Tertiary Lymphoid Structures: Diversity in Their Development, Composition, and Role

Tertiary lymphoid tissues: a regional hub for kidney inflammation

Tertiary lymphoid tissues (TLTs) are inducible ectopic lymphoid tissues that develop at sites of chronic inflammation in nonlymphoid organs. As with lymph nodes, TLTs initiate adaptive immune responses and coordinate local tissue immunity. Although virtually ignored for decades, TLTs have recently received a great deal of attention for their ability to influence disease severity, prognosis and response to therapy in various diseases, including cancer, autoimmune disorders and infections. TLTs are also induced in kidneys of patients with chronic kidney diseases such as immunoglobulin A nephropathy and lupus nephritis. Nevertheless, TLTs in the kidney have not been extensively investigated and their mechanism of development, functions and clinical relevance remain unknown, mainly because of the absence of adequate murine kidney TLT models and limited availability of human kidney samples containing TLTs. We recently found that aged kidneys, but not young kidneys, exhibit multiple TLTs after injury. Interestingly, although they are a minor component of TLTs, resident fibroblasts in the kidneys diversify into several distinct phenotypes that play crucial roles in TLT formation. Furthermore, the potential of TLTs as a novel kidney injury/inflammation marker as well as a novel therapeutic target for kidney diseases is also suggested. In this review article we describe the current understanding of TLTs with a focus on age-dependent TLTs in the kidney and discuss their potential as a novel therapeutic target and kidney inflammation marker.

Immunology of Giant Cell Arteritis

Giant cell arteritis is an autoimmune disease of medium and large arteries, characterized by granulomatous inflammation of the three-layered vessel wall that results in vaso-occlusion, wall dissection, and aneurysm formation. The immunopathogenesis of giant cell arteritis is an accumulative process in which a prolonged asymptomatic period is followed by uncontrolled innate immunity, a breakdown in self-tolerance, the transition of autoimmunity from the periphery into the vessel wall and, eventually, the progressive evolution of vessel wall inflammation. Each of the steps in pathogenesis corresponds to specific immuno-phenotypes that provide mechanistic insights into how the immune system attacks and damages blood vessels. Clinically evident disease begins with inappropriate activation of myeloid cells triggering the release of hepatic acute phase proteins and inducing extravascular manifestations, such as muscle pains and stiffness diagnosed as polymyalgia rheumatica. Loss of self-tolerance in the adaptive immune system is linked to aberrant signaling in the NOTCH pathway, leading to expansion of NOTCH1+CD4+ T cells and the functional decline of NOTCH4+ T regulatory cells (Checkpoint 1). A defect in the endothelial cell barrier of adventitial vasa vasorum networks marks Checkpoint 2; the invasion of monocytes, macrophages and T cells into the arterial wall. Due to the failure of the immuno-inhibitory PD-1 (programmed cell death protein 1)/PD-L1 (programmed cell death ligand 1) pathway, wall-infiltrating immune cells arrive in a permissive tissues microenvironment, where multiple T cell effector lineages thrive, shift toward high glycolytic activity, and support the development of tissue-damaging macrophages, including multinucleated giant cells (Checkpoint 3). Eventually, the vascular lesions are occupied by self-renewing T cells that provide autonomy to the disease process and limit the therapeutic effectiveness of currently used immunosuppressants. The multi-step process deviating protective to pathogenic immunity offers an array of interception points that provide opportunities for the prevention and therapeutic management of this devastating autoimmune disease.

Tertiary Lymphoid Structures, Immune Response, and Prognostic Relevance in Non-Small Cell Lung Cancer

We assessed the presence of 'tertiary lymphoid structures' (TLS) in a series of surgically treated non-small cell lung carcinomas (NSCLC). The TLS-density in the tumor periphery (pTLS) ranged from 0 to 1.8 (median 0.45), while in inner tumor areas (iTLS) ranged from 0 to 1.0 (median 0); (p < 0.0001). High pTLS-density was linked with early stage of the disease. Glycolysis-related enzyme expression (MCT1, Hexokinase 2) was linked with high pTLS-density (p < 0.05). High pTLS and iTLS densities were linked with better postoperative prognosis (p = 0.02 and p = 0.01, respectively). Assessment of TLS is a useful prognostic marker in NSCLC.

Cancer immunotherapies transition endothelial cells into HEVs that generate TCF1+ T lymphocyte niches through a feed-forward loop

The lack of T cell infiltrates is a major obstacle to effective immunotherapy in cancer. Conversely, the formation of tumor-associated tertiary-lymphoid-like structures (TA-TLLSs), which are the local site of humoral and cellular immune responses against cancers, is associated with good prognosis, and they have recently been detected in immune checkpoint blockade (ICB)-responding patients. However, how these lymphoid aggregates develop remains poorly understood. By employing single-cell transcriptomics, endothelial fate mapping, and functional multiplex immune profiling, we demonstrate that antiangiogenic immune-modulating therapies evoke transdifferentiation of postcapillary venules into inflamed high-endothelial venules (HEVs) via lymphotoxin/lymphotoxin beta receptor (LT/LTβR) signaling. In turn, tumor HEVs boost intratumoral lymphocyte influx and foster permissive lymphocyte niches for PD1^- and PD1⁺TCF1⁺ CD8 T cell progenitors that differentiate into GrzB⁺PD1⁺ CD8 T effector cells. Tumor-HEVs require continuous CD8 and NK cell-derived signals revealing that tumor HEV maintenance is actively sculpted by the adaptive immune system through a feed-forward loop.

Sterol O-Acyltransferase Inhibition Ameliorates High-Fat Diet-Induced Renal Fibrosis and Tertiary Lymphoid Tissue Maturation after Ischemic Reperfusion Injury

Metabolic syndrome is associated with the development of chronic kidney disease (CKD). We previously demonstrated that aged kidneys are prone to developing tertiary lymphoid tissues (TLTs) and sustain inflammation after injury, leading to CKD progression; however, the relationship between renal TLT and metabolic syndrome is unknown. In this study, we demonstrated that a high-fat diet (HFD) promoted renal TLT formation and inflammation via sterol O-acyltransferase (SOAT) 1-dependent mechanism. Mice fed a HFD prior to ischemic reperfusion injury (IRI) exhibited pronounced renal TLT formation and sustained inflammation compared to the controls. Untargeted lipidomics revealed the increased levels of cholesteryl esters (CEs) in aged kidneys with TLT formation after IRI, and, consistently, the Soat1 gene expression increased. Treatment with avasimibe, a SOAT inhibitor, attenuated TLT maturation and renal inflammation in HFD-fed mice subjected to IRI. Our findings suggest the importance of SOAT1-dependent CE accumulation in the pathophysiology of CKDs associated with TLT.

Conjunctiva Resident γδ T Cells Expressed High Level of IL-17A and Promoted the Severity of Dry Eye

Purpose

Conjunctival inflammation promotes ocular surface disorders in dry eye disease (DED). Here we identified γδ T cells as the predominant source of IL-17A in the murine conjunctiva and assessed their contribution to the pathogenesis of DED.

Methods

We enrolled 22 patients with DED, and analyzed the proportion of γδ T cells in the conjunctival epithelial samples by flow cytometry. Adult C57Bl/6 wild-type and TCRδ^−/− mice were used to induce DED models to investigate the role of γδ T cells. The characteristics of immune cell infiltration and the expression of immune-related cytokines or markers in mouse conjunctiva were analyzed by flow cytometry, Western blot, and quantitative polymerase chain reaction.

Results

The proportion of γδ T cells in the human DED conjunctiva is significantly higher in patients with severe corneal epithelial defects than in mild ones, which is consistently observed in the murine DED model. Further, a high level of IL-17A but not IFN-γ is detected in the conjunctiva of mice. The increased murine IL-17A–producing cells on the conjunctiva are identified as γδ T cells predominantly and Th17 cells to a lesser extent. Ablation of γδ T cells by antibody depletion or genetic deletion of TCRδ alleviates ocular surface damage in the murine DED model.

Conclusions

Our studies evaluate human and experimental murine DED for evidence of γδ T-cell–mediated inflammation and highlight a potential therapeutic synergy by targeting IL-17 and γδ T cells in DED treatment.

The Role of Interleukin-7 in the Formation of Tertiary Lymphoid Structures and Their Prognostic Value in Gastrointestinal Cancers

Immunotherapies for the treatment of solid tumors continue to develop in preclinical and clinical research settings. Unfortunately, for many patients the tumor fails to respond or becomes resistant to therapies such as checkpoint inhibitors (CPIs) targeting programmed cell death protein-1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen-4 (CTLA-4). In many cancers, failed response to CPIs can be attributed to poor T cell infiltration, dominant immunosuppression, and exhausted immune responses. In gastrointestinal (GI) cancers T cell infiltration can be dismal, with several reports finding that CD8⁺ T cells compose less than 2% of all cells within the tumor. Organized aggregates of lymphocytes, antigen-presenting cells, and vessels, together termed tertiary lymphoid structures (TLSs), are hypothesized to be a major source of T cells within solid tumors. The intratumoral formation of these organized immune centers appears to rely on intricate cytokine and chemokine signaling to heterogeneous cell populations such as B and T cells, innate lymphoid cells, fibroblasts, and dendritic cells. In GI cancers, the presence and density of TLSs provide prognostic value for predicting outcome and survival. Further, TLS presence and density associates with favorable responses to CPIs in many cancers. This review highlights the prognostic value of TLSs in GI cancers, the role of the homeostatic cytokine interleukin-7 (IL-7) in TLS formation, and the induction of TLSs in solid tumors by novel therapeutics.

Molecular pathogenesis, targeted therapies, and future perspectives for gastric cancer

Gastric cancer is a major source of global cancer mortality with limited treatment options and poor patient survival. As our molecular understanding of gastric cancer improves, we are now beginning to recognize that these cancers are a heterogeneous group of diseases with incredibly unique pathogeneses and active oncogenic pathways. It is this molecular diversity and oftentimes lack of common oncogenic driver mutations that bestow the poor treatment responses that oncologists often face when treating gastric cancer. In this review, we will examine the treatments for gastric cancer including up-to-date molecularly targeted therapies and immunotherapies. We will then review the molecular subtypes of gastric cancer to highlight the diversity seen in this disease. We will then shift our discussion to basic science and gastric cancer mouse models as tools to study gastric cancer molecular heterogeneity. Furthermore, we will elaborate on a molecular process termed paligenosis and the cyclical hit model as key events during gastric cancer initiation that impart nondividing mature differentiated cells the ability to re-enter the cell cycle and accumulate disparate genomic mutations during years of chronic inflammation and injury. As our basic science understanding of gastric cancer advances, so too must our translational and clinical efforts. We will end with a discussion regarding single-cell molecular analyses and cancer organoid technologies as future translational avenues to advance our understanding of gastric cancer heterogeneity and to design precision-based gastric cancer treatments. Elucidation of interpatient and intratumor heterogeneity is the only way to advance future cancer prevention, diagnoses and treatment.

Tertiary lymphoid structures accompanied by fibrillary matrix morphology impact anti-tumor immunity in basal cell carcinomas

Tertiary lymphoid structures (TLS) are specialized lymphoid formations that serve as local repertoire of T- and B-cells at sites of chronic inflammation, autoimmunity, and cancer. While presence of TLS has been associated with improved response to immune checkpoint blockade therapies and overall outcomes in several cancers, its prognostic value in basal cell carcinoma (BCC) has not been investigated. Herein, we determined the prognostic impact of TLS by relating its prevalence and maturation with outcome measures of anti-tumor immunity, namely tumor infiltrating lymphocytes (TILs) and tumor killing. In 30 distinct BCCs, we show the presence of TLS was significantly enriched in tumors harboring a nodular component and more mature primary TLS was associated with TIL counts. Moreover, assessment of the fibrillary matrix surrounding tumors showed discrete morphologies significantly associated with higher TIL counts, critically accounting for heterogeneity in TIL count distribution within TLS maturation stages. Specifically, increased length of fibers and lacunarity of the matrix with concomitant reduction in density and alignment of fibers were present surrounding tumors displaying high TIL counts. Given the interest in inducing TLS formation as a therapeutic intervention as well as its documented prognostic value, elucidating potential impediments to the ability of TLS in driving anti-tumor immunity within the tumor microenvironment warrants further investigation. These results begin to address and highlight the need to integrate stromal features which may present a hindrance to TLS formation and/or effective function as a mediator of immunotherapy response.

Aberrant B Cell Signaling in Autoimmune Diseases

Aberrant B cell signaling plays a critical in role in various systemic and organ-specific autoimmune diseases. This is supported by genetic evidence by many functional studies in B cells from patients or specific animal models and by the observed efficacy of small-molecule inhibitors. In this review, we first discuss key signal transduction pathways downstream of the B cell receptor (BCR) that ensure that autoreactive B cells are removed from the repertoire or functionally silenced. We provide an overview of aberrant BCR signaling that is associated with inappropriate B cell repertoire selection and activation or survival of peripheral B cell populations and plasma cells, finally leading to autoantibody formation. Next to BCR signaling, abnormalities in other signal transduction pathways have been implicated in autoimmune disease. These include reduced activity of several phosphates that are downstream of co-inhibitory receptors on B cells and increased levels of BAFF and APRIL, which support survival of B cells and plasma cells. Importantly, pathogenic synergy of the BCR and Toll-like receptors (TLR), which can be activated by endogenous ligands, such as self-nucleic acids, has been shown to enhance autoimmunity. Finally, we will briefly discuss therapeutic strategies for autoimmune disease based on interfering with signal transduction in B cells.

Beta cell and immune cell interactions in autoimmune type 1 diabetes: How they meet and talk to each other

Background

Scope of review

Major conclusions

Tumour-infiltrating B cells: immunological mechanisms, clinical impact and therapeutic opportunities

Although immunotherapy research to date has focused largely on T cells, there is mounting evidence that tumour-infiltrating B cells and plasma cells (collectively referred to as tumour-infiltrating B lymphocytes (TIL-Bs)) have a crucial, synergistic role in tumour control. In many cancers, TIL-Bs have demonstrated strong predictive and prognostic significance in the context of both standard treatments and immune checkpoint blockade, offering the prospect of new therapeutic opportunities that leverage their unique immunological properties. Drawing insights from autoimmunity, we review the molecular phenotypes, architectural contexts, antigen specificities, effector mechanisms and regulatory pathways relevant to TIL-Bs in human cancer. Although the field is young, the emerging picture is that TIL-Bs promote antitumour immunity through their unique mode of antigen presentation to T cells; their role in assembling and perpetuating immunologically 'hot' tumour microenvironments involving T cells, myeloid cells and natural killer cells; and their potential to combat immune editing and tumour heterogeneity through the easing of self-tolerance mechanisms. We end by discussing the most promising approaches to enhance TIL-B responses in concert with other immune cell subsets to extend the reach, potency and durability of cancer immunotherapy.

CCL21 and beta-cell antigen releasing hydrogels as tolerance-inducing therapy in Type I diabetes

Type-I Diabetes (T1D) is caused by defective immunotolerance mechanisms enabling autoreactive T cells to escape regulation in lymphoid organs and destroy insulin-producing β-cells in the pancreas, leading to insulin dependence. Strategies to promote β-cell tolerance could arrest T1D. We previously showed that secretion of secondary lymphoid chemokine CCL21 by CCL21 transgenic β-cells induced tolerance and protected non-obese diabetic (NOD) mice from T1D. T1D protection was associated with formation of lymph node-like stromal networks containing tolerogenic fibroblastic reticular cells (FRCs). Here, we developed a polyethylene glycol (PEG) hydrogel platform with hydrolytically degradable PEG-diester dithiol crosslinkers to provide controlled and sustained delivery of CCL21 and β-cell antigens for at least 28 days in vitro and recapitulate properties associated with the tolerogenic environment of CCL21 transgenic β-cells in our previous studies. CCL21 and MHC-II restricted antigens were tethered to gels via simple click-chemistry while MHC-I restricted antigens were loaded in PEG-based polymeric nanovesicles and incorporated in the gel networks. CCL21 and antigen release kinetics depended on the PEG gel tethering strategy and the linkers. Importantly, in vitro functionality, chemotaxis, and activation of antigen-specific T cells were preserved. Implantation of CCL21 and β-cell antigen gels under the kidney capsule of pre-diabetic NOD mice led to enrichment of adoptively transferred antigen-specific T cells, formation of gp38 + FRC-like stromal cell networks, and increased regulation of specific T cells with reduced accumulation within pancreatic islets. Thus, our platform for sustained release of β-cell antigens and CCL21 immunomodulatory molecule could enable the development of antigen-specific tolerance therapies for T1D.

Role of tertiary lymphoid organs in the regulation of immune responses in the periphery

Tertiary lymphoid organs (TLOs) are collections of immune cells resembling secondary lymphoid organs (SLOs) that form in peripheral, non-lymphoid tissues in response to local chronic inflammation. While their formation mimics embryologic lymphoid organogenesis, TLOs form after birth at ectopic sites in response to local inflammation resulting in their ability to mount diverse immune responses. The structure of TLOs can vary from clusters of B and T lymphocytes to highly organized structures with B and T lymphocyte compartments, germinal centers, and lymphatic vessels (LVs) and high endothelial venules (HEVs), allowing them to generate robust immune responses at sites of tissue injury. Although our understanding of the formation and function of these structures has improved greatly over the last 30 years, their role as mediators of protective or pathologic immune responses in certain chronic inflammatory diseases remains enigmatic and may differ based on the local tissue microenvironment in which they form. In this review, we highlight the role of TLOs in the regulation of immune responses in chronic infection, chronic inflammatory and autoimmune diseases, cancer, and solid organ transplantation.

B Cells and Tertiary Lymphoid Structures: Friends or Foes in Cancer Immunotherapy?

Tumor cells pose a challenge to the adaptive immune system, and its key cell types, T and B cells, have frequently been associated with an improved prognosis. The success of immune checkpoint blockade has confirmed the relevance of T cells. However, the role of B cells is increasingly recognized, and highlighted in this review. Recent data suggest that tumors contain a diverse set of B cells reflecting different developmental states and exerting functions such as antigen presentation, antibody production, and regulatory effects. Further, B cells are frequently located in tertiary lymphoid structures (TLS), which are immune cell niches that sustain an immune response at sites of chronic inflammation. TLSs in tumors display substantial heterogeneity, ranging from cell aggregates to mature structures with an active germinal center. Recent studies have provided insights into initiation, cellular and spatial composition, and function of TLS in a variety of cancer types; however, several critical issues still need to be resolved. Currently, initial reports are discerning the role of TLSs in immunotherapy, with the majority of studies observing TLSs to confer favorable patient outcome. Finally, TLS induction in tumors is evaluated, with the therapeutic aim to reactivate the host immune response.

Microbial Colonization and Inflammation as Potential Contributors to the Lack of Therapeutic Success in Oral Squamous Cell Carcinoma

This review discusses the microenvironment of evolving and established conventional oral squamous cell carcinoma, by far the most common oral cancer. The focus of this paper is mainly on the more recent data that describe the role of microorganisms, host-microbial interactions, and in particular, the contributions of cell-surface toll-like receptors on immune system cells and on normal and malignant epithelial cells to their functions that support carcinogenesis. Because carcinomas arising at various host surfaces share much in common, additional information available from studies of other carcinomas is included in the discussion. Accumulating evidence reveals the complex toll-like receptor-mediated tumor-supporting input into many aspects of carcinogenesis via malignant cells, stromal immune cells and non-immune cells, complicating the search for effective treatments.

Immunomodulating Profile of Dental Mesenchymal Stromal Cells: A Comprehensive Overview

Dental mesenchymal stromal cells (MSCs) are multipotent cells present in dental tissues, characterized by plastic adherence in culture and specific surface markers (CD105, CD73, CD90, STRO-1, CD106, and CD146), common to all other MSC subtypes. Dental pulp, periodontal ligament, apical papilla, human exfoliated deciduous teeth, alveolar bone, dental follicle, tooth germ, and gingiva are all different sources for isolation and expansion of MSCs. Dental MSCs have regenerative and immunomodulatory properties; they are scarcely immunogenic but actively modulate T cell reactivity. in vitro studies and animal models of autoimmune diseases have provided evidence for the suppressive effects of dental MSCs on peripheral blood mononuclear cell proliferation, clearance of apoptotic cells, and promotion of a shift in the Treg/Th17 cell ratio. Appropriately stimulated MSCs produce anti-inflammatory mediators, such as transforming growth factor-β (TGF-β), prostaglandin E2, and interleukin (IL)-10. A particular mechanism through which MSCs exert their immunomodulatory action is via the production of extracellular vesicles containing such anti-inflammatory mediators. Recent studies demonstrated MSC-mediated inhibitory effects both on monocytes and activated macrophages, promoting their polarization to an anti-inflammatory M2-phenotype. A growing number of trials focusing on MSCs to treat autoimmune and inflammatory conditions are ongoing, but very few use dental tissue as a cellular source. Recent results suggest that dental MSCs are a promising therapeutic tool for immune-mediated disorders. However, the exact mechanisms responsible for dental MSC-mediated immunosuppression remain to be clarified, and impairment of dental MSCs immunosuppressive function in inflammatory conditions and aging must be assessed before considering autologous MSCs or their secreted vesicles for therapeutic purposes.

Tertiary lymphoid structures in cancer

Ectopic lymphoid aggregates, termed tertiary lymphoid structures (TLSs), are formed in numerous cancer types, and, with few exceptions, their presence is associated with superior prognosis and response to immunotherapy. In spite of their presumed importance, the triggers that lead to TLS formation in cancer tissue and the contribution of these structures to intratumoral immune responses remain incompletely understood. Here, we discuss the present knowledge on TLSs in cancer, focusing on (i) the drivers of TLS formation, (ii) the function and contribution of TLSs to the antitumor immune response, and (iii) the potential of TLSs as therapeutic targets in human cancers.

Ectopic germinal centers in the thymus accurately predict prognosis of myasthenia gravis after thymectomy

The ability of thymic histopathology to predict the long-term impact of thymectomy in non-thymomatous myasthenia gravis (NTMG) is mainly uncharted. We applied digital pathology to quantitatively characterize differences of thymic histology between early-onset (EOMG) and late-onset MG (LOMG) and to investigate the role of thymic changes for thymectomy outcomes in MG. We analyzed 83 thymic H&E slides from thymectomized NTMG patients, of which 69 had EOMG and 14 LOMG, using digital pathology open-access software QuPath. We compared the results to the retrospectively assessed clinical outcome at two years after thymectomy and at the last follow-up visit where complete stable remission and minimal use of medication were primary outcomes. The automated annotation pipeline was an effective and reliable way to analyze thymic H&E samples compared to manual annotation with mean intraclass correlation of 0.80. The ratio of thymic tissue to stroma and fat was increased in EOMG compared to LOMG (p = 8.7e-07), whereas no difference was observed in the ratio of medulla to cortex between these subtypes. AChRAb seropositivity correlated with the number of ectopic germinal centers (eGC; p = 0.00067) but not with other histological areas. Patients with an increased number of eGCs had better post-thymectomy outcomes at two years after thymectomy (p = 0.0035) and at the last follow-up (p = 0.0267). ROC analysis showed that eGC area predicts thymectomy outcome in EOMG with an AUC of 0.79. Digital pathology can thus help in providing a predictive tool to the clinician, the eGC number, to guide the post-thymectomy treatment decisions in EOMG patients.

Immune function and dysfunction are determined by lymphoid tissue efficacy

Lymphoid tissue returns to a steady state once each immune response is resolved, and although this occurs multiple times throughout life, its structural integrity and functionality remain unaffected. Stromal cells orchestrate cellular interactions within lymphoid tissue, and any changes to the microenvironment can have detrimental outcomes and drive disease. A breakdown in lymphoid tissue homeostasis can lead to a loss of tissue structure and function that can cause aberrant immune responses. This Review highlights recent advances in our understanding of lymphoid tissue function and remodelling in adaptive immunity and in disease states. We discuss the functional role of lymphoid tissue in disease progression and explore the changes to lymphoid tissue structure and function driven by infection, chronic inflammatory conditions and cancer. Understanding the role of lymphoid tissues in immune responses to a wide range of pathologies allows us to take a fuller systemic view of disease progression.

Lymphocyte-activating gene-3 expression is associated with tumor-infiltrating lymphocyte levels in HER2-positive breast cancers

Lymphocyte-activating gene-3 (LAG-3, CD223) is the third inhibitory receptor targeted for immunotherapy. Several clinical trials investigating the use of interventions targeting LAG-3 are underway. The exact signaling mechanism downstream of LAG-3 is largely unknown, especially in breast cancer. The prognostic significance of tumor-infiltrating lymphocytes (TILs) in breast cancer has been previously determined.Among 167 human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients, 90 and 78 patients were positive and negative for the hormone receptor, respectively. LAG-3 mRNA and protein expression levels in TILs were evaluated by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively, among 12 and 167 HER2-positive breast cancer samples, respectively.High expression of LAG-3 in TILs was significantly correlated with high levels of TILs (P = .003) and an abundance of tertiary lymphoid structures around invasive components (P = .014). In addition, high expression of LAG3 was significantly associated with positivity for programmed death-ligand 1 (PD-L1) in tumor cells, a high immunostaining score of PD-L1 in TILs, and a high total immunostaining score for PD-L1 in tumor cells and TILs (all, P < .001). High expression levels of LAG-3 mRNA were associated with high levels of TILs (P = .091).LAG-3 protein expression was not a prognostic factor in HER2-positive breast cancers, and LAG-3 expression in TILs was significantly associated with the levels of TILs in HER2-positive breast cancer, although it was not a prognostic factor.

Tertiary lymphoid structures in oral lichen planus and oral epithelial dysplasia with lichenoid features: A comparative study

OBJECTIVE

Tertiary lymphoid structures (TLSs) provide sites for antigen presentation and activation of lymphocytes, promoting their infiltration; thus, enhancing specific immune responses. The aim of this comparative cross-sectional study was to reveal the characteristics and influence of TLSs in oral lichen planus (OLP) and oral epithelial dysplasia (OED) with lichenoid features.

METHODS

Clinical information and samples of 51 OLP and 19 OED with lichenoid features were collected. Immunohistochemistry was performed, and the structures where CD20+ B cells and CD3+ T cells aggregated with peripheral lymph node addressin positive (PNAd+) vessels were defined as TLSs. The results and clinical information were analysed.

RESULT

TLS were found in 44 (86.3%) patients with OLP and 19 (100%) patients with OED. The TLS score was higher in OED group (p = 0.023), accompanied by an increased number of PNAd+ vessels. The TLS was significantly correlated with PNAd+ vessels (p = 0.027), CD20+ B (p < 0.001) and CD208+ dendritic cells (p = 0.001). Foxp3+ Treg cells but not CD8+ T cells infiltrated more severely in OED (p = 0.003) and increased when TLS score was high (p = 0.002).

CONCLUSIONS

This study revealed the widespread development of TLSs in the OLP and OED. The presence of TLSs showed a close relationship with dysplasia and may increase malignant potency by over-inducing Treg cells.

CXCL13 Neutralization Attenuates Neuropsychiatric Manifestations in Lupus-Prone Mice

Neuropsychiatric lupus (NPSLE), the nervous system presentation of systemic lupus erythematosus (SLE), remains challenging to treat due to its unclear pathogenesis and lack of available targeted therapies. A potential contributor to disease progression is brain tertiary lymphoid structures (TLS); these ectopic lymphoid follicles that can develop tissue-targeted antibodies have recently been described in the MRL/lpr lupus mouse strain, a classic model for studying NPSLE. The brains of MRL/lpr mice show a significant increase of CXCL13, an important chemokine in lymphoid follicle formation and retention that may also play a role in the disease progression of NPSLE. The aim of the present study was to inhibit CXCL13 and examine the effect of this intervention on lymphoid formation and the development of neurobehavioral manifestations in lupus mice. Female MRL/lpr mice were injected with an anti-CXCL13 antibody, an IgG1 isotype-matched antibody, or PBS either three times a week for 12 weeks intraperitoneally (IP) starting at 6-8 weeks of age, or continuously intracerebroventricularly (ICV) with an osmotic pump over a two-week period starting at 15 weeks of age. Cognitive dysfunction and depression-like behavior were assessed at the end of treatment. When treatment was delivered IP, anti-CXCL13 treated mice showed significant improvement in cognitive function when compared to control treated mice. Depression-like behavior was attenuated as well. Furthermore, mice that received anti-CXCL13 by the ICV route showed similar beneficial effects. However, the extent of lymphocyte infiltration into the brain and the general composition of the aggregates were not substantively changed by anti-CXCL13 irrespective of the mode of administration. Nevertheless, analysis of brain gene expression in anti-CXCL13 treated mice showed significant differences in key immunological and neuro-inflammatory pathways that most likely explained the improvement in the behavioral phenotype. Our results indicate that CXCL13 affects the behavioral manifestations in the MRL/lpr strain and is important to the pathogenesis of murine NPSLE, suggesting it as a potential therapeutic target.

Functional Th1-oriented T follicular helper cells that infiltrate human breast cancer promote effective adaptive immunity

We previously demonstrated that tumor-infiltrating lymphocytes (TIL) in human breast cancer sometimes form organized tertiary lymphoid structures (TLS) characterized by CXCL13-producing T follicular helper (Tfh) cells. The present study found that CD4+ Tfh TIL, CD8+ TIL, and TIL-B, colocalizing in TLS, all express the CXCL13 receptor CXCR5. An ex vivo functional assay determined that only activated, functional Th1-oriented Tfh TIL (PD-1hiICOSint phenotype) provide help for immunoglobulin and IFN-γ production. A functional Tfh TIL presence signals an active TLS, characterized by humoral (immunoglobulins, Ki-67+ TIL-B in active germinal centers) and cytotoxic (GZMB+CD8+ and GZMB+CD68+ TIL plus Th1 gene expression) immune responses. Analysis of active versus inactive TLS in untreated patients revealed that the former are associated with positive clinical outcomes. TLS also contain functional T follicular regulatory (Tfr) TIL, which are characterized by a CD25+CXCR5+GARP+FOXP3+ phenotype and a demethylated FOXP3 gene. Functional Tfr inhibited functional Tfh activities via a glycoprotein A repetitions predominant (GARP)-associated TGF-β-dependent mechanism. The activity of tumor-associated TLS was dictated by the relative balance between functional Tfh TIL and functional Tfr TIL. These data provide mechanistic insight into TLS processes orchestrated by functional Th1-oriented Tfh TIL, including TIL-B and CD8+ TIL activation and immunological memory generation. Tfh TIL, regulated by functional Tfr TIL, are an expected key target of PD-1/PD-L1 blockade.

Putative Immunological Functions of Inducible Skin-Associated Lymphoid Tissue in the Context of Mucosa-Associated Lymphoid Tissue

Acquired immunity is orchestrated in various lymphoid organs, including bone marrow, thymus, spleen, and lymph nodes in humans. However, mucosa-associated lymphoid tissue (MALT) is evolutionally known to be emerged in the oldest vertebrates as an immunological tissue for acquired immunity, much earlier than the advent of lymph nodes which appeared in endotherms. Furthermore, the lymphocytes which developed in MALT are known to circulate within the limited anatomical areas. Thus, MALT is comprehended as not the structure but the immune network dedicated to local immunity. As for the skin, skin-associated lymphoid tissue (SALT) was previously postulated; however, its existence has not been proven. Our group recently showed that aggregations of dendritic cells, M2 macrophages, and high endothelial venules (HEVs) are essential components to activate effector T cells in the murine contact hypersensitivity model and termed it as inducible SALT (iSALT) since it was a transient entity that serves for acquired immunity of the skin. Furthermore, in various human skin diseases, we reported that the ectopic formation of lymphoid follicles that immunohistochemically analogous to MALT and regarded them as human counterparts of iSALT. These data raised the possibility that SALT can exist as an inducible form, namely iSALT, which shares the biological significance of MALT. In this article, we revisit the evolution of immunological organs and the related components among vertebrates to discuss the conserved functions of MALT. Furthermore, we also discuss the putative characteristics and functions of iSALT in the context of the MALT concept.

Insights Into Unveiling a Potential Role of Tertiary Lymphoid Structures in Metastasis

Tertiary lymphoid structures (TLSs) develop in non-lymphatic tissue in chronic inflammation and cancer. TLS can mature to lymph node (LN) like structures with germinal centers and associated vasculature. TLS neogenesis in cancer is highly varied and tissue dependent. The role of TLS in adaptive antitumor immunity is of great interest. However, data also show that TLS can play a role in cancer metastasis. The importance of lymphatics in cancer distant metastasis is clear yet the precise detail of how various immunosurveillance mechanisms interplay within TLS and/or draining LN is still under investigation. As part of the tumor lymphatics, TLS vasculature can provide alternative routes for the establishment of the pre-metastatic niche and cancer dissemination. The nature of the cytokine and chemokine signature at the heart of TLS induction can be key in determining the success of antitumor immunity or in promoting cancer invasiveness. Understanding the biochemical and biomechanical factors underlying TLS formation and the resulting impact on the primary tumor will be key in deciphering cancer metastasis and in the development of the next generation of cancer immunotherapeutics.

The Impact of Programmed Cell Death on the Formation of Tertiary Lymphoid Structures

Tertiary lymphoid structures are clusters of lymphoid tissue that develop post-natally at sites of chronic inflammation. They have been described in association with infection, autoimmune disorders, cancer, and allograft rejection. In their mature stage, TLS function as ectopic germinal centers, favoring the local production of autoantibodies and cytokines. TLS formation tends to parallel the severity of tissue injury and they are usually indicative of locally active immune responses. The presence of TLS in patients with solid tumors is usually associated with a better prognosis whereas their presence predicts increased maladaptive immunologic activity in patients with autoimmune disorders or allograft transplantation. Recent data highlight a correlation between active cell death and TLS formation and maturation. Our group recently identified apoptotic exosome-like vesicles, released by apoptotic cells, as novel inducers of TLS formation. Here, we review mechanisms of TLS formation and maturation with a specific focus on the emerging importance of tissue injury, programmed cell death and extracellular vesicles in TLS biogenesis.

Alternative pathways for the development of lymphoid structures in humans

Lymphoid tissue inducer (LTi) cells are critical for inducing the differentiation of most secondary lymphoid organs (SLOs) in mice. In humans, JAK3 and γc deficiencies result in severe combined immunodeficiency (SCIDs) characterized by an absence of T cells, natural killer cells, innate lymphoid cells (ILCs), and presumably LTi cells. Some of these patients have undergone allogeneic stem cell transplantation (HSCT) in the absence of myeloablation, which leads to donor T cell engraftment, while other leukocyte subsets are of host origin. By using MRI to look for SLOs in nine of these patients 16 to 44 y after HSCT, we discovered that SLOs were exclusively found in the three areas of the abdomen that drain the intestinal tract. A postmortem examination of a child with γc-SCID who had died 3.5 mo after HSCT showed corticomedullary differentiation in the thymus, T cell zones in the spleen, and the appendix, but in neither lymph nodes nor Peyer patches. Tertiary lymphoid organs were observed in the lung. No RAR-related orphan receptor-positive LTi cells could be detected in the existing lymphoid structures. These results suggest that while LTi cells are required for the genesis of most SLOs in humans, SLO in the appendix and in gut-draining areas, as well as tertiary lymphoid organs, can be generated likely by LTi cell-independent mechanisms.

Prognostic Value of Tumor-Infiltrating Lymphocytes and Tertiary Lymphoid Structures in Epstein-Barr Virus-Associated and -Negative Gastric Carcinoma

Background

Tumor-infiltrating lymphocytes (TILs) are considered a manifestation of the host immune response against cancer and tertiary lymphoid structures (TLS) may contribute to lymphocytes recruitment. Both of them have been reported as potential prognostic parameters in some human malignancies. However, the roles of TILs, TLS, and their correlation in Epstein-Barr Virus-associated gastric carcinoma (EBVaGC) and EBV-negative gastric carcinoma (EBVnGC) are largely unknown.

Methods

To observe the correlation among TILs, TLS, and clinicopathological characteristics and their prognostic significance in EBVaGC and EBVnGC, respectively. TILs and TLS were assessed by morphology and/or immunohistochemistry, and accompanied by clinicopathological analysis from 846 gastric cancer patients in multiple institutions.

Results

Forty-two (5.0%) cases of EBVaGC and 804 cases of EBVnGC were identified by in situ hybridization, respectively. For EBVnGC, higher TILs grade was correlated with TLS-present. EBVnGC patients with high TILs grade and TLS-present exhibited survival benefits. TILs (P = 0.001) and TLS (P = 0.003), especially TILs & TLS (P < 0.001) were independent prognostic factors in EBVnGC. A nomogram was constructed and validated for predicting the probability of overall survival and performed well with a good calibration. No significant prognostic value was detected in EBVaGC.

Conclusion

TILs and TLS, especially TILs & TLS were promising prognostic indicators for overall survival in EBVnGC. TILs and TLS were highly overlapping in their extent and prognostic abilities, and may be considered as a coindicator of prognosis of gastric cancer. The evaluations of TILs and TLS are simple and can be assessed routinely in pathological diagnosis.

Tumor-Associated Tertiary Lymphoid Structures: From Basic and Clinical Knowledge to Therapeutic Manipulation

The tumor microenvironment is a complex ecosystem almost unique to each patient. Most of available therapies target tumor cells according to their molecular characteristics, angiogenesis or immune cells involved in tumor immune-surveillance. Unfortunately, only a limited number of patients benefit in the long-term of these treatments that are often associated with relapses, in spite of the remarkable progress obtained with the advent of immune checkpoint inhibitors (ICP). The presence of “hot” tumors is a determining parameter for selecting therapies targeting the patient immunity, even though some of them still do not respond to treatment. In human studies, an in-depth analysis of the organization and interactions of tumor-infiltrating immune cells has revealed the presence of an ectopic lymphoid organization termed tertiary lymphoid structures (TLS) in a large number of tumors. Their marked similarity to secondary lymphoid organs has suggested that TLS are an “anti-tumor school” and an “antibody factory” to fight malignant cells. They are effectively associated with long-term survival in most solid tumors, and their presence has been recently shown to predict response to ICP inhibitors. This review discusses the relationship between TLS and the molecular characteristics of tumors and the presence of oncogenic viruses, as well as their role when targeted therapies are used. Also, we present some aspects of TLS biology in non-tumor inflammatory diseases and discuss the putative common characteristics that they share with tumor-associated TLS. A detailed overview of the different pre-clinical models available to investigate TLS function and neogenesis is also presented. Finally, new approaches aimed at a better understanding of the role and function of TLS such as the use of spheroids and organoids and of artificial intelligence algorithms, are also discussed. In conclusion, increasing our knowledge on TLS will undoubtedly improve prognostic prediction and treatment selection in cancer patients with key consequences for the next generation immunotherapy.

Stromal cells in tertiary lymphoid structures: Architects of autoimmunity

The molecular mediators present within the inflammatory microenvironment are able, in certain conditions, to favor the initiation of tertiary lymphoid structure (TLS) development. TLS is organized lymphocyte clusters able to support antigen-specific immune response in non-immune organs. Importantly, chronic inflammation does not always result in TLS formation; instead, TLS has been observed to develop specifically in permissive organs, suggesting the presence of tissue-specific cues that are able to imprint the immune responses and form TLS hubs. Fibroblasts are tissue-resident cells that define the anatomy and function of a specific tissue. Fibroblast plasticity and specialization in inflammatory conditions have recently been unraveled in both immune and non-immune organs revealing a critical role for these structural cells in human physiology. Here, we describe the role of fibroblasts in the context of TLS formation and its functional maintenance in the tissue, highlighting their potential role as therapeutic disease targets in TLS-associated diseases.

Anti-CD20 Depletes Meningeal B Cells but Does Not Halt the Formation of Meningeal Ectopic Lymphoid Tissue

OBJECTIVE

To investigate whether anti-CD20 B-cell-depleting monoclonal antibodies (ɑCD20 mAbs) inhibit the formation or retention of meningeal ectopic lymphoid tissue (mELT) in a murine model of multiple sclerosis (MS).

METHODS

We used a spontaneous chronic experimental autoimmune encephalomyelitis (EAE) model of mice with mutant T-cell and B-cell receptors specific for myelin oligodendrocyte glycoprotein (MOG), which develop meningeal inflammatory infiltrates resembling those described in MS. ɑCD20 mAbs were administered in either a preventive or a treatment regimen. The extent and cellular composition of mELT was assessed by histology and immunohistochemistry.

RESULTS

ɑCD20 mAb, applied in a paradigm to either prevent or treat EAE, did not alter the disease course in either condition. However, ɑCD20 mAb depleted virtually all B cells from the meningeal compartment but failed to prevent the formation of mELT altogether. Because of the absence of B cells, mELT was less densely populated with immune cells and the cellular composition was changed, with increased neutrophil granulocytes.

CONCLUSIONS

These results demonstrate that, in CNS autoimmune disease, meningeal inflammatory infiltrates may form and persist in the absence of B cells. Together with the finding that ɑCD20 mAb does not ameliorate spontaneous chronic EAE with mELT, our data suggest that mELT may have yet unknown capacities that are independent of B cells and contribute to CNS autoimmunity.

In Sickness and in Health: The Immunological Roles of the Lymphatic System

The lymphatic system plays crucial roles in immunity far beyond those of simply providing conduits for leukocytes and antigens in lymph fluid. Endothelial cells within this vasculature are distinct and highly specialized to perform roles based upon their location. Afferent lymphatic capillaries have unique intercellular junctions for efficient uptake of fluid and macromolecules, while expressing chemotactic and adhesion molecules that permit selective trafficking of specific immune cell subsets. Moreover, in response to events within peripheral tissue such as inflammation or infection, soluble factors from lymphatic endothelial cells exert “remote control” to modulate leukocyte migration across high endothelial venules from the blood to lymph nodes draining the tissue. These immune hubs are highly organized and perfectly arrayed to survey antigens from peripheral tissue while optimizing encounters between antigen-presenting cells and cognate lymphocytes. Furthermore, subsets of lymphatic endothelial cells exhibit differences in gene expression relating to specific functions and locality within the lymph node, facilitating both innate and acquired immune responses through antigen presentation, lymph node remodeling and regulation of leukocyte entry and exit. This review details the immune cell subsets in afferent and efferent lymph, and explores the mechanisms by which endothelial cells of the lymphatic system regulate such trafficking, for immune surveillance and tolerance during steady-state conditions, and in response to infection, acute and chronic inflammation, and subsequent resolution.