Lymphotoxin in physiology of lymphoid tissues - Implication for antiviral defense

LTβR-RelB signaling in intestinal epithelial cells protects from chemotherapy-induced mucosal damage

The intricate immune mechanisms governing mucosal healing following intestinal damage induced by cytotoxic drugs remain poorly understood. The goal of this study was to investigate the role of lymphotoxin beta receptor (LTβR) signaling in chemotherapy-induced intestinal damage. LTβR deficient mice exhibited heightened body weight loss, exacerbated intestinal pathology, increased proinflammatory cytokine expression, reduced IL-22 expression, and proliferation of intestinal epithelial cells following methotrexate (MTX) treatment. Furthermore, LTβR-/-IL-22-/- mice succumbed to MTX treatment, suggesting that LTβR- and IL-22- dependent pathways jointly promote mucosal repair. Although both LTβR ligands LIGHT and LTβ were upregulated in the intestine early after MTX treatment, LIGHT-/- mice, but not LTβ-/- mice, displayed exacerbated disease. Further, we revealed the critical role of T cells in mucosal repair as T cell-deficient mice failed to upregulate intestinal LIGHT expression and exhibited increased body weight loss and intestinal pathology. Analysis of mice with conditional inactivation of LTβR revealed that LTβR signaling in intestinal epithelial cells, but not in Lgr5+ intestinal stem cells, macrophages or dendritic cells was critical for mucosal repair. Furthermore, inactivation of the non-canonical NF-kB pathway member RelB in intestinal epithelial cells promoted MTX-induced disease. Based on these results, we propose a model wherein LIGHT produced by T cells activates LTβR-RelB signaling in intestinal epithelial cells to facilitate mucosal repair following chemotherapy treatment.

Joint association of air pollution exposure and inflammation-related proteins in relation to infant lung function

BACKGROUND AND AIM

Systemic inflammation is one potential mechanism underlying negative impact of air pollution on lung function. Levels of inflammation-related proteins have the potential to characterize infants' susceptibility to air pollution induced lung function impairment. This study aimed to examine the interplay between air pollution exposure and inflammation-related proteins on lung function in 6-months-old infants.

METHODS

In the EMIL birth cohort from Stockholm (n = 82), dynamic spirometry, along with measurement of plasma levels of 92 systemic inflammation-related proteins (Olink Proseek Multiplex Inflammation panel) have been carried out in infants aged six months. Time-weighted average exposure to particles with an aerodynamic diameter of <10 μm (PM10), <2.5 μm (PM2.5), and nitrogen dioxide (NO2) at residential addresses from birth and onwards was estimated via validated dispersion models. To characterize the abnormality of inflammation-related protein profile, for each protein in each infant, we calculated the relative deviance of the protein level from age- and sex-specific median in terms of its age- and sex-specific interquartile range (IQR), followed by computing the absolute value of the smallest relative deviance, "minimum absolute deviance". Using linear regression models, interaction of air pollution and the abnormal inflammatory profile on lung function was estimated on the additive scale.

RESULTS

We found joint association of PM exposure and an abnormal inflammatory protein profile in relation to FEV0.5 and FVC. For 0.1 unit increase in minimum absolute deviance, one IQR increase in PM10 was associated with 85.9 ml (95% CI: -122.9, -48.9) additional decrease in FEV0.5, and 72.3 ml (95% CI: -121.5, -23.2) additional decrease in FVC. Similar results were obtained with PM2.5 exposure, while less apparent for NO2.

CONCLUSIONS

Early life air pollution exposure and abnormal inflammation-related protein profiles may interact synergistically towards lower lung function in infants.

The murine meninges acquire lymphoid tissue properties and harbour autoreactive B cells during chronic Trypanosoma brucei infection

The meningeal space is a critical brain structure providing immunosurveillance for the central nervous system (CNS), but the impact of infections on the meningeal immune landscape is far from being fully understood. The extracellular protozoan parasite Trypanosoma brucei, which causes human African trypanosomiasis (HAT) or sleeping sickness, accumulates in the meningeal spaces, ultimately inducing severe meningitis and resulting in death if left untreated. Thus, sleeping sickness represents an attractive model to study immunological dynamics in the meninges during infection. Here, by combining single-cell transcriptomics and mass cytometry by time-of-flight (CyTOF) with in vivo interventions, we found that chronic T. brucei infection triggers the development of ectopic lymphoid aggregates (ELAs) in the murine meninges. These infection-induced ELAs were defined by the presence of ER-TR7+ fibroblastic reticular cells, CD21/35+ follicular dendritic cells (FDCs), CXCR5+ PD1+ T follicular helper-like phenotype, GL7+ CD95+ GC-like B cells, and plasmablasts/plasma cells. Furthermore, the B cells found in the infected meninges produced high-affinity autoantibodies able to recognise mouse brain antigens, in a process dependent on LTβ signalling. A mid-throughput screening identified several host factors recognised by these autoantibodies, including myelin basic protein (MBP), coinciding with cortical demyelination and brain pathology. In humans, we identified the presence of autoreactive IgG antibodies in the cerebrospinal fluid (CSF) of second stage HAT patients that recognised human brain lysates and MBP, consistent with our findings in experimental infections. Lastly, we found that the pathological B cell responses we observed in the meninges required the presence of T. brucei in the CNS, as suramin treatment before the onset of the CNS stage prevented the accumulation of GL7+ CD95+ GC-like B cells and brain-specific autoantibody deposition. Taken together, our data provide evidence that the meningeal immune response during chronic T. brucei infection results in the acquisition of lymphoid tissue-like properties, broadening our understanding of meningeal immunity in the context of chronic infections. These findings have wider implications for understanding the mechanisms underlying the formation ELAs during chronic inflammation resulting in autoimmunity in mice and humans, as observed in other autoimmune neurodegenerative disorders, including neuropsychiatric lupus and multiple sclerosis.

Past, Present and (Foreseeable) Future of Biological Anti-TNF Alpha Therapy

Due to the key role of tumor necrosis factor-alpha (TNF-α) in the pathogenesis of immunoinflammatory diseases, TNF-α inhibitors have been successfully developed and used in the clinical treatment of autoimmune disorders. Currently, five anti-TNF-α drugs have been approved: infliximab, adalimumab, golimumab, certolizumab pegol and etanercept. Anti-TNF-α biosimilars are also available for clinical use. Here, we will review the historical development as well as the present and potential future applications of anti-TNF-α therapies, which have led to major improvements for patients with several autoimmune diseases, such as rheumatoid arthritis (RA), ankylosing spondylitis (AS), Crohn's disease (CD), ulcerative colitis (UC), psoriasis (PS) and chronic endogenous uveitis. Other therapeutic areas are under evaluation, including viral infections, e.g., COVID-19, as well as chronic neuropsychiatric disorders and certain forms of cancer. The search for biomarkers able to predict responsiveness to anti-TNF-α drugs is also discussed.

Predictive Value of Inflammatory Cytokines in Early Pregnancy for Liver Dysfunction in Pregnant Women with Hepatitis B

The purpose of this study is to explore the predictive value of cytokine levels in the first trimester of pregnancy on abnormal liver function of pregnant women with hepatitis B in the third trimester of pregnancy. A total of 111 pregnant women with HBV infection at 12 weeks gestation participated in the study. The levels of IL-6, IL-8, TNF-α in peripheral blood of the patients and liver function indexes were detected. Subsequently, the pregnant women were followed up, and the liver function was detected at 36 weeks of gestation. According to liver function indexes, patients were divided into normal liver function group and abnormal liver function group to determine the correlation between cytokines in early pregnancy and abnormal liver function in late pregnancy. Kaplan-Meier survival curve and multivariate Cox analysis were used to evaluate the predictive value of cytokines for liver dysfunction. At 12 weeks of gestation, cytokine levels in the normal liver function group were significantly lower than that in the abnormal liver function group. Kaplan-Meier survival analysis showed that the increased IL-6 level was associated with abnormal liver function in late pregnancy. Multivariate Cox regression analysis revealed that IL-6 level was an independent predictor of abnormal liver function in patients with normal liver function in the late pregnancy. The high expression level of cytokine IL-6 at 12 weeks of pregnancy has noteworthy predictive significance for the abnormal liver function of hepatitis B pregnant women in third trimester of pregnancy.

The dynamic changes and sex differences of 147 immune-related proteins during acute COVID-19 in 580 individuals

INTRODUCTION

Severe COVID-19 leads to important changes in circulating immune-related proteins. To date it has been difficult to understand their temporal relationship and identify cytokines that are drivers of severe COVID-19 outcomes and underlie differences in outcomes between sexes. Here, we measured 147 immune-related proteins during acute COVID-19 to investigate these questions.

METHODS

We measured circulating protein abundances using the SOMAscan nucleic acid aptamer panel in two large independent hospital-based COVID-19 cohorts in Canada and the United States. We fit generalized additive models with cubic splines from the start of symptom onset to identify protein levels over the first 14 days of infection which were different between severe cases and controls, adjusting for age and sex. Severe cases were defined as individuals with COVID-19 requiring invasive or non-invasive mechanical respiratory support.

RESULTS

580 individuals were included in the analysis. Mean subject age was 64.3 (sd 18.1), and 47% were male. Of the 147 proteins, 69 showed a significant difference between cases and controls (p < 3.4 × 10-4). Three clusters were formed by 108 highly correlated proteins that replicated in both cohorts, making it difficult to determine which proteins have a true causal effect on severe COVID-19. Six proteins showed sex differences in levels over time, of which 3 were also associated with severe COVID-19: CCL26, IL1RL2, and IL3RA, providing insights to better understand the marked differences in outcomes by sex.

CONCLUSIONS

Severe COVID-19 is associated with large changes in 69 immune-related proteins. Further, five proteins were associated with sex differences in outcomes. These results provide direct insights into immune-related proteins that are strongly influenced by severe COVID-19 infection.

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.

LTα, TNF, and ILC3 in Peyer's Patch Organogenesis

TNF and LTα are structurally related cytokines of the TNF superfamily. Their genes are located in close proximity to each other and to the Ltb gene within the TNF/LT locus inside MHC. Unlike Ltb, transcription of Tnf and of Lta is tightly controlled, with the Tnf gene being an immediate early gene that is rapidly induced in response to various inflammatory stimuli. Genes of the TNF/LT locus play a crucial role in lymphoid tissue organogenesis, although some aspects of their specific contribution remain controversial. Here, we present new findings and discuss the distinct contribution of TNF produced by ILC3 cells to Peyer’s patch organogenesis.

Attenuated activation of pulmonary immune cells in mRNA-1273-vaccinated hamsters after SARS-CoV-2 infection

The mRNA-1273 vaccine is effective against SARS-CoV-2 and was granted emergency use authorization by the FDA. Clinical studies, however, cannot provide the controlled response to infection and complex immunological insight that are only possible with preclinical studies. Hamsters are the only model that reliably exhibits severe SARS-CoV-2 disease similar to that in hospitalized patients, making them pertinent for vaccine evaluation. We demonstrate that prime or prime-boost administration of mRNA-1273 in hamsters elicited robust neutralizing antibodies, ameliorated weight loss, suppressed SARS-CoV-2 replication in the airways, and better protected against disease at the highest prime-boost dose. Unlike in mice and nonhuman primates, low-level virus replication in mRNA-1273-vaccinated hamsters coincided with an anamnestic response. Single-cell RNA sequencing of lung tissue permitted high-resolution analysis that is not possible in vaccinated humans. mRNA-1273 prevented inflammatory cell infiltration and the reduction of lymphocyte proportions, but enabled antiviral responses conducive to lung homeostasis. Surprisingly, infection triggered transcriptome programs in some types of immune cells from vaccinated hamsters that were shared, albeit attenuated, with mock-vaccinated hamsters. Our results support the use of mRNA-1273 in a 2-dose schedule and provide insight into the potential responses within the lungs of vaccinated humans who are exposed to SARS-CoV-2.

Lymphotoxin: from the physiology to the regeneration of the thymic function

The members of the Tumor Necrosis Factor (TNF) superfamily, the ligand lymphotoxin α1β2 (LTα1β2) and its unique receptor lymphotoxin β receptor (LTβR), play a pivotal role in the establishment and regulation of the immune system by allowing a tight communication between lymphocytes and stromal cells. Recent advances using transgenic mice harboring a specific deletion of the Ltbr gene in distinct stromal cells have revealed important roles for LTβR signaling in the thymic function that ensures the generation of a diverse and self-tolerant T-cell repertoire. In this review, we summarize our current knowledge on this signaling axis in the thymic homing of lymphoid progenitors and peripheral antigen-presenting cells, the trafficking and egress of thymocytes, the differentiation of medullary thymic epithelial cells, and the establishment of central tolerance. We also highlight the importance of LTα1β2/LTβR axis in controlling the recovery of the thymic function after myeloablative conditioning regimen, opening novel perspectives in regenerative medicine.

AP-1 family transcription factors: a diverse family of proteins that regulate varied cellular activities in classical hodgkin lymphoma and ALK+ ALCL

Classical Hodgkin lymphoma (cHL) and anaplastic lymphoma kinase-positive, anaplastic large cell lymphoma (ALK+ ALCL) are B and T cell lymphomas respectively, which express the tumour necrosis factor receptor superfamily member, CD30. Another feature shared by cHL and ALK+ ALCL is the aberrant expression of multiple members of the activator protein-1 (AP-1) family of transcription factors which includes proteins of the Jun, Fos, ATF, and Maf subfamilies. In this review, we highlight the varied roles these proteins play in the pathobiology of these lymphomas including promoting proliferation, suppressing apoptosis, and evading the host immune response. In addition, we discuss factors contributing to the elevated expression of these transcription factors in cHL and ALK+ ALCL. Finally, we examine therapeutic strategies for these lymphomas that exploit AP-1 transcriptional targets or the signalling pathways they regulate.

Identification of a Distal Locus Enhancer Element That Controls Cell Type-Specific TNF and LTA Gene Expression in Human T Cells

The human TNF/LT locus genes TNF, LTA, and LTB are expressed in a cell type-specific manner. In this study, we show that a highly conserved NFAT binding site within the distal noncoding element hHS-8 coordinately controls TNF and LTA gene expression in human T cells. Upon activation of primary human CD4⁺ T cells, hHS-8 and the TNF and LTA promoters display increased H3K27 acetylation and nuclease sensitivity and coordinate induction of TNF, LTA, and hHS-8 enhancer RNA transcription occurs. Functional analyses using CRISPR/dead(d)Cas9 targeting of the hHS-8-NFAT site in the human T cell line CEM demonstrate significant reduction of TNF and LTA mRNA synthesis and of RNA polymerase II recruitment to their promoters. These studies elucidate how a distal element regulates the inducible cell type-specific gene expression program of the human TNF/LT locus and provide an approach for modulation of TNF and LTA transcription in human disease using CRISPR/dCas9.

Mechanisms of lymphatic system-specific viral replication and its potential role in autoimmune disease

Viral infections can be fatal because of the direct cytopathic effects of the virus or the induction of a strong, uncontrolled inflammatory response. Virus and host intrinsic characteristics strongly modulate the outcome of viral infections. Recently we determined the circumstances under which enhanced replication of virus within the lymphoid tissue is beneficial for the outcome of a disease. This enforced viral replication promotes anti-viral immune activation and, counterintuitively, accelerates virus control. In this review we summarize the mechanisms that contribute to enforced viral replication. Antigen-presenting cells and CD169⁺ macrophages exhibit enforced viral replication after infection with the model viruses lymphocytic choriomeningitis virus (LCMV) and vesicular stomatitis virus (VSV). Ubiquitin-specific peptidase 18 (Usp18), an endogenous type I interferon blocker in CD169⁺ macrophages, has been identified as a proviral gene, as are B cell activating factor (BAFF) and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). Lymphotoxins (LT) strongly enhance viral replication in the spleen and lymph nodes. All these factors modulate splenic architecture and thereby promote the development of CD169⁺ macrophages. Tumor necrosis factor alpha (TNF-α) and nuclear factor kappa-light-chain-enhancer of activated B cell signaling (NF-κB) have been found to promote the survival of infected CD169⁺ macrophages, thereby similarly promoting enforced viral replication. Association of autoimmune disease with infections is evident from (1) autoimmune phenomena described during a chronic virus infection; (2) onset of autoimmune disease simultaneous to viral infections; and (3) experimental evidence. Involvement of virus infection during onset of type I diabetes is strongly evident. Epstein-Bar virus (EBV) infection was discussed to be involved in the pathogenesis of systemic lupus erythematosus. In conclusion, several mechanisms promote viral replication in secondary lymphatic organs. Identifying such factors in humans is a challenge for future studies.

Different origins of paralogues of salmonid TNR1 and TNFR2: Characterisation and expression analysis of four TNF receptor genes in rainbow trout Oncorhynchus mykiss

Mammalian TNFR1 and TNFR2 bind TNFα and TNFβ, and provide key communication signals to a variety of cell types during development and immune responses that are crucial for cell survival, proliferation and apoptosis. In teleost fish TNFβ is absent but TNFα has been expanded by the third whole genome duplication (3R WGD) and again by a 4R WGD in some lineages, leading to the four TNFα paralogues known in salmonids. Two paralogues for each of TNFR1 and TNFR2 have been cloned in rainbow trout in this study and are present in other salmonid genomes. Whilst the TNFR2 paralogues were generated via the 4R salmonid WGD, the TNFR1 paralogues arose from a local en bloc duplication. Functional diversification of TNFR paralogues was evidenced by differential gene expression and modulation, upstream ATGs affecting translation, ATTTA motifs in the 3'-UTR regulating mRNA stability, and post-translational modification by N-glycosylation. Trout TNFR are highly expressed in immune tissues/organs, and other tissues, in a gene- and tissue-specific manner. Furthermore, their expression is differentially modulated by PAMPs and cytokines in a cell type- and stimulant-specific manner. Such findings suggest an important role of the TNF/TNFR axis in the immune response and other physiological processes in fish.

Microbial Agents as Putative Inducers of B Cell Lymphoma in Sjögren's Syndrome through an Impaired Epigenetic Control: The State-of-The-Art

Introduction

Understanding the mechanisms underlying the pathogenesis of Sjögren's syndrome (SS) is crucially important in order to be able to discriminate the steps that lead to B cell transformation and promptly identify the patients at risk of lymphomagenesis. The aim of this narrative review is to describe the evidence concerning the role that infections or dysbiosis plays in the epigenetic control of gene expression in SS patients and their possible involvement in B cell lymphomagenesis.

Materials and Methods

We searched the PubMed and Google Scholar databases and selected a total of 92 articles published during the last 25 years that describe experimental and clinical studies of the potential associations of microbiota and epigenetic aberrations with the risk of B cell lymphoma in SS patients.

Results and Discussion

The genetic background of SS patients is characterized by the hyperexpression of genes that are mainly involved in regulating the innate and adaptive immune responses and oncogenesis. In addition, salivary gland epithelial cells and lymphocytes both have an altered epigenetic background that enhances the activation of proinflammatory and survival pathways. Dysbiosis or chronic latent infections may tune the immune response and modify the cell epigenetic machinery in such a way as to give B lymphocytes an activated or transformed phenotype. It is also worth noting that transposable integrated retroelements may participate in the pathogenesis of SS and B cell lymphomagenesis by inducing DNA breaks, modulating cell gene expression, or generating aberrant transcripts that chronically stimulate the immune system.

Conclusions

Microorganisms may epigenetically modify target cells and induce their transcriptome to generate an activated or transformed phenotype. The occurrence of lymphoma in more than 15% of SS patients may be the end result of a combination of genetics, epigenetics, and dysbiosis or latent infections.

Growth of Murine Splenic Tissue Is Suppressed by Lymphotoxin β-Receptor Signaling (LTβR) Originating from Splenic and Non-Splenic Tissues

Development and maintenance of secondary lymphoid organs such as lymph nodes and spleen essentially depend on lymphotoxin β-receptor (LTβR) signaling. It is unclear, however, by which molecular mechanism their size is limited. Here, we investigate whether the LTβR pathway is also growth suppressing. By using splenic tissue transplantation it is possible to analyze a potential contribution of LTβR signaling inside and outside of the implanted tissue. We show that LTβR signaling within the endogenous spleen and within non-splenic tissues both significantly suppressed the regeneration of implanted splenic tissue. The suppressive activity positively correlated with the total number of LTβR expressing cells in the animal (regenerate weights of 115 ± 8 mg in LTβR deficient recipients and of 12 ± 9 mg in wild-type recipients), affected also developed splenic tissue, and was induced but not executed via LTβR signaling. Two-dimensional differential gel electrophoresis and subsequent mass spectrometry of stromal splenic tissue was applied to screen for potential factors mediating the LTβR dependent suppressive activity. Thus, LTβR dependent growth suppression is involved in regulating the size of secondary lymphoid organs, and might be therapeutically used to eradicate tertiary lymphoid tissues during autoimmune diseases.