of this study was to examine the involvement of soluble LIGHT (sLIGHT) in obesity-induced adipose tissue inflammatory responses. LIGHT gene expression on macrophages/adipocytes was upregulated by treatment with obesity-related factors. sLIGHT displayed chemotactic activity for macrophages and T cells, and enhanced inflammatory cytokine release from macrophages, adipocytes, and adipose tissue-derived SVF cells. The sLIGHT-induced inflammatory responses were blunted by neutralizing anti-HVEM antibody or knockout of HVEM, a receptor for sLIGHT. These findings indicate that sLIGHT enhances adipose tissue inflammatory responses through its interaction with HVEM.

Slow down and survive: Enigmatic immunoregulation by BTLA and HVEM

B and T lymphocyte associated (BTLA) is an Ig domain superfamily protein with cytoplasmic immunoreceptor tyrosine-based inhibitory motifs. Its ligand, herpesvirus entry mediator (HVEM), is a tumor necrosis factor receptor superfamily member. The unique interaction between BTLA and HVEM allows for a system of bidirectional signaling that must be appropriately regulated to balance the outcome of the immune response. HVEM engagement of BTLA produces inhibitory signals through SH2 domain-containing protein tyrosine phosphatase 1 (Shp-1) and Shp-2 association, whereas BTLA engagement of HVEM produces proinflammatory signals via activation of NF-kappaB. The BTLA-HVEM interaction is intriguing and quite complex given that HVEM has four other ligands that also influence immune responses, the conventional TNF ligand LIGHT and lymphotoxin alpha, as well as herpes simplex virus glycoprotein D and the glycosylphosphatidylinositol-linked Ig domain protein CD160. BTLA-HVEM interactions have been shown to regulate responses in several pathogen and autoimmune settings, but our understanding of this complex system of interactions is certainly incomplete. Recent findings of spontaneous inflammation in BTLA-deficient mice may provide an important clue.

From gene expression to serum proteins: biomarker discovery in ankylosing spondylitis

OBJECTIVES

Studying post-infliximab gene expression changes could provide insights into the pathogenesis of ankylosing spondylitis (AS).

METHODS

Gene expression changes were screened by microarray on peripheral blood RNA of 16 AS patients at baseline and 2 weeks post-infliximab, and selected results were confirmed by quantitative real-time (qRT)-PCR. Corresponding serum-soluble LIGHT (sLIGHT) was estimated by ELISA and the fold change in sLIGHT was correlated to the fold change in erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and the Bath AS disease activity index.

RESULTS

Post-infliximab, 69% of the patients (11/16) achieved an ASAS20 response. Six candidate genes were differentially expressed by microarray; four of which were validated by qRT-PCR. sLIGHT showed the most significant difference. There was good correlation of baseline sLIGHT with CRP (R = 0.60; p = 0.01) and ESR (R = 0.51; p = 0.04). The fold change in sLIGHT correlated with change in both CRP (R = 0.71, p = 0.002) and ESR (R = 0.77, p<0.001).

CONCLUSION

LIGHT is significantly downregulated by infliximab. sLIGHT correlated well with changes in inflammatory markers.

Immunoregulation by tumor necrosis factor superfamily member LIGHT

SUMMARY

LIGHT (homologous to lymphotoxins, inducible expression, competes with herpesvirus glycoprotein D for herpesvirus entry mediator, a receptor expressed on T lymphocytes) is a member of the tumor necrosis factor superfamily that contributes to the regulation of immune responses. LIGHT can influence T-cell activation both directly and indirectly by engagement of various receptors that are expressed on T cells and on other types of cells. LIGHT, LIGHT receptors, and their related binding partners constitute a complicated molecular network in the regulation of various processes. The molecular cross-talk among LIGHT and its related molecules presents challenges and opportunities for us to study and to understand the full extent of the LIGHT function. Previous research from genetic and functional studies has demonstrated that dysregulation of LIGHT expression can result in the disturbance of T-cell homeostasis and activation, changing the ability of self-tolerance and of the control of infection. Meanwhile, blockade of LIGHT activity can ameliorate the severity of various T-cell-mediated diseases. These observations indicate the importance of LIGHT and its involvement in many physiological and pathological conditions. Understanding LIGHT interactions offers promising new therapeutic strategies that target LIGHT-engaged pathways to fight against cancer and various infectious diseases.

Targeting lymphocyte activation through the lymphotoxin and LIGHT pathways

SUMMARY

Cytokines mediate key communication pathways essential for regulation of immune responses. Full activation of antigen-responding lymphocytes requires cooperating signals from the tumor necrosis factor (TNF)-related cytokines and their specific receptors. LIGHT, a lymphotoxin-beta (LTbeta)-related TNF family member, modulates T-cell activation through two receptors, the herpesvirus entry mediator (HVEM) and indirectly through the LT-beta receptor. An unexpected finding revealed a non-canonical binding site on HVEM for the immunoglobulin superfamily member, B and T lymphocyte attenuator (BTLA), and an inhibitory signaling protein suppressing T-cell activation. Thus, HVEM can act as a molecular switch between proinflammatory and inhibitory signaling. The non-canonical HVEM-BTLA pathway also acts to counter LTbetaR signaling that promotes the proliferation of antigen-presenting dendritic cells (DCs) within lymphoid tissue microenvironments. These results indicate LTbeta receptor and HVEM-BTLA pathways form an integrated signaling circuit. Targeting these cytokine pathways with specific antagonists (antibody or decoy receptor) can alter lymphocyte differentiation and activation. Alternately, agonists directed at their cell surface receptors can restore homeostasis and potentially reset immune and inflammatory processes, which may be useful in treating autoimmune and infectious diseases and cancer.

Regulating the mucosal immune system: the contrasting roles of LIGHT, HVEM, and their various partners

LIGHT and herpes virus entry mediator (HVEM) comprise a ligand-receptor pair in the tumor necrosis factor superfamily. These molecules play an important role in regulating immunity, particularly in the intestinal mucosa. LIGHT also binds the lymphotoxin beta receptor, and HVEM can act as a ligand for immunoglobulin family molecules, including B- and T-lymphocyte attenuator, which suppresses immune responses. Complexity in this pivotal system arises from several factors, including the non-monogamous pairing of ligands and receptors, and reverse signaling or the ability of some ligands to serve as receptors. As a result, recognition events in this fascinating network of interacting molecules can have pro- or anti-inflammatory consequences. Despite complexity, experiments we and others are carrying out are establishing rules for understanding when and in what cell types these molecules contribute to intestinal inflammation.

A novel mucosal RORγtNKp46 cell subset is a source of interleukin-22

Lymphoid tissue-inducer cells are hematopoietic cells essential for the organogenesis of several lymphoid structures during both fetal and adult life, whereas natural killer cells are key effector lymphocytes of the innate immune system. A series of recent reports has identified RORγt⁺NKp46⁺ interleukin-22-producing cells in gut and tonsils that share features with both lymphoid tissue-inducer cells and natural killer cells and that may be involved in mucosal immunity and homeostasis.

Influence of the transcription factor RORgammat on the development of NKp46+ cell populations in gut and skin

NKp46+CD3- natural killer lymphocytes isolated from blood, lymphoid organs, lung, liver and uterus can produce granule-dependent cytotoxicity and interferon-gamma. Here we identify in dermis, gut lamina propria and cryptopatches distinct populations of NKp46+CD3- cells with a diminished capacity to degranulate and produce interferon-gamma. In the gut, expression of the transcription factor RORgammat, which is involved in the development of lymphoid tissue-inducer cells, defined a previously unknown subset of NKp46+CD3- lymphocytes. Unlike RORgammat- lamina propria and dermis natural killer cells, gut RORgammat+NKp46+ cells produced interleukin 22. Our data show that lymphoid tissue-inducer cells and natural killer cells shared unanticipated similarities and emphasize the heterogeneity of NKp46+CD3- cells in innate immunity, lymphoid organization and local tissue repair.

CD46-induced immunomodulatory CD4+ T cells express the adhesion molecule and chemokine receptor pattern of intestinal T cells

Tissue homing of activated T cells is typically mediated through their specific integrin and chemokine receptor repertoire. Activation of human primary CD4(+) T cells in the presence of CD46 cross-linking induces the development of a distinct immunomodulatory T cell population characterized by high IL-10/granzyme B production. How these regulatory T cells (Tregs) migrate/home to specific tissue sites is not understood. In this study, we determined the adhesion protein and chemokine receptor expression pattern on human CD3/CD46-activated peripheral blood CD4(+) T cells. CD3/CD46-activated, but not CD3/CD28-activated, T cells up-regulate the integrin alpha(4)beta(7). The interaction of alpha(4)beta(7) with its ligand mucosal addressin cell adhesion molecule 1 (MAdCAM-1) mediates homing or retention of T cells to the intestine. CD3/CD46-activated Tregs adhere to/roll on MAdCAM-1-expressing HeLa cells, similar to T cells isolated from the human lamina propria (LP). This interaction is inhibited by silencing MAdCAM-1 expression in HeLa cells or by the addition of blocking Abs to beta(7). CD46 activation of T cells also induced the expression of the surface-bound cytokine LIGHT and the chemokine receptor CCR9, both marker constitutively expressed by gut LP-resident T cells. In addition, we found that approximately 10% of the CD4(+) T lymphocytes isolated from the LP of patients undergoing bariatric surgery contain T cells that spontaneously secrete a cytokine pattern consistent with that from CD46-activated T cells. These data suggest that CD46-induced Tregs might play a role in intestinal immune homeostasis where they could dampen unwanted effector T cell responses through local IL-10/granzyme B production.

Enhanced plasma levels of LIGHT in patients with acute atherothrombotic stroke

OBJECTIVES

As a member of the tumor necrosis factor superfamily (TNFSF), LIGHT (TNFSF14) was recently found to be associated with platelets and released upon activation. Increased plasma levels of LIGHT have been reported in patients with myocardial infarction and unstable angina. The aim of the study was to analyze plasma levels of LIGHT in acute ischemic atherosclerotic stroke.

MATERIALS AND METHODS

The soluble LIGHT protein was analyzed by an enzyme-linked immunosorbent assay in peripheral blood of patients with acute ischemic atherosclerotic stroke (n = 20), asymptomatic carotid stenosis (n = 19) and normal controls (n = 23).

RESULTS

During the initial 24 h after onset, the stroke patients had an increased plasma LIGHT levels as compared with normal controls. Moreover, the plasma LIGHT levels of the stroke patients were correlated with blood platelet count (r = 0.6341, P = 0.0027).

CONCLUSION

The elevated LIGHT levels may reflect a persistent chronic inflammatory response that may have been induced during early stages of the disease. We speculate that this derangement of LIGHT may be important for atherogenetic process of ischemic stroke.

Heterogeneous memory T cells in antiviral immunity and immunopathology

Memory T cells are generated following an initial viral infection, and have the potential for mediating robust protective immunity to viral re-challenge due to their rapid and enhanced functional responses. In recent years, it has become clear that the memory T cell response to most viruses is remarkably diverse in phenotype, function, and tissue distribution, and can undergo dynamic changes during its long-term maintenance in vivo. However, the role of this variegation and compartmentalizationof memory T cells in protective immunity to viruses remains unclear. In this review,we discuss the diverse features of memory T cells that can delineate different subsets, the characteristics of memory T cells thus far identified to promote protective immune responses, and how the heterogeneous nature of memory T cells may also promote immunopathology during antiviral responses. We propose that given the profound heterogeneity of memory T cells, regulation of memory T cells during secondary responses could focus the response to participation of specific subsets,and/or inhibit memory T-cell subsets and functions that can lead to immunopathology.

Body traffic: ecology, genetics, and immunity in inflammatory bowel disease

The abundant bacteria and other microbial residents of the human intestine play important roles in nutrient absorption, energy metabolism, and defense against microbial pathogens. The mutually beneficial relationship of host and commensal microbiota represents an ancient and major coevolution in composition and mutual regulation of the human mucosa and the resident microbial community. Inflammatory bowel disease (IBD) is a set of chronic, relapsing inflammatory intestinal diseases in which rules of normal host-microbial interaction have been violated. This review considers the components of this host-microbial mutualism and the ways in which it is undermined by pathogenic microbial traits and by host immune and epithelial functions that confer to them susceptibility in patients with IBD. Recent advances in understanding the genetics of IBD and the immunology of host-microbial interaction are opening new strategies for treatments that target host susceptibility, candidate microbial pathogens, and intestinal ecology.

NK but not CD1-restricted NKT cells facilitate systemic inflammation during polymicrobial intra-abdominal sepsis

Evidence suggests that NK and NKT cells contribute to inflammation and mortality during septic shock caused by cecal ligation and puncture (CLP). However, the specific contributions of these cell types to the pathogenesis of CLP-induced septic shock have not been fully defined. The goal of the present study was to determine the mechanisms by which NK and NKT cells mediate the host response to CLP. Control, NK cell-deficient, and NKT cell-deficient mice underwent CLP. Survival, cytokine production, and bacterial clearance were measured. NK cell trafficking and interaction with myeloid cells was also studied. Results show that mice treated with anti-asialoGM1 (NK cell deficient) or anti-NK1.1 (NK/NKT cell deficient) show less systemic inflammation and have improved survival compared with IgG-treated controls. CD1 knockout mice (NKT cell deficient) did not demonstrate decreased cytokine production or improved survival compared with wild type mice. Trafficking studies show migration of NK cells from blood and spleen into the inflamed peritoneal cavity where they appear to facilitate the activation of peritoneal macrophages (F4-80(+)GR-1(-)) and F4-80(+)Gr-1(+) myeloid cells. These findings indicate that NK but not CD1-restricted NKT cells contribute to acute CLP-induced inflammation. NK cells appear to mediate their proinflammatory functions during septic shock, in part, by migration into the peritoneal cavity and amplification of the proinflammatory activities of specific myeloid cell populations. These findings provide new insights into the mechanisms used by NK cells to facilitate acute inflammation during septic shock.

A crucial role for HVEM and BTLA in preventing intestinal inflammation

The interaction between the tumor necrosis factor (TNF) family member LIGHT and the TNF family receptor herpes virus entry mediator (HVEM) co-stimulates T cells and promotes inflammation. However, HVEM also triggers inhibitory signals by acting as a ligand that binds to B and T lymphocyte attenuator (BTLA), an immunoglobulin super family member. The contribution of HVEM interacting with these two binding partners in inflammatory processes remains unknown. In this study, we investigated the role of HVEM in the development of colitis induced by the transfer of CD4(+)CD45RB(high) T cells into recombination activating gene (Rag)(-/-) mice. Although the absence of HVEM on the donor T cells led to a slight decrease in pathogenesis, surprisingly, the absence of HVEM in the Rag(-/-) recipients led to the opposite effect, a dramatic acceleration of intestinal inflammation. Furthermore, the critical role of HVEM in preventing colitis acceleration mainly involved HVEM expression by radioresistant cells in the Rag(-/-) recipients interacting with BTLA. Our experiments emphasize the antiinflammatory role of HVEM and the importance of HVEM expression by innate immune cells in preventing runaway inflammation in the intestine.

Promoter sequence variants of LIGHT are associated with female vascular dementia

LIGHT (homologous to L ymphotoxins, exhibits I nducible expression, and competes with herpes simplex virus G lycoprotein D for H erpes virus entry mediator, a receptor expressed by T lymphocytes) is implicated in the inflammation by disrupted T cell homeostasis, primarily at a transcriptional level. We investigated the association of LIGHT promoter with ischemic stroke and vascular dementia induced by such inflammation. We determined transcription factor binding sites altered by promoter SNPs using transcription factor prediction programs. Six common haplotypes composed of the selected SNPs (C-770T, G-607T, G-543A, and A-399G) were used for the assay of reporter activity. The most frequent haplotype construct, CGGA, induced the highest luciferase activity. The haplotype TTGA showed the lowest expression with 0.39-fold activity (P < 0.001) of CGGA. The substitution from C to T at the locus of C-770T (TGGA) decreased the reporter activity by 47% (P < 0.001). The SNPs and haplotypes were further investigated to see their association with ischemic stroke and vascular dementia in 455 controls and 478 patients. Significant association with vascular dementia was shown in the allele T of C-770T (odds ratio [OR] = 1.54; P < 0.05) and the haplotype TTGA (OR = 10.59; P < 0.05) in females. We concluded that the allele T of C-770T and the haplotype TTGA of the promoter SNPs in LIGHT gene might decrease the expression of LIGHT and subsequently increase the susceptibility to vascular dementia in females.

Immunopathogenesis of inflammatory bowel disease

Crohn’s disease and ulcerative colitis are chronic relapsing immune mediated disorders that results from an aberrant response to gut luminal antigen in genetically susceptible host. The adaptive immune response that is then triggered was widely considered to be a T-helper-1 mediated condition in Crohn’s disease and T-helper-2 mediated condition in ulcerative colitis. Recent studies in animal models, genome wide association, and basic science has provided important insights in in the immunopathogenesis of inflammatory bowel disease, one of which was the characterization of the interleukin-23/Th-17 axis.

LIGHT--a new member of the TNF superfamily in the plasma, dialysate and urine of uremic patients; the impact of residual diuresis and presence of viral hepatitis

OBJECTIVES

LIGHT is a cytokine involved in atherosclerosis and cardiovascular disease in general population.

DESIGN AND METHODS

We determined the levels of LIGHT in the plasma, dialysate and urine of uremic patients undergoing hemodialysis (HD) and healthy controls.

RESULTS

There were no significant differences in the pre and post-HD plasma levels of LIGHT between HD patients with residual diuresis (HD-RD) and HD anuric group (HD-A) compared to controls. HD-RD patients had the lower LIGHT values in dialysate compared to HD-A patients (p<0.001), and higher urinary LIGHT excretion compared to controls (p<0.05). Moreover, the presence of RD and chronic viral hepatitis were independent factors influencing the levels of this cytokine in dialysate.

CONCLUSIONS

The plasma levels of LIGHT seem to be similar in HD patients and healthy subjects and were not affected by gender, age, the mean period of HD history, disease etiology, type of medication and type of using dialysis membrane.

Chronic viral hepatitis and iron affect the plasma levels of LIGHT--a new member of the TNF superfamily in uraemic haemodialyzed patients

LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for binding herpesvirus entry mediator on T cells) is a recently identified of the tumor necrosis factor alpha (TNF-alpha) ligand superfamily. We wanted to establish whether the presence of chronic viral hepatitis could be implicated in enhanced inflammation as well as the elevation of plasma LIGHT levels in haemodialyzed (HD) patients. The plasma levels of LIGHT, high sensitivity C-reactive protein (hs CRP) and TNF-alpha were measured in HD patients with hepatitis in comparison to subjects without hepatitis and to healthy volunteers. The values of hs CRP and TNF-alpha were significantly elevated in HD patients when compared to the controls. TNF-alpha levels were significantly higher in the hepatitis-positive relative to the hepatitis-negative group (p <0.01). LIGHT levels were significantly decreased in hepatitis-negative patients as compared to controls (p <0.001) and hepatitis-positive group (p < 0.01). Both LIGHT and TNF-alpha were directly associated with the presence of hepatitis. Multiple stepwise regression analysis identified increased iron levels as the only independent variable significantly associated with increased LIGHT (beta=0.475, p=0.003). These results suggest the presence of chronic viral hepatitis and iron levels are novel determinants of the increased LIGHT in the plasma of HD patients.

Platelet-derived LIGHT induces inflammatory responses in endothelial cells and monocytes

Traditionally, platelets are known to play an important role in hemostasis, thrombosis, and wound healing, but increasing evidence suggests that activated platelets also may promote inflammation. Platelet-induced modulation of inflammation seems to involve platelet expression of ligands in the tumor necrosis factor (TNF) superfamily such as CD40 ligand and Fas ligand. The present study demonstrates that LIGHT, another member of the TNF superfamily, is associated with platelets and is released as a soluble ligand on platelet activation. The release of LIGHT involves GP IIb/IIIa-dependent mechanisms and action of metal-dependent proteases as well as intracellular processes such as actin polymerization. We also report that platelet-derived LIGHT is biologically active and can induce an inflammatory response in monocytes and particularly within endothelial cells measured as up-regulation of adhesion molecules and release of chemokines. Moreover, we demonstrate that thrombus material, obtained at the site of plaque rupture in patients with acute myocardial infarction, contains platelet-associated LIGHT, suggesting that LIGHT-mediated inflammation also is operating in vivo within an inflamed and thrombotic vessel wall. The data may suggest a pathogenic role for platelet-derived LIGHT in atherogenesis and plaque destabilization as well as in other inflammatory disorders involving leukocyte infiltration into the vessel wall.

BAFF induces a hyper-IgA syndrome in the intestinal lamina propria concomitant with IgA deposition in the kidney independent of LIGHT

BAFF is a peripheral B cell survival factor and can mediate antibody (Ab) class switching. Over-expression of BAFF in mice results in B cell hyperplasia, elevated serum immunoglobulin (Ig), spontaneous germinal centre (GC) reactions and mild glomerulonephritis (GN). Here we show that, in addition to driving excessive levels of serum IgA, BAFF over-expression results in increased IgA levels within the intestinal lamina propria (LP) and deposition of IgA immune complexes in the renal glomerular mesangium. LIGHT has been previously shown to mediate a similar phenotype via signaling through the lymphotoxin-beta receptor (LTbetaR). We evaluated if LIGHT and BAFF cooperate in the etiology of a hyper-IgA syndrome in BAFF-overexpressing transgenic (BAFF-Tg) mice. We find that LIGHT-deficient BAFF-Tg mice exhibit similar levels of IgA in the serum, gut and kidney and develop nephritis to the same degree as LIGHT-sufficient BAFF-Tg mice. Therefore, in the context of BAFF over-expression, LIGHT is dispensable for the generation of a hyper-IgA syndrome accompanied by nephritis.

LIGHT is dispensable for CD4+ and CD8+ T cell and antibody responses to influenza A virus in mice

The tumor necrosis factor family ligands, LIGHT (lymphotoxin like, exhibits inducible expression and competes with HSV glycoprotein D for HVEM, a receptor expressed by T lymphocytes), 4-1BBL and CD70, are found in the same gene cluster on mouse chromosome 17. Although the roles of 4-1BB-4-1BBL and CD27-CD70 interactions in anti-viral T cell responses have been well established, the role of LIGHT in T cell activation/expansion in vivo is less clear. Under conditions that were previously employed to demonstrate a role for 4-1BBL in CD8+ T cell memory, wild-type and LIGHT-/- mice were infected with influenza A virus and primary and memory/recall responses were measured at various time points thereafter. Neither primary expansion nor memory/recall CD8+ T cell responses were affected by the absence of LIGHT, as measured up to 2 months post-infection. CD4+ T cell responses were also unaffected by LIGHT deficiency. Furthermore, we found that LIGHT played no role in the induction of influenza-specific IgG1 and IgG2a serum antibodies. Taken together, these data suggest that LIGHT is dispensable for the acquired immune response to influenza virus in mice with no effect on the induction, maintenance or reactivation of CD8+ T cell memory.