Immunoregulation by tumor necrosis factor superfamily member LIGHT

Etiopathogenesis of primary acquired nasolacrimal duct obstruction (PANDO)

Primary acquired nasolacrimal duct obstruction, or PANDO, is a common adult lacrimal drainage disorder. The current treatment modality of dacryocystorhinostomy to bypass the obstructed nasolacrimal duct has excellent outcomes. However, the understanding of the disease etiopathogenesis needs to be revisited. There are not many studies that specifically assessed any hypothesis or ones that convincingly put forth the presumed or confirmed interpretations regarding the PANDO pathogenesis or the mechanisms or pathways involved therein. Histopathological evidence points to recurrent inflammation of the nasolacrimal duct, subsequent fibrosis, and the resultant obstruction. The disease etiopathogenesis is considered multifactorial. Several implicated suspects include anatomical narrowing of the bony nasolacrimal duct, vascular factors, local hormonal imbalance, microbial influence, nasal abnormalities, autonomic dysregulation, surfactants, lysosomal dysfunction, gastroesophageal reflux, tear proteins, and deranged local host defenses. The present work reviewed the literature on the etiopathogenesis of primary acquired nasolacrimal duct obstruction (PANDO) to gain insights into the present state of the understanding and the high-value translational implications of precisely decoding the disease etiology.

Shining a LIGHT on myeloid cell targeted immunotherapy

Despite over a decade of clinical trials combining inhibition of emerging checkpoints with a PD-1/L1 inhibitor backbone, meaningful survival benefits have not been shown in PD-1/L1 inhibitor resistant or refractory solid tumours, particularly tumours dominated by a myelosuppressive microenvironment. Achieving durable anti-tumour immunity will therefore likely require combination of adaptive and innate immune stimulation, myeloid repolarisation, enhanced APC activation and antigen processing/presentation, lifting of the CD47/SIRPα (Cluster of Differentiation 47/signal regulatory protein alpha) 'do not eat me' signal, provision of an apoptotic 'pro-eat me' or 'find me' signal, and blockade of immune checkpoints. The importance of effectively targeting mLILRB2 and SIRPAyeloid cells to achieve improved response rates has recently been emphasised, given myeloid cells are abundant in the tumour microenvironment of most solid tumours. TNFSF14, or LIGHT, is a tumour necrosis superfamily ligand with a broad range of adaptive and innate immune activities, including (1) myeloid cell activation through Lymphotoxin Beta Receptor (LTβR), (2) T/NK (T cell and natural killer cell) induced anti-tumour immune activity through Herpes virus entry mediator (HVEM), (3) potentiation of proinflammatory cytokine/chemokine secretion through LTβR on tumour stromal cells, (4) direct induction of tumour cell apoptosis in vitro, and (5) the reorganisation of lymphatic tissue architecture, including within the tumour microenvironment (TME), by promoting high endothelial venule (HEV) formation and induction of tertiary lymphoid structures. LTBR (Lymphotoxin beta receptor) and HVEM rank highly amongst a range of costimulatory receptors in solid tumours, which raises interest in considering how LIGHT-mediated costimulation may be distinct from a growing list of immunotherapy targets which have failed to provide survival benefit as monotherapy or in combination with PD-1 inhibitors, particularly in the checkpoint acquired resistant setting.

Herpesvirus entry mediator regulates the transduction of Tregs via STAT5/Foxp3 signaling pathway in ovarian cancer cells

The ratio of regulatory T cells (Treg) in peripheral blood of cancer patients has a closely correlation to the occurrence and development of ovarian cancer. In this study, our aim to explore the expression of herpesvirus entry mediator (HVEM) in ovarian cancer and its correlation with Tregs. The expression of HVEM in peripheral blood of ovarian cancer patients was detected by ELISA, and the ratio of CD4+ CD25 + Foxp3 positive Tregs cells was detected by flow cytometry. Ovarian cancer cell lines with high- and low-HVEM expression were constructed. CD4+ cells were co-cultured with ovarian cancer (OC) cells, and the expressions of IL-2 and TGF-β1 in the supernatant of cells were detected by ELISA, and western blot was used to detect the expressions of STAT5, p-STAT5, and Foxp3. The results indicated that the number of Treg cells in the peripheral blood of OC patients increased, and the expression of HVEM increased, the two have a certain correlation. At the same time, the overexpression of HVEM promoted the expression of cytokines IL-2 and TGF- β1, promoted the activation of STAT5 and the expression of Foxp3, leading to an increase in the positive rate of Treg, while the HVEM gene silence group was just the opposite. Our results showed that the expression of HVEM in OC cells has a positive regulation effect on Tregs through the STAT5/Foxp3 signaling pathway. To provide experimental basis and related mechanism for the clinical treatment of ovarian cancer.

The tumor necrosis factor family molecules LIGHT and lymphotoxins in sinus mucosa of patients with chronic rhinosinusitis with or without nasal polyps

BACKGROUND

Little is known about the role of lymphotoxins (LTs) family in the sinonasal mucosa of patients with chronic rhinosinusitis (CRS). This study aims at investigating the expression of LIGHT, LTα, LTβ, and their receptors, LTβR and HVEM in normal and inflammatory sinus mucosa, and the effect of LIGHT and LTalpha1beta2 on chemokine secretion in epithelial cells, epithelial permeability, and leukocyte migration.

MATERIAL AND METHODS

The expression of LTs family in sinonasal mucosa was evaluated with real-time PCR, immunohistochemistry, and western blot. In LTβR, HVEM siRNA, or control siRNA-transfected epithelial cells treated with LIGHT or LTalpha1beta2, the expression of chemokines, the epithelial permeability, and the expression of junctional complex proteins were evaluated using real-time PCR, ELISA, western blot, confocal microscopy, and FITC-dextran. In cultured endothelial cells treated with LIGHT or LTalpha1beta2, the expression of ICAM-1 and VCAM-1, and leukocyte migration were elucidated.

RESULTS

LTs family was expressed in normal mucosa and their levels were increased in inflammatory mucosa of CRS patients. Recombinant LIGHT and LTalpha1beta2 induced chemokine secretion, increased epithelial permeability, and promoted leukocyte migration. However, the activity of LIGHT and LTalpha1beta2 was attenuated in cells transfected with LTβR and HVEM siRNA.

CONCLUSIONS

LIGHT and LTs may participate in the ongoing process of chronic inflammation, inducing chemokine secretion, leukocyte migration, and dysregulated epithelial barrier through LTβR and HVEM in sinonasal mucosa.

Metabolic activation and colitis pathogenesis is prevented by lymphotoxin β receptor expression in neutrophils

Inflammatory bowel disease is characterized by an exacerbated intestinal immune response, but the critical mechanisms regulating immune activation remain incompletely understood. We previously reported that the TNF-superfamily molecule TNFSF14 (LIGHT) is required for preventing severe disease in mouse models of colitis. In addition, deletion of lymphotoxin beta receptor (LTβR), which binds LIGHT, also led to aggravated colitis pathogenesis. Here, we aimed to determine the cell type(s) requiring LTβR and the mechanism critical for exacerbation of colitis. Specific deletion of LTβR in neutrophils (LTβRΔN), but not in several other cell types, was sufficient to induce aggravated colitis and colonic neutrophil accumulation. Mechanistically, RNA-Seq analysis revealed LIGHT-induced suppression of cellular metabolism, and mitochondrial function, that was dependent on LTβR. Functional studies confirmed increased mitochondrial mass and activity, associated with excessive mitochondrial ROS production and elevated glycolysis at steady-state and during colitis. Targeting these metabolic changes rescued exacerbated disease severity. Our results demonstrate that LIGHT signals to LTβR on neutrophils to suppress metabolic activation and thereby prevents exacerbated immune pathogenesis during colitis.

LIGHT/LTβR signaling regulates self-renewal and differentiation of hematopoietic and leukemia stem cells

The production of blood cells during steady-state and increased demand depends on the regulation of hematopoietic stem cell (HSC) self-renewal and differentiation. Similarly, the balance between self-renewal and differentiation of leukemia stem cells (LSCs) is crucial in the pathogenesis of leukemia. Here, we document that the TNF receptor superfamily member lymphotoxin-β receptor (LTβR) and its ligand LIGHT regulate quiescence and self-renewal of murine and human HSCs and LSCs. Cell-autonomous LIGHT/LTβR signaling on HSCs reduces cell cycling, promotes symmetric cell division and prevents primitive HSCs from exhaustion in serial re-transplantation experiments and genotoxic stress. LTβR deficiency reduces the numbers of LSCs and prolongs survival in a murine chronic myeloid leukemia (CML) model. Similarly, LIGHT/LTβR signaling in human G-CSF mobilized HSCs and human LSCs results in increased colony forming capacity in vitro. Thus, our results define LIGHT/LTβR signaling as an important pathway in the regulation of the self-renewal of HSCs and LSCs.

Programming CAR T cells to enhance anti-tumor efficacy through remodeling of the immune system

Chimeric antigen receptor (CAR) T cells have been indicated effective in treating B cell acute lymphoblastic leukemia and non-Hodgkin lymphoma and have shown encouraging results in preclinical and clinical studies. However, CAR T cells have achieved minimal success against solid malignancies because of the additional obstacles of their insufficient migration into tumors and poor amplification and persistence, in addition to antigen-negative relapse and an immunosuppressive microenvironment. Various preclinical studies are exploring strategies to overcome the above challenges. Mobilization of endogenous immune cells is also necessary for CAR T cells to obtain their optimal therapeutic effect given the importance of the innate immune responses in the elimination of malignant tumors. In this review, we focus on the recent advances in the engineering of CAR T cell therapies to restore the immune response in solid malignancies, especially with CAR T cells acting as cellular carriers to deliver immunomodulators to tumors to mobilize the endogenous immune response. We also explored the sensitizing effects of conventional treatment approaches, such as chemotherapy and radiotherapy, on CAR T cell therapy. Finally, we discuss the combination of CAR T cells with biomaterials or oncolytic viruses to enhance the anti-tumor outcomes of CAR T cell therapies in solid tumors.

Langerhans Cells Control Lymphatic Vessel Function during Inflammation via LIGHT-LTβR Signaling

The lymphatic vasculature is an important route for dendritic cell (DC) or tumor cell migration from peripheral tissues to draining lymph nodes (DLNs). However, the underlying molecular and cellular mechanisms remain poorly understood. In this study, using conventional bone marrow chimeric mice and additional UVB radiation, we found that deficiency of LIGHT but not lymphotoxin (LT) α1β2, likely on radioresistant Langerhans cells (LCs), resulted in impaired skin DC migration to DLNs during LPS-induced inflammation. In addition, LT β receptor (LTβR), but not herpes virus entry mediator, was found to be the receptor of LIGHT controlling DC migration. Furthermore, conditional deficiency of LTβR in Tie2 ^cre or Lyve1 ^cre mice, but not in LTβR-deficient bone marrow chimeric mice, impaired DC migration, suggesting an important role of LTβR in radioresistant lymphatic endothelial cells (LECs), although the role of LTβR in blood endothelial cells remains intriguing. Mechanistically, the gene expression of both CCL21 and CCL19 was found to be reduced in skin LECs isolated from LC-LIGHT-conditionally deficient or Lyve1 ^cre Ltbr ^fl/fl mice compared with their controls upon LPS stimulation. Soluble recombinant LIGHT was able to upregulate CCL21 and CCL19 gene expression on SVEC4-10 endothelial cells. Doxycycline, an inhibitor of soluble LIGHT release in the inflamed skin, impaired skin CCL21 and CCL19 expression and DC migration. In addition, melanoma cell metastasis to DLNs was also inhibited in LC-LIGHT-conditionally deficient or Lyve1 ^cre Ltbr ^fl/fl mice. Together, our data suggest, to our knowledge, a previously unrecognized scenario in which LCs activate LECs via the LIGHT-LTβR signaling axis to promote DC migration or tumor cell metastasis.

Targeting tumor cells with antibodies enhances anti-tumor immunity

Tumor-targeting antibodies were initially defined as a group of therapeutic monoclonal antibodies (mAb) that recognize tumor-specific membrane proteins, block cell signaling, and induce tumor-killing through Fc-driven innate immune responses. However, in the past decade, ample evidence has shown that tumor-targeting mAb (TTmAb) eradicates tumor cells via activation of cytotoxic T cells (CTLs). In this review, we specifically focus on how TTmAbs induce adaptive anti-tumor immunity and its potential in combination therapy with immune cytokines, checkpoint blockade, radiation, and enzyme-targeted small molecule drugs. Exploring the mechanisms of these preclinical studies and retrospective clinical data will significantly benefit the development of highly efficient and specific TTmAb-oriented anti-tumor remedies.

Effects of inhaled corticosteroids on the expression of TNF family molecules in murine model of allergic asthma

BACKGROUND

The tumor necrosis factor superfamily member LIGHT (the official gene symbol approved by NCBI Gene Database), an inflammatory factor secreted by T cells after allergen exposure, recently discovered to play crucial roles in asthmatic airway remodeling. However, it is unclear whether LIGHT could be controlled by inhaled corticosteroids, a key component of asthma management. This study was to investigate the effects and potential mechanisms of inhaled budesonide on the expressions of LIGHT and its receptors (LTβR and HVEM) of lung tissues in ovalbumin-sensitized mice.

MATERIALS AND METHODS

Thirty-three BALB/c mice were randomly divided into the control, asthma model, and budesonide treatment groups (11 in each group). Mice were sensitized and challenged by OVA to develop mouse model of chronic asthma, and treated with aerosolized budesonide before OVA challenge. Bronchoalveolar lavage fluid (BALF) and lungs were obtained after the final OVA challenge. Protein and mRNA Levels of LIGHT, LTβR, and HVEM in the lungs were investigated by immunohistochemistry, image analysis, and real-time PCR. Expressions of IL-6 and IFN-γ in BALF were measured by ELISA.

RESULTS

Inhaled budesonide significantly reduced protein and mRNA levels of lung LIGHT, LTβR, and HVEM in asthmatic mice. Correspondingly, the number of eosinophils and neutrophils and IL-6 levels in BALF after budesonide treatment were found to be decreased, whereas the IFN-γ levels in BALF were increased. Moreover, the expressions of LIGHT and HVEM mRNA showed positive correlation with IL-6 levels in the treatment group.

CONCLUSIONS

Inhaled budesonide can down-regulate the expressions of LIGHT, LTβR, and HVEM in the lungs of asthmatic mice, and LIGHT/LTβR/HVEM interactions may be a potentially key target for asthma treatment.

Strategies for Bispecific Single Chain Antibody in Cancer Immunotherapy

Genetic engineering has resulted in more than 50 recombinant bispecific antibody formats over the past two decades. Bispecific scFv antibodies represent a successful and promising immunotherapy platform that retargets cytotoxic T cells to tumor cells, with one scFv directed to tumor-associated antigens and the other to T cells. Based on this antibody construct, strategies for both specific tumor targeting and T cell activation are reviewed here. Three distinct types of tumor antigens are considered to optimize specificity and safety in bispecific scFv based treatment: cancer-testis antigens, neo-antigens and virus-associated antigens. In terms of T cell activation, although CD3 has been widely applied in bispecific scFvs being developed, CD28 and CD137 among co-stimulatory signals are also ideal candidates to be evaluated. Besides, LIGHT and HIV-Tat101 have drawn much attention as their potential roles in modulating antitumor responses.

Lymphotoxin signalling in tertiary lymphoid structures and immunotherapy

Tertiary lymphoid structures (TLS) often develop at sites of persistent inflammation, including cancers and autoimmune diseases. In most cases, the presence of TLS correlates with active immune responses. Because of their proximity to pathological loci, TLS are an intriguing target for the manipulation of immune responses. For several years, it has become clear that lymphotoxin (LT) signalling plays critical roles in lymphoid tissue organogenesis and maintenance. In the current review, we will discuss the role of LT signalling in the development of TLS. With a focus on cancers and autoimmune diseases, we will highlight the correlations between TLS and disease progression. We will also discuss the current efforts and potential directions for manipulating TLS for immunotherapies.

Facilitating T Cell Infiltration in Tumor Microenvironment Overcomes Resistance to PD-L1 Blockade

Immune checkpoint blockade therapies fail to induce responses in the majority of cancer patients, so how to increase the objective response rate becomes an urgent challenge. Here, we demonstrate that sufficient T cell infiltration in tumor tissues is a prerequisite for response to PD-L1 blockade. Targeting tumors with tumor necrosis factor superfamily member LIGHT activates lymphotoxin β-receptor signaling, leading to the production of chemokines that recruit massive numbers of T cells. Furthermore, targeting non-T cell-inflamed tumor tissues by antibody-guided LIGHT creates a T cell-inflamed microenvironment and overcomes tumor resistance to checkpoint blockade. Our data indicate that targeting LIGHT might be a potent strategy to increase the responses to checkpoint blockades and other immunotherapies in non-T cell-inflamed tumors.

Converging mediators from immune and trophic pathways to identify Parkinson disease dementia

Objective:

To identify a panel of peripheral inflammatory/immune mediators that could discriminate Parkinson disease with dementia (PDD) from Parkinson disease (PD) without dementia.

Methods:

Plasma samples from 52 patients with PD and 22 patients with PDD were prepared from freshly collected blood following an institutional review board–approved protocol. A total of 160 proteins were measured using a multiplex antibody array. Plasma α-synuclein levels were analyzed by an electrochemiluminescence immunoassay. The main objective of the statistical analyses was to identify PDD discriminants using the plasma protein profile alone or in combination with age.

Results:

The PD and PDD groups differed significantly in cognitive measurements (Mini-Mental State Examination, Auditory Verbal Learning Test-A7, and Clinical Dementia Rating) and age. The age-adjusted levels of thymus and activation-regulated chemokine (TARC) and platelet-derived growth factor (PDGF)-AA were significantly different between disease groups. The levels of plasma α-synuclein significantly correlated with 26 proteins; among them, PDGF-BB, TARC, PDGF-AA, and epidermal growth factor were the highest. Linear discriminant analysis with leave-one-out cross-validation identified a 14-protein panel with age as discriminants of PDD (96% sensitivity, 89% specificity, area under the curve = 0.9615).

Conclusions:

We showed that multiple proteins that are mediators of growth/trophic and immune response-related pathways had discriminatory power for identifying PDD in patients with PD. Validation of this discovery-based study in longitudinal population-based studies is warranted.

Classification of evidence:

This study provides Class III evidence that a 14-protein panel plasma assay combined with age has a sensitivity of 96% and a specificity of 89% for PDD.

Immunotherapy and tumor microenvironment

Recent exciting progress in cancer immunotherapy has ushered in a new era of cancer treatment. Immunotherapy can elicit unprecedented durable responses in advanced cancer patients that are much greater than conventional chemotherapy. However, such responses only occur in a relatively small fraction of patients. A positive response to immunotherapy usually relies on dynamic interactions between tumor cells and immunomodulators inside the tumor microenvironment (TME). Depending on the context of these interactions, the TME may play important roles to either dampen or enhance immune responses. Understanding the interactions between immunotherapy and the TME is not only critical to dissect the mechanisms of action but also important to provide new approaches in improving the efficiency of current immunotherapies. In this review, we will highlight recent work on how the TME can influence the efficacy of immunotherapy as well as how manipulating the TME can improve current immunotherapy regimens in some cases.

Trans-system mechanisms against ischemic myocardial injury

A mammalian organism possesses a hierarchy of naturally evolved protective mechanisms against ischemic myocardial injury at the molecular, cellular, and organ levels. These mechanisms comprise regional protective processes, including upregulation and secretion of paracrine cell-survival factors, inflammation, angiogenesis, fibrosis, and resident stem cell-based cardiomyocyte regeneration. There are also interactive protective processes between the injured heart, circulation, and selected remote organs, defined as trans-system protective mechanisms, including upregulation and secretion of endocrine cell-survival factors from the liver and adipose tissue as well as mobilization of bone marrow, splenic, and hepatic cells to the injury site to mediate myocardial protection and repair. The injured heart and activated remote organs exploit molecular and cellular processes, including signal transduction, gene expression, cell proliferation, differentiation, migration, mobilization, and/or extracellular matrix production, to establish protective mechanisms. Both regional and trans-system cardioprotective mechanisms are mediated by paracrine and endocrine messengers and act in coordination and synergy to maximize the protective effect, minimize myocardial infarction, and improve myocardial function, ensuring the survival and timely repair of the injured heart. The concept of the trans-system protective mechanisms may be generalized to other organ systems-injury in one organ may initiate regional as well as trans-system protective responses, thereby minimizing injury and ensuring the survival of the entire organism. Selected trans-system processes may serve as core protective mechanisms that can be exploited by selected organs in injury. These naturally evolved protective mechanisms are the foundation for developing protective strategies for myocardial infarction and injury-induced disorders in other organ systems.

Shedding LIGHT (TNFSF14) on the tumor microenvironment of colorectal cancer liver metastases

Background

T-cell infiltration in primary colon tumors is associated with improved patient survival. Preliminary data supports a similar association in colorectal liver metastases (CRLM), and we previously identified increased CRLM expression of the immunostimulatory cytokine LIGHT (TNFSF14) to be related to improved patient prognosis. Therefore, mechanisms to augment the T-cell response in CRLM may be a promising treatment modality, however, the tumor immune microenvironment and LIGHT expression in CRLM remains to be characterized.

Methods

Utilizing a syngeneic and immunocompetent model of CRLM, the immune microenvironment was characterized for lymphocyte phenotype, function, and location utilizing flow cytometry, immunoassays, and immunofluorescence microscopy.

Results

CD3+ and CD4+ lymphocytes were decreased, and CD8+ cells were increased in CRLM compared to control liver. When present, greater populations of tumor infiltrating lymphocytes (TIL) were found peritumoral than intratumoral. The TIL expressed significantly higher levels of CD69 and CD107a, but lower levels of LIGHT. Cytokine expression profiles revealed increased levels of the T-helper 1 (Th1) cytokines IFN gamma, IL-12, IL-1b, and IL-8 in CRLM compared to control liver tissue. There was no difference in T-helper 2 (Th2) cytokines between the groups.

Conclusions

Characterization of the tumor microenvironment of CRLM revealed that although a limited number of activated T-cells infiltrate the tumor and initiate an immune response, the number of LIGHT + T cells infiltrating the tumor were very low. Techniques to decrease suppressive influences or augment the cytotoxic T-cell response are needed and may be possible through mechanisms that can increase intratumoral TIL LIGHT expression.

The risks of targeting co-inhibitory pathways to modulate pathogen-directed T cell responses

The identification of T cell co-inhibition as a central mechanism in the regulation of adaptive immunity during infectious diseases provides new opportunities for immunotherapeutic interventions. However, the fact that T cell activity is frequently downregulated during pathogen-directed responses suggests a pivotal physiological role of co-inhibitory pathways during infectious disease. Reports of exacerbated immunopathology in conditions of impaired co-inhibition foster the view that downregulation of T cell activity is an essential negative feedback mechanism that protects from excessive pathogen-directed immunity. Thus, targeting co-inhibitory pathways can bear detrimental potential through the deregulation of physiological processes. Here, we summarize recent preclinical and clinical interventions that report immune-related adverse events after targeting co-inhibitory pathways.

Host gene expression signatures discriminate between ferrets infected with genetically similar H1N1 strains

Different respiratory viruses induce virus-specific gene expression in the host. Recent evidence, including those presented here, suggests that genetically related isolates of influenza virus induce strain-specific host gene regulation in several animal models. Here, we identified systemic strain-specific gene expression signatures in ferrets infected with pandemic influenza A/California/07/2009, A/Mexico/4482/2009 or seasonal influenza A/Brisbane/59/2007. Using uncorrelated shrunken centroid classification, we were able to accurately identify the infecting influenza strain with a combined gene expression profile of 10 selected genes, independent of the severity of disease. Another gene signature, consisting of 7 genes, could classify samples based on lung pathology. Furthermore, we identified a gene expression profile consisting of 31 probes that could classify samples based on both strain and severity of disease. Thus, we show that expression-based analysis of non-infected tissue enables distinction between genetically related influenza viruses as well as lung pathology. These results open for development of alternative tools for influenza diagnostics.

The role of core TNF/LIGHT family members in lymph node homeostasis and remodeling

Lymph nodes (LNs) maintain active homeostasis at steady state. However, in response to changes in the local environment, such as local infection, cancer, vaccination, and autoimmune disease, dramatic remodeling of LN occurs. This remodeling includes changes in size, lymph and blood flow, immune cell trafficking and cellularity, lymphatic and blood vessel growth and activation, as well as microarchitecture. Therefore, inflammatory conditions often lead to enlarged nodes; after local inflammation resolves, LNs actively regress in size and return to steady state. Remodeling of lymphatic vessels (LVs) and blood vessels (BVs) during both the expansion and regression phases are key steps in controlling LN size as well as function. The cells, membrane-associated molecules, and soluble cytokines that are essential for LV and BV homeostasis as well as dynamic changes in the expansion and regression phases have not been well defined. Understanding the underlying cellular and molecular mechanisms behind LN remodeling would help us to better control undesired immune responses (e.g. inflammation and autoimmune diseases) or promote desired responses (e.g. antitumor immunity and vaccination). In this review, we focus on how the closely related tumor necrosis factor (TNF) members: LIGHT (TNFSF14), lymphotoxin-αβ, and TNF-α contribute to the remodeling of LNs at various stages of inflammation.

Genetics of experimental allergic encephalomyelitis supports the role of T helper cells in multiple sclerosis pathogenesis

OBJECTIVE

The major histocompatibility complex (MHC) is the primary genetic contributor to multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), but multiple additional interacting loci are required for genetic susceptibility. The identity of most of these non-MHC genes is unknown. In this report, we identify genes within evolutionarily conserved genetic pathways leading to MS and EAE.

METHODS

To identify non-MHC binary and quantitative trait loci (BTL/QTL) important in the pathogenesis of EAE, we generated phenotype-selected congenic mice using EAE-resistant B10.S and EAE-susceptible SJL mice. We hypothesized that genes linked to EAE BTL/QTL and MS-GWAS can be identified if they belong to common evolutionarily conserved pathways, which can be identified with a bioinformatic approach using Ingenuity software.

RESULTS

Many known BTL/QTL were retained and linked to susceptibility during phenotype selection, the most significant being a region on chromosome 17 distal to H2 (Eae5). We show in pathway analysis that T helper (T(H))-cell differentiation genes are critical for both diseases. Bioinformatic analyses predicted that Eae5 is important in CD4 T-effector and/or Foxp3(+) T-regulatory cells (Tregs), and we found that B10.S-Eae5(SJL) congenic mice have significantly greater numbers of lymph node CD4 and Tregs than B10.S mice.

INTERPRETATION

These results support the polygenic model of MS/EAE, whereby MHC and multiple minor loci are required for full susceptibility, and confirm a critical genetic dependence on CD4 T(H)-cell differentiation and function in the pathogenesis of both diseases.

Signal regulatory protein α regulates the homeostasis of T lymphocytes in the spleen

The molecular basis for formation of lymphoid follicle and its homeostasis in the secondary lymphoid organs remains unclear. Signal regulatory protein α (SIRPα), an Ig superfamily protein that is predominantly expressed in dendritic cells or macrophages, mediates cell-cell signaling by interacting with CD47, another Ig superfamily protein. In this study, we show that the size of the T cell zone as well as the number of CD4(+) T cells were markedly reduced in the spleen of mice bearing a mutant (MT) SIRPα that lacks the cytoplasmic region compared with those of wild-type mice. In addition, the expression of CCL19 and CCL21, as well as of IL-7, which are thought to be important for development or homeostasis of the T cell zone, was markedly decreased in the spleen of SIRPα MT mice. By the use of bone marrow chimera, we found that hematopoietic SIRPα is important for development of the T cell zone as well as the expression of CCL19 and CCL21 in the spleen. The expression of lymphotoxin and its receptor, lymphotoxin β receptor, as well as the in vivo response to lymphotoxin β receptor stimulation were also decreased in the spleen of SIRPα MT mice. CD47-deficient mice also manifested phenotypes similar to SIRPα MT mice. These data suggest that SIRPα as well as its ligand CD47 are thus essential for steady-state homeostasis of T cells in the spleen.

LIGHT (TNFSF14) inhibits adipose differentiation without affecting adipocyte metabolism

OBJECTIVE

The member of the tumor necrosis factor family LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for herpesvirus entry on T cells; TNFSF14 (tumor necrosis factor super family protein 14) is primarily expressed in lymphocytes, in which it induces the expression of pro-inflammatory cytokines and alterations of lipid homeostasis. Recently, the protein was shown to be upregulated in obesity and to induce cytokine secretion from adipocytes.

RESEARCH METHODS AND PROCEDURES

Using an automated complementary DNA (cDNA) screen, LIGHT was identified to inhibit adipose differentiation. As cellular models for adipogenesis mouse 3T3-L1, human SGBS (Simpson-Golabi-Behmel syndrome) and primary human preadipocytes differentiated in vitro were used as well as primary human adipocytes to study adipocyte functions. Analysis of lipid deposition by Oil Red O staining, mRNA expression by quantitative reverse transcriptase-PCR, nuclear factor (NF)-κB activation as well as protein secretion by enzyme linked immunosorbent assay and Luminex technology was performed.

RESULTS

LIGHT was found to inhibit lipid accumulation in the three models of preadipocytes in a dose-dependent manner without cytotoxic effects. This inhibition of differentiation was probably because of interference at early steps of adipogenesis, as early exposure during differentiation showed the strongest effect, as assessed by decreased peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer-binding protein-α (C/EBPα) mRNA expression. In contrast to TNFα, basal and insulin-stimulated glucose uptake and lipolysis of terminally differentiated mature adipocytes were not altered in the presence of LIGHT. At a concentration sufficient to inhibit differentiation, secretion of proinflammatory cytokines was not significantly induced and NF-κB activity was only modestly induced compared with TNFα.

CONCLUSION

LIGHT is a novel inhibitor of human adipocyte differentiation without adversely influencing central metabolic pathways in adipocytes.

Lymphotoxin beta receptor signaling in intestinal epithelial cells orchestrates innate immune responses against mucosal bacterial infection

Epithelial cells provide the first line of defense against mucosal pathogens; however, their coordination with innate and adaptive immune cells is not well understood. Using mice with conditional gene deficiencies, we found that lymphotoxin (LT) from innate cells expressing transcription factor RORgammat, but not from adaptive T and B cells, was essential for the control of mucosal C. rodentium infection. We demonstrate that the LTbetaR signaling was required for the regulation of the early innate response against infection. Furthermore, we have revealed that LTbetaR signals in gut epithelial cells and hematopoietic-derived cells coordinate to protect the host from infection. We further determined that LTbetaR signaling in intestinal epithelial cells was required for recruitment of neutrophils to the infection site early during infection via production of CXCL1 and CXCL2 chemokines. These results support a model wherein LT from RORgammat(+) cells orchestrates the innate immune response against mucosal microbial infection.

LIGHT protein suppresses tumor growth by augmentation of immune response

The tumor necrosis factor (TNF) superfamily member LIGHT has potent anti-tumor activities through activation of the immune response, and it is a promising candidate for use in cancer immunotherapy. However, there are no reports of the anti-tumor effects of LIGHT protein in vivo because of the lack of easy, efficient methods of manufacturing this protein. Here, we developed a method of manufacturing recombinant LIGHT protein using Escherichia coli through refolding of inclusion bodies; we then evaluated the anti-tumor activity of the protein. LIGHT protein expressed in E. coli showed the same biological activities and binding affinities to its receptors as did LIGHT expressed in mammalian cells. In addition, intratumoral injection of LIGHT significantly suppressed tumor growth, with augmentation of antigen-specific IFN-gamma-producing cells in the regional lymph nodes and spleen. These results indicate that LIGHT protein efficiently evokes the systemic tumor-specific immune response, and thus induces tumor suppression.