CCL21 expression pattern of human secondary lymphoid organ stroma is conserved in inflammatory lesions with lymphoid neogenesis

Plasmin reduces human T cell arrest on endothelial-like cells by cleaving bound CCL21 from the cell surface

CCL21 is a key homeostatic chemokine best known for its role in lymphocyte homing and compartmentalization in the lymph node. CCL21 also plays a role in trans-endothelial migration and is known to be bound to the surface of endothelial cells in high endothelial venules and inflamed tissues. The effects of CCL21 are highly dependent on its form; full-length CCL21 can bind to the surface of endothelial cells and induce lymphocyte arrest and transendothelial migration, whereas truncated CCL21 cannot. Earlier literature indicates that plasmin can cleave CCL21 from the surface of immune cells, although the mechanism regulating this process on endothelial cells has not been studied. This study demonstrates that the human endothelial-like cell lines ECV304 (LS12) and HMEC-1 can bind the plasmin precursor plasminogen to their cell surface. Furthermore, ECV304 (LS12) cells could endogenously activate plasminogen, yielding plasmin that subsequently released cell surface CCL21. In contrast, cell-surface CCL21 was only released from HMEC-1 after exogenous tPA activated the surface-bound plasminogen. Finally, it was shown that plasmin reduced T cell adhesion to endothelial-like cells with cell surface CCL21 under shear stress conditions. Collectively, for the first time, these data demonstrate that plasmin can cleave endothelial cell surface CCL21, reducing T cell adhesion to endothelial cells under shear stress. Interestingly, this study also indicates that endothelial cells' differential expression of plasminogen activators may regulate plasmin availability and influence T-cell arrest.

C-C Chemokine 21-Expressing T-cell Zone Fibroblastic Reticular Cells, Abundant in Lymph Nodes, Are Absent in Cancer Lymphoid Stroma

Cancer tissue generally possesses an immunosuppressive microenvironment. However, some cancers are associated with lymphoid stroma (i.e., a widely developed tertiary lymphoid structure). The T-cell zone (paracortex) of secondary lymphoid organs, particularly lymph nodes, is characterized by an abundance of T-cell zone fibroblastic reticular cells (TCZ-FRCs) that express C-C motif chemokine ligand 21 (CCL21) and smooth muscle actin (SMA). We analyzed the presence of TCZ-FRCs in 30 cases of carcinomas with lymphoid stroma of the breast, stomach, colon, tongue, and skin. Immunohistochemistry corroborated the abundance of CCL21+ SMA+ TCZ-FRCs in the normal lymph nodes. In sharp contrast, all 30 carcinomas with lymphoid stroma displayed no CCL21+ SMA+ TCZ-FRCs despite the affluence of T cells. Real-time reverse transcription polymerase chain reaction confirmed a marked decrease in the messenger ribonucleic acid expression of CCL21 and its receptor C-C motif chemokine receptor 7 in cancer lymphoid stroma compared to that in lymph nodes. Next, we analyzed the T cell phenotypes. The cancer lymphoid stroma demonstrated an abundance of CD3+ CD62L- memory-type T cells, in contrast to the presence of CD3+ CD62L+ naïve- and central memory T cells in the T cell zone of lymphoid tissues. Our data demonstrated the following: 1) Cancer lymphoid stroma lacked TCZ-FRCs with abundance of more activated T cells than in lymph nodes and 2) these were common phenomena in cancer lymphoid stroma irrespective of the histological types and organs involved.

Distinct fibroblast functions associated with fibrotic and immune-mediated inflammatory diseases and their implications for therapeutic development

Fibroblasts are ubiquitous cells that can adopt many functional states. As tissue-resident sentinels, they respond to acute damage signals and shape the earliest events in fibrotic and immune-mediated inflammatory diseases. Upon sensing an insult, fibroblasts produce chemokines and growth factors to organize and support the response. Depending on the size and composition of the resulting infiltrate, these activated fibroblasts may also begin to contract or relax thus changing local stiffness within the tissue. These early events likely contribute to the divergent clinical manifestations of fibrotic and immune-mediated inflammatory diseases. Further, distinct changes to the cellular composition and signaling dialogue in these diseases drive progressive fibroblasts specialization. In fibrotic diseases, fibroblasts support the survival, activation and differentiation of myeloid cells, granulocytes and innate lymphocytes, and produce most of the pathogenic extracellular matrix proteins. Whereas, in immune-mediated inflammatory diseases, sequential accumulation of dendritic cells, T cells and B cells programs fibroblasts to support local, destructive adaptive immune responses. Fibroblast specialization has clear implications for the development of effective induction and maintenance therapies for patients with these clinically distinct diseases.

Tertiary lymphoid structures in autoimmune diseases

Tertiary lymphoid structures (TLSs) are organized lymphoid-like aggregations in non-lymphoid tissues. Tissues with chronic and persistent inflammation infiltration may drive and form ectopic germinal center-like structures, which are very common in autoimmune diseases, chronic infections, and tumor microenvironments. However, the mechanisms governing the formation of TLSs are still being explored. At present, it is not clear whether the formation of TLSs is associated with local uncontrolled immune inflammatory responses. While TLSs suggest a good prognosis in tumors, the opposite is true in autoimmune diseases. This review article will discuss the current views on initiating and maintaining TLSs and the potential therapeutic target in autoimmune diseases.

CCL21/CCR7 axis as a therapeutic target for autoimmune diseases

Chemokine receptor 7 (CCR7) is a G protein-coupled receptor containing 7 transmembrane domains that is expressed on various cells, such as naive T/B cells, central memory T cells, regulatory T cells, immature/mature dendritic cells (DCs), natural killer cells, and a minority of tumor cells. Chemokine ligand 21 (CCL21) is the known high-affinity ligand that binds to CCR7 and drives cell migration in tissues. CCL21 is mainly produced by stromal cells and lymphatic endothelial cells, and its expression is significantly increased under inflammatory conditions. Genome-wide association studies (GWAS) have shown a strong association between CCL21/CCR7 axis and disease severity in patients with rheumatoid arthritis, sjogren's syndrome, systemic lupus erythematosus, polymyositis, ankylosing spondylitis, and asthma. Disrupting CCL21/CCR7 interaction with antibodies or inhibitors prevents the migration of CCR7-expressing immune and non-immune cells at the site of inflammation and reduces disease severity. This review emphasizes the importance of the CCL21 /CCR7 axis in autoimmune diseases and evaluates its potential as a novel therapeutic target for these conditions.

Targets of total glucosides of paeony in the treatment of Sjogren syndrome: A network pharmacology study

BACKGROUND

We aimed to explore the underlying mechanism of the total glucoside of peony (TGP) in treating Sjogren syndrome (SS) using the network pharmacology approach.

METHODS

The protein targets of TGP and SS were identified by database search. Then, the intersection of the two groups was studied. The drug-target network between TGP and the overlapping genes was constructed, visualized, and analyzed by Cytoscape software. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment were performed to analyze these genes. Finally, the predictions of potential targets were evaluated by docking study.

RESULTS

Forty-six overlapping genes were discovered. The results suggested that TGP used in the treatment of SS is associated with cellular tumor antigen p53, neurotrophic tyrosine kinase receptor type 1, and epidermal growth factor receptor, as well as their related 3372 protein networks, which regulate intrinsic apoptotic signaling pathway, cellular response to oxidative stress, rhythmic process, and other processes. Molecular docking analysis proved that hydrogen bonding is the main form of interaction.

CONCLUSION

Our research provided the protein targets affected by TGP in SS treatment. The key targets (caspase 3, vascular endothelial growth factor A, glyceraldehyde-3-phosphate dehydrogenase, etc.), which involve 3372 proteins, are the multitarget mechanism of TGP in SS treatment.

The lymphatic vasculature in lung function and respiratory disease

The lymphatic vasculature maintains tissue homeostasis via fluid drainage in the form of lymph and immune surveillance due to migration of leukocytes through the lymphatics to the draining lymph nodes. Lymphatic endothelial cells (LECs) form the lymphatic vessels and lymph node sinuses and are key players in shaping immune responses and tolerance. In the healthy lung, the vast majority of lymphatic vessels are found along the bronchovascular structures, in the interlobular septa, and in the subpleural space. Previous studies in both mice and humans have shown that the lymphatics are necessary for lung function from the neonatal period through adulthood. Furthermore, changes in the lymphatic vasculature are observed in nearly all respiratory diseases in which they have been analyzed. Recent work has pointed to a causative role for lymphatic dysfunction in the initiation and progression of lung disease, indicating that these vessels may be active players in pathologic processes in the lung. However, the mechanisms by which defects in lung lymphatic function are pathogenic are understudied, leaving many unanswered questions. A more comprehensive understanding of the mechanistic role of morphological, functional, and molecular changes in the lung lymphatic endothelium in respiratory diseases is a promising area of research that is likely to lead to novel therapeutic targets. In this review, we will discuss our current knowledge of the structure and function of the lung lymphatics and the role of these vessels in lung homeostasis and respiratory disease.

Decoding the Mechanism of CheReCunJin Formula in Treating Sjögren's Syndrome Based on Network Pharmacology and Molecular Docking

Background

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by progressive oral and ocular dryness that correlates poorly with autoimmune damage to the glands. CheReCunJin (CRCJ) formula is a prescription formulated according to the Chinese medicine theory for SS treatment.

Objective

This study aimed to explore the underlying mechanisms of CRCJ against SS.

Methods

The databases, including Traditional Chinese Medicine System Pharmacology, Encyclopedia of Traditional Chinese Medicine, Bioinformatics Analysis Tool for the molecular mechanism of Traditional Chinese Medicine, and Traditional Chinese Medicine Integrated Databases, obtained the active ingredients and predicted targets of CRCJ. Then, DrugBank, Therapeutic Target Database, Genecards, Comparative Toxicogenomics Database, and DisGeNET disease databases were used to screen the predicted targets of SS. Intersected targets of CRCJ and SS were visualized by using Venn diagrams. The overlapping targets were uploaded to the protein-protein interaction network analysis search tool. Cytoscape 3.8.2 software constructed a "compound-targets-disease" network. Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes analyses characterized potential targets' biological functions and pathways. AutoDock Vina 1.1.2 software was used to research and verify chemical effective drug components and critical targets.

Results

From the database, we identified 878 active components and 2578 targets of CRCJ, and 827 SS-related targets. 246 SS-related genes in CRCJ were identified by intersection analysis, and then ten hub genes were identified as crucial potential targets from PPI, including ALB, IL-6, TNF, INS, AKT1, IL1B, VEGFA, TP53, JUN, and TLR4. The process of CRCJ action against SS was mainly involved in human cytomegalovirus infection and Th17 cell differentiation, as well as the toll-like receptor signaling and p53 signaling pathways. Molecular docking showed that the bioactive compounds of CRCJ had a good binding affinity with hub targets.

Conclusions

The results showed that CRCJ could activate multiple pathways and treat SS through multiple compounds and targets. This study lays a foundation for better elucidation of the molecular mechanism of CRCJ in the treatment of SS, and also provides basic guidance for future research on Chinese herbal compounds.

Dynamic spectrum of ectopic lymphoid B cell activation and hypermutation in the RA synovium characterized by NR4A nuclear receptor expression

Ectopic lymphoid structures (ELS) can develop in rheumatoid arthritis (RA) synovial tissue, but the precise pathways of B cell activation and selection are not well understood. Here, we identify a synovial B cell population characterized by co-expression of a family of orphan nuclear receptors (NR4A1-3), which is highly enriched in RA synovial tissue. A transcriptomic profile of NR4A synovial B cells significantly overlaps with germinal center light zone B cells and an accrual of somatic hypermutation that correlates with loss of naive B cell state. NR4A B cells co-express lymphotoxins α and β and IL-6, supporting functions in ELS promotion. Expanded and shared clones between synovial NR4A B cells and plasma cells and the rapid upregulation with BCR stimulation point to in situ differentiation. Together, we identify a dynamic progression of B cell activation in RA synovial ELS, with NR4A transcription factors having an important role in local adaptive immune responses.

Fibroblasts as immune regulators in infection, inflammation and cancer

In chronic infection, inflammation and cancer, the tissue microenvironment controls how local immune cells behave, with tissue-resident fibroblasts emerging as a key cell type in regulating activation or suppression of an immune response. Fibroblasts are heterogeneous cells, encompassing functionally distinct populations, the phenotypes of which differ according to their tissue of origin and type of inciting disease. Their immunological properties are also diverse, ranging from the maintenance of a potent inflammatory environment in chronic inflammation to promoting immunosuppression in malignancy, and encapsulating and incarcerating infectious agents within tissues. In this Review, we compare the mechanisms by which fibroblasts control local immune responses, as well as the factors regulating their inflammatory and suppressive profiles, in different tissues and pathological settings. This cross-disease perspective highlights the importance of tissue context in determining fibroblast-immune cell interactions, as well as potential therapeutic avenues to exploit this knowledge for the benefit of patients with chronic infection, inflammation and cancer.

Chronic Pancreatitis and the Development of Pancreatic Cancer

Pancreatitis is a fibro-inflammatory disorder of the pancreas that can occur acutely or chronically as a result of the activation of digestive enzymes that damage pancreatic cells, which promotes inflammation. Chronic pancreatitis with persistent fibro-inflammation of the pancreas progresses to pancreatic cancer, which is the fourth leading cause of cancer deaths across the globe. Pancreatic cancer involves cross-talk of inflammatory, proliferative, migratory, and fibrotic mechanisms. In this review, we discuss the role of cytokines in the inflammatory cell storm in pancreatitis and pancreatic cancer and their role in the activation of SDF1α/CXCR4, SOCS3, inflammasome, and NF-κB signaling. The aberrant immune reactions contribute to pathological damage of acinar and ductal cells, and the activation of pancreatic stellate cells to a myofibroblast-like phenotype. We summarize several aspects involved in the promotion of pancreatic cancer by inflammation and include a number of regulatory molecules that inhibit that process.

Contribution of Heparan Sulphate Binding in CCL21-Mediated Migration of Breast Cancer Cells

Simple Summary

Breast cancer is a leading cause of cancer-related deaths worldwide, predominantly caused by metastasis. Chemokine receptor CCR7 and its ligand CCL21 are implicated in the metastasis of breast cancer to the lymph nodes. Chemokine function is dependent upon binding to their specific chemokine receptors and negatively charged molecules on the cell surface (heparan sulphate). The role of heparan sulphate in CCR7-mediated lymph node metastasis was investigated by creating a non-heparan sulphate binding mutant chemokine CCL21. Mutant-CCL21 was tested in vitro in a range of assays, including cell migration, calcium flux and surface plasmon resonance spectroscopy. Mutant-CCL21 induced leukocyte chemotaxis in diffusion gradients but did not stimulate trans-endothelial migration of breast cancer cells. A murine model was used to assess the potential of mutant-CCL21 to prevent lymph node metastasis in vivo. Lymph node metastasis was significantly reduced by the administration of mutant-CCL21 compared to the control. Targeting chemokine–heparan sulphate interactions may be a promising approach to inhibit chemokine activity and metastasis.

Abstract

Chemokine receptor CCR7 is implicated in the metastasis of breast cancer to the lymph nodes. Chemokine function is dependent upon their binding to both cell-surface heparan sulphate (HS) and to their specific receptors; thus, the role of HS in CCR7-mediated lymph node metastasis was investigated by creating a non-HS binding chemokine CCL21 (mut-CCL21). Mut-CCL21 (Δ103–134) induced leukocyte chemotaxis in diffusion gradients but did not stimulate trans-endothelial migration of PBMCs (p < 0.001) and 4T1-Luc cells (p < 0.01). Furthermore, the effect of heparin and HS on the chemotactic properties of wild-type (WT) and mut-CCL21 was examined. Interestingly, heparin and HS completely inhibit the chemotaxis mediated by WT-CCL21 at 250 and 500 µg/mL, whereas minimal effect was seen with mut-CCL21. This difference could potentially be attributed to reduced HS binding, as surface plasmon resonance spectroscopy showed that mut-CCL21 did not significantly bind HS compared to WT-CCL21. A murine model was used to assess the potential of mut-CCL21 to prevent lymph node metastasis in vivo. Mice were injected with 4T1-Luc cells in the mammary fat pad and treated daily for a week with 20 µg mut-CCL21. Mice were imaged weekly with IVIS and sacrificed on day 18. Luciferase expression was significantly reduced in lymph nodes from mice that had been treated with mut-CCL21 compared to the control (p = 0.0148), suggesting the potential to target chemokine binding to HS as a therapeutic option.

CLEC-2 Prevents Accumulation and Retention of Inflammatory Macrophages During Murine Peritonitis

Platelets play a key role in the development, progression and resolution of the inflammatory response during sterile inflammation and infection, although the mechanism is not well understood. Here we show that platelet CLEC-2 reduces tissue inflammation by regulating inflammatory macrophage activation and trafficking from the inflamed tissues. The immune regulatory function of CLEC-2 depends on the expression of its ligand, podoplanin, upregulated on inflammatory macrophages and is independent of platelet activation and secretion. Mechanistically, platelet CLEC-2 and also recombinant CLEC-2-Fc accelerates actin rearrangement and macrophage migration by increasing the expression of podoplanin and CD44, and their interaction with the ERM proteins. During ongoing inflammation, induced by lipopolysaccharide, treatment with rCLEC-2-Fc induces the rapid emigration of peritoneal inflammatory macrophages to mesenteric lymph nodes, thus reducing the accumulation of inflammatory macrophages in the inflamed peritoneum. This is associated with a significant decrease in pro-inflammatory cytokine, TNF-α and an increase in levels of immunosuppressive, IL-10 in the peritoneum. Increased podoplanin expression and actin remodelling favour macrophage migration towards CCL21, a soluble ligand for podoplanin and chemoattractant secreted by lymph node lymphatic endothelial cells. Macrophage efflux to draining lymph nodes induces T cell priming. In conclusion, we show that platelet CLEC-2 reduces the inflammatory phenotype of macrophages and their accumulation, leading to diminished tissue inflammation. These immunomodulatory functions of CLEC-2 are a novel strategy to reduce tissue inflammation and could be therapeutically exploited through rCLEC-2-Fc, to limit the progression to chronic inflammation.

High endothelial venules (HEVs) in immunity, inflammation and cancer

High endothelial venules (HEVs) are specialized blood vessels mediating lymphocyte trafficking to lymph nodes (LNs) and other secondary lymphoid organs. By supporting high levels of lymphocyte extravasation from the blood, HEVs play an essential role in lymphocyte recirculation and immune surveillance for foreign invaders (bacterial and viral infections) and alterations in the body’s own cells (neoantigens in cancer). The HEV network expands during inflammation in immune-stimulated LNs and is profoundly remodeled in metastatic and tumor-draining LNs. HEV-like blood vessels expressing high levels of the HEV-specific sulfated MECA-79 antigens are induced in non-lymphoid tissues at sites of chronic inflammation in many human inflammatory and allergic diseases, including rheumatoid arthritis, Crohn’s disease, allergic rhinitis and asthma. Such vessels are believed to contribute to the amplification and maintenance of chronic inflammation. MECA-79⁺ tumor-associated HEVs (TA-HEVs) are frequently found in human tumors in CD3⁺ T cell-rich areas or CD20⁺ B-cell rich tertiary lymphoid structures (TLSs). TA-HEVs have been proposed to play important roles in lymphocyte entry into tumors, a process essential for successful antitumor immunity and lymphocyte-mediated cancer immunotherapy with immune checkpoint inhibitors, vaccines or adoptive T cell therapy. In this review, we highlight the phenotype and function of HEVs in homeostatic, inflamed and tumor-draining lymph nodes, and those of HEV-like blood vessels in chronic inflammatory diseases. Furthermore, we discuss the role and regulation of TA-HEVs in human cancer and mouse tumor models.

A Requirement of Protein Geranylgeranylation for Chemokine Receptor Signaling and Th17 Cell Function in an Animal Model of Multiple Sclerosis

Precisely controlled lymphocyte migration is critically required for immune surveillance and successful immune responses. Lymphocyte migration is strictly regulated by chemokines and chemokine receptors. Here we show that protein geranylgeranylation, a form of post-translational protein lipid modification, is required for chemokine receptor-proximal signaling. Mature thymocytes deficient for protein geranylgeranylation are impaired for thymus egress. Circulating mature T cells lacking protein geranylgeranylation fail to home to secondary lymphoid organs or to transmigrate in response to chemokines in vitro. Mechanistically, protein geranylgeranylation modifies the γ-subunits of the heterotrimeric small GTPases that are essential for chemokine receptor signaling. In addition, protein geranylgeranylation also promotes the differentiation of IL-17-producing T helper cells while inhibiting the differentiation of Foxp3+ regulatory T cells. Finally, mice with T cell lineage-specific deficiency of protein geranylgeranylation are resistant to experimental autoimmune encephalomyelitis induction. This study elucidated a critical role of protein geranylgeranylation in regulating T lymphocyte migration and function.

Induction of High Endothelial Venule-like Vessels in Oral and Cutaneous Lichen Planus: A Comparative Study

Lichen planus (LP) is a chronic inflammatory mucocutaneous disease involving the oral mucosa and skin. Both oral LP (OLP) and cutaneous LP (CLP) are histopathologically characterized by dense subepithelial lymphocyte infiltrates; however, the mechanisms underlying lymphocyte recruitment to sites of LP lesions are not fully understood. Here, we assessed the induction of peripheral lymph node addressin (PNAd)-expressing high endothelial venule (HEV)-like vessels in 19 OLP and 17 CLP cases. To do so, we performed immunohistochemical staining for PNAd and CD34, followed by quantitative analysis. We also conducted triple immunohistochemistry for PNAd and either CD3 and CD20 or CD4 and CD8 to identify the lymphocyte subset preferentially recruited via HEV-like vessels. PNAd-expressing HEV-like vessels were induced in and around lymphocyte aggregates in all cases of OLP and in 10 of 17 CLP cases, and these vessels were more frequently observed in OLP relative to CLP. Although the number of T-cells attached per HEV-like vessel exceeded the number of B-cells in both OLP and CLP, the number of CD4⁺ T-cells attached was greater than the number of CD8⁺ T-cells only in OLP. These findings combined suggest that PNAd-expressing HEV-like vessels play a more important role in the pathogenesis of OLP compared with CLP.

Ectopic Lymphoid Organs and Immune-Mediated Diseases: Molecular Basis for Pharmacological Approaches

Chronic inflammation is the result a persistent increase in the expression of several proinflammatory pathways with impaired inflammatory resolution. Ectopic lymphoid organs (ELOs), untypical lymphoid annexes, emerge during chronic inflammation and contribute to the physiopathology of chronic inflammatory disorders. This review discusses the pathophysiological role of ELOs in the progression of immune-mediated inflammatory diseases (IMIDs), including multiple sclerosis (MS), rheumatoid arthritis (RA), inflammatory bowel disease (IBD), atherosclerosis, and Sjögren syndrome (SSj). The molecular pathways underlying the emergence of ELOs are of interest for the development of novel pharmacological approaches for the management of chronic inflammatory diseases.

Chronic lung allograft dysfunction post-lung transplantation: The era of bronchiolitis obliterans syndrome and restrictive allograft syndrome

Chronic lung allograft dysfunction (CLAD) following lung transplantation limits long-term survival considerably. The main reason for this is a lack of knowledge regarding the pathological condition and the establishment of treatment. The consensus statement from the International Society for Heart and Lung Transplantation on CLAD in 2019 classified CLAD into two main phenotypes: Bronchiolitis obliterans syndrome and restrictive allograft syndrome. Along with this clear classification, further exploration of the mechanisms and the development of appropriate prevention and treatment strategies for each phenotype are desired. In this review, we summarize the new definition of CLAD and update and summarize the existing knowledge on the underlying mechanisms of bronchiolitis obliterans syndrome and restrictive allograft syndrome, which have been elucidated from clinicopathological observations and animal experiments worldwide.

Tertiary Lymphoid Organs in Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease. RA mainly affects the joints, with inflammation of the synovial membrane, characterized by hyperplasia, neo-angiogenesis, and immune cell infiltration that drives local inflammation and, if untreated, can lead to joint destruction and disability. In parallel to the well-known clinical heterogeneity, the underlying synovitis can also be significantly heterogeneous. In particular, in about 40% of patients with RA, synovitis is characterized by a dense lymphocytic infiltrate that can acquire the features of fully functional tertiary lymphoid organs (TLO). These structures amplify autoimmunity and inflammation locally associated with worse prognosis and potential implications for treatment response. Here, we will review the current knowledge on TLO in RA, with a focus on their pathogenetic and clinical relevance.

Chronic Inflammation: A Common Promoter in Tertiary Lymphoid Organ Neogenesis

Tertiary lymphoid organs (TLOs) frequently develop locally in adults in response to non-resolving inflammation. Chronic inflammation leads to the differentiation of stromal fibroblast cells toward lymphoid tissue organizer-like cells, which interact with lymphotoxin α1β2+ immune cells. The interaction initiates lymphoid neogenesis by recruiting immune cells to the site of inflammation and ultimately leads to the formation of TLOs. Mature TLOs harbor a segregated T-cell zone, B-cell follicles with an activated germinal center, follicular dendritic cells, and high endothelial venules, which architecturally resemble those in secondary lymphoid organs. Since CXCL13 and LTα₁β₂ play key roles in TLO neogenesis, they might constitute potential biomarkers of TLO activity. The well-developed TLOs actively regulate local immune responses and influence disease progression, and they are thereby regarded as the powerhouses of local immunity. In this review, we recapitulated the determinants for TLOs development, with great emphasis on the fundamental role of chronic inflammation and tissue-resident stromal cells for TLO neogenesis, hence offering guidance for therapeutic interventions in TLO-associated diseases.

Exploiting CD22 To Selectively Tolerize Autoantibody Producing B-Cells in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that primarily affects the synovial joints and can lead to bone erosion and cartilage damage. One hallmark of RA is anticitrullinated protein autoantibodies (ACPA) and memory citrulline-specific B-cells, which have been implicated in RA pathogenesis. While depletion of B-cells with Rituximab improves clinical responses in RA patients, this treatment strategy leaves patients susceptible to infections. Here we use of Siglec-engaging Tolerance-inducing Antigenic Liposomes (STALs) to selectively target the citrulline-specific B-cells. ACPA production from purified human RA patients' B-cells in vitro was achieved through a set of stimulation conditions, which includes the following: BAFF, anti-CD40, IL-21, and LPS. In vivo generation of citrulline specific B-cells and ACPA production was accomplished by antigenic liposomes consisting of monophosphoryl lipid A (MPLA) and a cyclic citrullinated peptide (CCP) administered to SJL/J mice. We show that STALs that codisplay a high affinity CD22 glycan ligand and synthetic citrullinated antigen (CCP STALs) can prevent ACPA production from RA patients' memory B-cells in vitro. These CCP STALs were also effective in inducing tolerance to citrullinated antigens in SJL/J mice. The results demonstrate that tolerization of the B-cells responsible for ACPA can be achieved by exploiting the inhibitory receptor CD22 with high-affinity glycan ligands. Such a treatment strategy could be beneficial in the treatment of RA.

Redox-Mediated Mechanisms Fuel Monocyte Responses to CXCL12/HMGB1 in Active Rheumatoid Arthritis

Chemokine synergy-inducing molecules are emerging as regulating factors in cell migration. The alarmin HMGB1, in its reduced form, can complex with CXCL12 enhancing its activity on monocytes via the chemokine receptor CXCR4, while the form containing a disulfide bond, by binding to TLR2 or TLR4, initiates a cascade of events leading to production of cytokines and chemokines. So far, the possibility that the CXCL12/HMGB1 heterocomplex could be maintained in chronic inflammation was debated, due to the release of reactive oxygen species. Therefore, we have assessed if the heterocomplex could remain active in Rheumatoid Arthritis (RA) and its relevance in the disease assessment. Monocytes from RA patients with active disease require a low concentration of HMGB1 to enhance CXCL12-induced migration, in comparison to monocytes from patients in clinical remission or healthy donors. The activity of the heterocomplex depends on disease activity, on the COX2 and JAK/STAT pathways, and is determined by the redox potential of the microenvironment. In RA, the presence of an active thioredoxin system correlates with the enhanced cell migration, and with the presence of the heterocomplex in the synovial fluid. The present study highlights how, in an unbalanced microenvironment, the activity of the thioredoxin system plays a crucial role in sustaining inflammation. Prostaglandin E2 stimulation of monocytes from healthy donors is sufficient to recapitulate the response observed in patients with active RA. The activation of mechanisms counteracting the oxidative stress in the extracellular compartment preserves HMGB1 in its reduced form, and contributes to fuel the influx of inflammatory cells. Targeting the heterocomplex formation and its activity could thus be an additional tool for dampening the inflammation sustained by cell recruitment, for those patients with chronic inflammatory conditions who poorly respond to current therapies.

Tertiary Lymphoid Structures: Autoimmunity Goes Local

Tertiary lymphoid structures (TLS) are frequently observed in target organs of autoimmune diseases. TLS present features of secondary lymphoid organs such as segregated T and B cell zones, presence of follicular dendritic cell networks, high endothelial venules and specialized lymphoid fibroblasts and display the mechanisms to support local adaptive immune responses toward locally displayed antigens. TLS detection in the tissue is often associated with poor prognosis of disease, auto-antibody production and malignancy development. This review focuses on the contribution of TLS toward the persistence of the inflammatory drive, the survival of autoreactive lymphocyte clones and post-translational modifications, responsible for the pathogenicity of locally formed autoantibodies, during autoimmune disease development.

Role of chemokines in ectopic lymphoid structures formation in autoimmunity and cancer

Ectopic (or tertiary) lymphoid structures (ELS) are organized aggregates of lymphocytes resembling secondary lymphoid organs and developing in chronically inflamed nonlymphoid tissues during persistent infections, graft rejection, autoimmune conditions, and cancer. In this review, we will first depict the mechanisms regulating ELS generation, focusing on the role played by lymphoid chemokines. We will then characterize ELS forming in target organs during autoimmune conditions, here exemplified by rheumatoid arthritis, and cancer, highlighting the relevance of the tissue-specific factors. Finally, we will discuss the clinical significance of ELS and the therapeutic potential of their inhibition and/or enhancement depending on the disease considered.

Shuttling Tolerogenic Dendritic Cells across the Blood-Brain Barrier In Vitro via the Introduction of De Novo C-C Chemokine Receptor 5 Expression Using Messenger RNA Electroporation

The use of tolerance-inducing dendritic cells (tolDCs) has been proven to be safe and well tolerated in the treatment of autoimmune diseases. Nevertheless, several challenges remain, including finding ways to facilitate the migration of cell therapeutic products to lymph nodes, and the site of inflammation. In the treatment of neuroinflammatory diseases, such as multiple sclerosis (MS), the blood-brain barrier (BBB) represents a major obstacle to the delivery of therapeutic agents to the inflamed central nervous system (CNS). As it was previously demonstrated that C-C chemokine receptor 5 (CCR5) may be involved in inflammatory migration of DCs, the aim of this study was to investigate CCR5-driven migration of tolDCs. Only a minority of in vitro generated vitamin D₃ (vitD₃)-treated tolDCs expressed the inflammatory chemokine receptor CCR5. Thus, messenger RNA (mRNA) encoding CCR5 was introduced by means of electroporation (EP). After mRNA EP, tolDCs transiently displayed increased levels of CCR5 protein expression. Accordingly, the capacity of mRNA electroporated tolDCs to transmigrate toward a chemokine gradient in an in vitro model of the BBB improved significantly. Neither the tolerogenic phenotype nor the T cell-stimulatory function of tolDCs was affected by mRNA EP. EP of tolDCs with mRNA encoding CCR5 enabled these cells to migrate to inflammatory sites. The approach used herein has important implications for the treatment of MS. Using this approach, tolDCs actively shuttle across the BBB, allowing in situ down-modulation of autoimmune responses in the CNS.

Molecular and Cellular Requirements for the Assembly of Tertiary Lymphoid Structures

At sites of chronic inflammation, recruited immune cells form structures that resemble secondary lymphoid organs (SLOs). Those are characterized by segregated areas of prevalent T- or B-cell aggregation, differentiation of high endothelial venules (HEVs) and local activation of resident stromal cells. B-cell proliferation and affinity maturation towards locally displayed autoantigens have been demonstrated at those sites, known as tertiary lymphoid structures (TLSs). TLS formation has been associated with local disease persistence and progression as well as increased systemic manifestations. While bearing a similar histological structure to SLO, the signals that regulate TLS and SLO formation can diverge, and a series of pro-inflammatory cytokines has been ascribed as responsible for TLS formation at different anatomical sites. Here we review the structural elements as well as the signals responsible for TLS aggregation, aiming to provide an overview to this complex immunological phenomenon.

Cellular and Vascular Components of Tertiary Lymphoid Structures

Inflammatory immune cells recruited at the site of chronic inflammation form structures that resemble secondary lymphoid organs (SLO). These are characterized by segregated areas of prevalent T- or B-cell aggregation, differentiation of high endothelial venules, and local activation of resident stromal cells, including lymphatic endothelial cells. B-cell proliferation and affinity maturation toward locally displayed autoantigens have been demonstrated at these sites, known as tertiary lymphoid structures (TLS). TLS formation during chronic inflammation has been associated with local disease persistence and progression, as well as increased systemic manifestations. While bearing a similar histological structure to SLO, the signals that regulate TLS and SLO formation can diverge and a series of pro-inflammatory cytokines have been ascribed as responsible for TLS formation at different anatomical sites. Moreover, for a long time the structural compartment that regulates TLS homeostasis, including survival and recirculation of leucocytes has been neglected. In this chapter, we summarize the novel data available on TLS formation, structural organization, and the functional and anatomical links connecting TLS and SLOs.

Spoiling for a Fight: B Lymphocytes As Initiator and Effector Populations within Tertiary Lymphoid Organs in Autoimmunity and Transplantation

Tertiary lymphoid organs (TLOs) develop at ectopic sites within chronically inflamed tissues, such as in autoimmunity and rejecting organ allografts. TLOs differ structurally from canonical secondary lymphoid organs (SLOs), in that they lack a mantle zone and are not encapsulated, suggesting that they may provide unique immune function. A notable feature of TLOs is the frequent presence of structures typical of germinal centers (GCs). However, little is known about the role of such GCs, and in particular, it is not clear if the B cell response within is autonomous, or whether it synergizes with concurrent responses in SLOs. This review will discuss ectopic lymphoneogenesis and the role of the B cell in TLO formation and subsequent effector output in the context of autoimmunity and transplantation, with particular focus on the contribution of ectopic GCs to affinity maturation in humoral immune responses and to the potential breakdown of self-tolerance and development of humoral autoimmunity.

Lymphatic Changes in Respiratory Diseases: More than Just Remodeling of the Lung?

Advances in our ability to identify lymphatic endothelial cells and differentiate them from blood endothelial cells have led to important progress in the study of lymphatic biology. Over the past decade, preclinical and clinical studies have shown that there are changes to the lymphatic vasculature in nearly all lung diseases. Efforts to understand the contribution of lymphatics and their growth factors to disease initiation, progression, and resolution have led to seminal findings establishing critical roles for lymphatics in lung biology spanning from the first breath after birth to asthma, tuberculosis, and lung transplantation. However, in other diseases, it remains unclear if lymphatics are part of the overall lung remodeling process or real contributors to disease pathogenesis. The goal of this Translational Review is to highlight some of the advances in our understanding of the role(s) of lymphatics in lung disease and shed light on the critical needs and unanswered questions that might lead to novel translational applications.

Ectopic lymphoid neogenesis in rheumatic autoimmune diseases

Ectopic lymphoid neogenesis often occurs in the target tissues of patients with chronic rheumatic autoimmune diseases such as rheumatoid arthritis, Sjögren syndrome and other connective tissue disorders, including systemic lupus erythematosus and myositis. However, the mechanisms of ectopic lymphoid-like structure (ELS) formation and function are not entirely understood. For example, it is unclear whether ELSs indicate distinct disease phenotypes or whether they are evolutionary manifestations of chronic inflammation. Also unclear is why ELSs form in some patients but not in others. Nonetheless, ELSs frequently display functional features of ectopic germinal centres and can actively contribute to the maintenance of autoimmunity through the production of disease-specific autoantibodies; furthermore, they seem to influence disease severity and response to both synthetic and biologic DMARDs. In this Review, we discuss current knowledge and gaps in understanding of ELS formation and function including their prevalence in the above rheumatic autoimmune diseases; the mechanisms underlying their formation, maintenance and function, including positive and negative regulatory pathways; their functional relevance in the perpetuation of autoimmunity; their relationship with disease phenotypes, clinical outcomes and response to treatment; and the potential for specific targeting of ELSs through novel therapeutic modalities.

Stromal Fibroblasts in Tertiary Lymphoid Structures: A Novel Target in Chronic Inflammation

Tertiary lymphoid structures (TLS) are organized aggregates of lymphocytes, myeloid, and stromal cells that provide ectopic hubs for acquired immune responses. TLS share phenotypical and functional features with secondary lymphoid organs (SLO); however, they require persistent inflammatory signals to arise and are often observed at target sites of autoimmune disease, chronic infection, cancer, and organ transplantation. Over the past 10 years, important progress has been made in our understanding of the role of stromal fibroblasts in SLO development, organization, and function. A complex and stereotyped series of events regulate fibroblast differentiation from embryonic life in SLOs to lymphoid organ architecture observed in adults. In contrast, TLS-associated fibroblasts differentiate from postnatal, locally activated mesenchyme, predominantly in settings of inflammation and persistent antigen presentation. Therefore, there are critical differences in the cellular and molecular requirements that regulate SLO versus TLS development that ultimately impact on stromal and hematopoietic cell function. These differences may contribute to the pathogenic nature of TLS in the context of chronic inflammation and malignant transformation and offer a window of opportunity for therapeutic interventions in TLS associated pathologies.

Gel-Trapped Lymphorganogenic Chemokines Trigger Artificial Tertiary Lymphoid Organs and Mount Adaptive Immune Responses In Vivo

We previously generated artificial lymph node-like tertiary lymphoid organs (artTLOs) in mice using lymphotoxin α-expressing stromal cells. Here, we show the construction of transplantable and functional artTLOs by applying soluble factors trapped in slow-releasing gels in the absence of lymphoid tissue organizer stromal cells. The resultant artTLOs were easily removable, transplantable, and were capable of attracting memory B and T cells. Importantly, artTLOs induced a powerful antigen-specific secondary immune response, which was particularly pronounced in immune-compromised hosts. Synthesis of functionally stable immune tissues/organs like those described here may be a first step to eventually develop immune system-based therapeutics. Although much needs to be learned from the precise mechanisms of action, they may offer ways in the future to reestablish immune functions to overcome hitherto untreatable diseases, including severe infection, cancer, autoimmune diseases, and various forms of immune deficiencies, including immune-senescence during aging.

Bimodal Expansion of the Lymphatic Vessels Is Regulated by the Sequential Expression of IL-7 and Lymphotoxin α1β2 in Newly Formed Tertiary Lymphoid Structures

Lymphangiogenesis associated with tertiary lymphoid structure (TLS) has been reported in numerous studies. However, the kinetics and dynamic changes occurring to the lymphatic vascular network during TLS development have not been studied. Using a viral-induced, resolving model of TLS formation in the salivary glands of adult mice we demonstrate that the expansion of the lymphatic vascular network is tightly regulated. Lymphatic vessel expansion occurs in two distinct phases. The first wave of expansion is dependent on IL-7. The second phase, responsible for leukocyte exit from the glands, is regulated by lymphotoxin (LT)βR signaling. These findings, while highlighting the tight regulation of the lymphatic response to inflammation, suggest that targeting the LTα₁β₂/LTβR pathway in TLS-associated pathologies might impair a natural proresolving mechanism for lymphocyte exit from the tissues and account for the failure of therapeutic strategies that target these molecules in diseases such as rheumatoid arthritis.

The chemotactic interaction between CCL21 and its receptor, CCR7, facilitates the progression of pancreatic cancer via induction of angiogenesis and lymphangiogenesis

BACKGROUND

In this study, we report the influence of CCL21 and its receptor, CCR7, on the progression of pancreatic cancer and illuminates the correlation between the CCL21/CCR7 axis and the angiogenesis and lymphangiogenesis of pancreatic adenocarcinoma (PAC).

METHODS

A total of 30 patients with pancreatic cancer was involved in the current study. The expression of CCL21 and CCR7 in cancerous tissues, paracancerous tissues and normal pancreas were investigated using real-time PCR, Western blot and immunohistochemistry, respectively. In addition, we assessed microvessel density (MVD) and microlymphatic vessel density (MLVD) in tumor tissues using immunohistochemistry.

RESULTS

Compared to paracancerous tissues and normal pancreas, CCL21 expression in cancerous tissues was detected at a significantly low level. In contrast, the CCR7 expression was considerably higher in cancerous tissues than in normal pancreas and paracancerous tissues. Additionally, a significant correlation between the expression pattern of the CCL21/CCR7 axis and clinicopathological features, such as lymph node metastasis, was identified. Furthermore, we found that CCL21 expression was significantly associated with MVD but not significantly associated with MLVD, while CCR7 expression was significantly associated with MLVD but not significantly associated with MVD.

CONCLUSIONS

The chemotactic interaction between CCR7 and its ligand, CCL21, may be a critical event during progression in pancreatic cancer, and its underlying mechanism may be induction of angiogenesis and lymphangiogenesis regulated by this chemotactic interaction.

Ectopic lymphoid follicles: inducible centres for generating antigen-specific immune responses within tissues

Lymphoid neogenesis is traditionally viewed as a pre‐programmed process that promotes the formation of lymphoid organs during development. Here, the spatial organization of T and B cells in lymph nodes and spleen into discrete structures regulates antigen‐specific responses and adaptive immunity following immune challenge. However, lymphoid neogenesis is also triggered by chronic or persistent inflammation. Here, ectopic (or tertiary) lymphoid organs frequently develop in inflamed tissues as a response to infection, auto‐immunity, transplantation, cancer or environmental irritants. Although these structures affect local immune responses, the contribution of these lymphoid aggregates to the underlining pathology are highly context dependent and can elicit either protective or deleterious outcomes. Here we review the cellular and molecular mechanisms responsible for ectopic lymphoid neogenesis and consider the relevance of these structures in human disease.

Differential ligand-signaling network of CCL19/CCL21-CCR7 system

Chemokine (C-C motif) receptor 7 (CCR7), a class A subtype G-Protein Coupled Receptor (GPCR), is involved in the migration, activation and survival of multiple cell types including dendritic cells, T cells, eosinophils, B cells, endothelial cells and different cancer cells. Together, CCR7 signaling system has been implicated in diverse biological processes such as lymph node homeostasis, T cell activation, immune tolerance, inflammatory response and cancer metastasis. CCL19 and CCL21, the two well-characterized CCR7 ligands, have been established to be differential in their signaling through CCR7 in multiple cell types. Although the differential ligand signaling through single receptor have been suggested for many receptors including GPCRs, there exists no resource or platform to analyse them globally. Here, first of its kind, we present the cell-type-specific differential signaling network of CCL19/CCL21-CCR7 system for effective visualization and differential analysis of chemokine/GPCR signaling.

Database URL:http:// www. netpath. org/ pathways? path_ id= NetPath_ 46.

Immunopathology of synovitis: from histology to molecular pathways

Increased knowledge about pathological processes active in inflammatory joint diseases is needed to initiate personalized medicine based on targeted treatments in the future. The molecular and cellular pathways that are active during joint inflammation may differ between the various inflammatory joint diseases, between different patient subgroups within one disease, or even between different stages of the disease in a single patient. In this review, we evaluate synovial inflammation in terms of descriptive histopathology through to more functional studies on human synovial tissue inflammation in RA and SpA, in phenotypic subgroups of RA and SpA patients, and during the disease course of both diseases.

Non-proliferating plasma cells detected in the salivary glands and bone marrow of autoimmune NOD.B10.H2b mice, a model for primary Sjögren's syndrome

Autoantibody secreting plasma cells (PCs) are essential contributors in the development of autoimmune conditions such as primary Sjögren's syndrome (pSS). Particularly, the long-lived PC subset residing in the bone marrow has shown to continuously produce autoantibodies, whilst remaining unaffected by immunosuppressive treatment. We have previously shown accumulation of potentially long-lived PCs in chronically inflamed salivary glands of pSS patients. In this study, we aimed to characterise the PC compartment in the salivary glands (the target organ for pSS) and bone marrow before the onset of the murine pSS like disease versus advanced diseases progression. Bromodeoxyuridine (BrdU) was incorporated to distinguish the long-lived PCs. Double immunohistochemical staining and immunofluorescence were then conducted on submandibular gland and bone marrow sections from 8- and 40-week-old mice to identify BrdU and CD138. BrdU(+) cells were detected in the submandibular glands of 8-week-old mice, and observed within all focal infiltrates by 40 weeks of age. Most CD138(+) PCs were however BrdU(-) and located predominantly on the periphery of these infiltrates. This observation was verified through immunofluorescence. A comparable staining pattern was observed in the bone marrow of 8- and 40-week-old NOD.B10.H2b mice, where some of the CD138(+) cells also expressed BrdU. Interestingly, megakaryocytes in the bone marrow of NOD.B10.H2b mice were detected in close proximity to CD138(+) cells, illustrating a possible presence of PC survival niches. Our results demonstrate the presence and accumulation of potentially long-lived PCs in NOD.B10.H2b mice as the disease advances.

Collagen induces maturation of human monocyte-derived dendritic cells by signaling through osteoclast-associated receptor

Osteoclast-associated receptor (OSCAR) is widely expressed on human myeloid cells. Collagen types (Col)I, II, and III have been described as OSCAR ligands, and ColII peptides can induce costimulatory signaling in receptor activator for NF-κB-dependent osteoclastogenesis. In this study, we isolated collagen as an OSCAR-interacting protein from the membranes of murine osteoblasts. We have investigated a functional outcome of the OSCAR-collagen interaction in human monocyte-derived dendritic cells (DCs). OSCAR engagement by ColI/II-induced activation/maturation of DCs is characterized by upregulation of cell surface markers and secretion of cytokines. These collagen-matured DCs (Col-DCs) were efficient drivers of allogeneic and autologous naive T cell proliferation. The T cells expanded by Col-DCs secreted cytokines with no clear T cell polarization pattern. Global RNA profiling revealed that multiple proinflammatory mediators, including cytokines and cytokine receptors, components of the stable immune synapse (namely CD40, CD86, CD80, and ICAM-1), as well as components of TNF and TLR signaling, are transcriptional targets of OSCAR in DCs. Our findings indicate the existence of a novel pathway by which extracellular matrix proteins locally drive maturation of DCs during inflammatory conditions, for example, within synovial tissue of rheumatoid arthritis patients, where collagens become exposed during tissue remodeling and are thus accessible for interaction with infiltrating precursors of DCs.

On naivety of T cells in inflammatory bowel disease: a review

: Little is known about different phases of T-cell maturation in gut mucosa. Based on current knowledge about the migratory pathways of naive and memory T cells, it is believed that access to peripheral, nonlymphoid tissues is restricted to memory T cells. Surprisingly, there is increasing evidence of high numbers of naive T cells in the chronically inflamed gut tissue of patients with inflammatory bowel disease. This could partially be explained by new formation of ectopic lymphoid organs. Ongoing recruitment of naive T cells at inflammatory sites might play a role in the immunopathogenesis of inflammatory bowel disease.

B cells in rheumatoid arthritis: from pathogenic players to disease biomarkers

The therapeutic benefit of depleting B cells in rheumatoid arthritis (RA) has refocused attention on B cells with increasing awareness on their role in autoimmunity and their function beyond autoantibody production. The rapid increase in our comprehension of B-cell pathobiology is progressively opening novel perspectives in the area of B cell-targeted therapies with the expectation to define more specific approaches able to preserve the homeostasis of the humoral response while disrupting the pathogenic components. In parallel, B-cell activity in RA is starting to be explored in its clinical value, in search of novel biomarkers embedded in the pathogenic process that could help classifying the disease and predicting its heterogeneous outcome beyond inflammation dynamics. In this review, we summarize current knowledge on the multiple roles that B cells play in several aspects of RA. We also analyze their distribution and potential function in different anatomic compartments with specific reference to the main sites in which the disease may be sustained and exert its detrimental effects: the systemic circulation, synovium, bone marrow, and draining lymph nodes. We also highlight novel data encouraging further research in the field of biomarkers related to B cells and their regulatory factors.

High expression levels of the B cell chemoattractant CXCL13 in rheumatoid synovium are a marker of severe disease

OBJECTIVE

The B cell chemoattractant chemokine ligand 13 (CXCL13) is emerging as a new biochemical marker in RA. This study was undertaken to dissect the relationship between CXCL13 expression levels in the synovium and clinico-pathological variables relevant to RA pathogenesis and outcome.

METHODS

Synovial tissues from 71 RA patients were evaluated by immunohistochemistry. Thirty paired samples were used for comparative gene expression analysis by quantitative real-time PCR. CXCL13 levels were analysed in relation to cellular, molecular and clinical features of inflammation, lymphocyte activation and joint damage.

RESULTS

In patients with early disease (<12 months duration), CXCL13 expression correlated significantly with synovial markers of local disease activity and systemic inflammation. Such correlation was less evident in established RA. Notably, the association with lymphocyte infiltration and with expression of B/T cell-related activation and proliferation genes, such as activation-induced cytidine deaminase, IFN-γ and IL-2, remained highly significant independent of disease duration and local disease activity. Patients featuring the highest levels of CXCL13 were more frequently ACPA positive and IgG ACPA titres were increased in the high CXCL13 expression group. Furthermore, the frequency of erosive disease on radiographs was significantly higher in the upper tertile of CXCL13 expression (P = 0.01 with adjustment for disease duration and ACPA). Accordingly, synovial CXCL13 and the local receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG) ratio significantly co-varied (ρ = 0.52, P < 0.01), independent of the level of local inflammation.

CONCLUSION

Synovial CXCL13 appears to be a marker of a more severe pattern of RA disease, characterized by increased lymphocyte activation and bone remodelling beyond the level of conventional markers of inflammation.

Lymphatic vessels and tertiary lymphoid organs

Tertiary lymphoid organs (TLOs) are accumulations of lymphoid cells in chronic inflammation that resemble LNs in their cellular content and organization, high endothelial venules, and lymphatic vessels (LVs). Although acute inflammation can result in defective LVs, TLO LVs appear to function normally in that they drain fluid and transport cells that respond to chemokines and sphingosine-1-phosphate (S1P) gradients. Molecular regulation of TLO LVs differs from lymphangiogenesis in ontogeny with a dependence on cytokines and hematopoietic cells. Ongoing work to elucidate the function and molecular regulation of LVs in TLOs is providing insight into therapies for conditions as diverse as lymphedema, autoimmunity, and cancer.

Plasma cells within granulomatous inflammation display signs pointing to autoreactivity and destruction in granulomatosis with polyangiitis

Introduction

Plasma cells residing in inflamed tissues produce antibodies in chronic inflammatory and systemic autoimmune diseases. This study examined if plasma cells, located within inflamed nasal tissue in granulomatosis with polyangiitis (GPA), express features potentially associated with the autoimmune and destructive character of this disease.

Methods

Ig gene mutation patterns of individual tissue-derived plasma cells from GPA (n = 5) were analyzed, by using laser-assisted microdissection followed by semi-nested polymerase chain reaction (PCR). Signs of B-lymphocyte maturation (ectopic lymphoid structures, ELS) and survival (a proliferation-inducing ligand, APRIL; B-cell maturation antigen, BCMA; transmembrane-activator and calcium modulator and cyclophilin interactor, TACI; receptor activator of nuclear factor κB ligand, RANKL) were examined in nasal tissues or serum, respectively, by using immunohistochemistry/fluorescence and enzyme-linked immunosorbent assay, ELISA.

Results

Plasma-cell derived Ig genes (light- and heavy-chain pairs, n = 4; heavy chains, n = 33) resembled mutation patterns seen in other autoimmune diseases, predominantly displaying selection against replacement mutations within the framework region of Ig genes (10 of 15), which is responsible for structural integrity. Ectopic lymphoid structures were similar between GPA and a disease control (that is, unspecific chronic rhinosinusitis. However, histomorphologic features distinguishing GPA from rhinosinusitis (that is, neutrophilic microabscess and granuloma) expressed considerable amounts of membrane-associated and secreted APRIL, respectively. The latter was co-localized with CD138 and found in close proximity to cells expressing IgG, TACI, and BCMA. Interestingly, plasma cells strongly expressed receptor activator of nuclear factor κB ligand (RANKL), apart from fibroblast-like cells.

Conclusions

Plasma cells within granulomatous inflammation appear to display features that might be required for autoreactivity and, possibly, RANKL-mediated destruction in GPA.

The role of viruses in autoreactive B cell activation within tertiary lymphoid structures in autoimmune diseases

TLS, characterized by the formation of ectopic B/T cell follicles with FDCs supporting an ectopic GC response, have been described in the target organs of several autoimmune diseases, including MS, RA, SS, and autoimmune thyroiditis. These structures represent functional niches, whereby autoreactive B cells undergo in situ affinity maturation and differentiation to autoantibody-producing cells, thus contributing to the progression and persistence of autoimmunity. Increasing evidence demonstrates that TLS can also develop in the context of cancer, as well as chronic infections. In this review, we collect recent evidences that highlights the relationship between persistent viral infection and the development of ectopic lymphoid structures in animal models and patients. Furthermore, we shall discuss the concept that whereas in physiological conditions, inducible TLS are critical for viral clearance and the establishment of protective immunity, but in the context of susceptible individuals, persistent viral infections may contribute, directly or indirectly, to the development of breach of tolerance against self-antigens and the development of autoimmunity through the formation of TLS.

New learnings on the pathophysiology of RA from synovial biopsies

PURPOSE OF REVIEW

To critically appraise the literature related to the pathophysiology of rheumatoid arthritis (RA) focusing on the contribution of synovial tissue pathology (synovitis) in determining diverse clinical outcome/therapeutic response.

RECENT FINDINGS

RA synovitis is highly heterogeneous with diverse cellular and molecular signatures (pathotypes) emerging as potential taxonomic classifiers of disease phenotypes.The challenge is to understand mechanistically the sophisticated interplay between systemic disease 'initiators' and joint-specific 'localizing/perpetuating' factors leading to disparate coupling of inflammation/tissue-destructive pathways and disease outcome. Synovial tissue analysis has been instrumental in enhancing understanding of R0A pathogenesis and developing targeted DMARD-biologic therapies. The next step is to elucidate the relationship of different synovial pathotypes/molecular signatures with therapeutic response/resistance in randomized clinical trials in order to develop effective therapies for 'resistant' patients. The development of ultrasound-guided synovial biopsy as a rapid, safe and well tolerated procedure that enables synovial tissue collection from most joints/patients will facilitate such studies.

SUMMARY

RA is a heterogeneous clinical and pathobiological entity. Specific pathways within synovial tissues are emerging as associated with diverse clinical evolution and therapeutic response/resistance that, if confirmed in randomized clinical trials, may lead to the development of synovial tissue analysis as a potential clinical tool for patient stratification.

Arthritis severity locus Cia4 is an early regulator of IL-6, IL-1β, and NF-κB activators' expression in pristane-induced arthritis

Cia4 is a locus on rat chromosome 7 that regulates disease severity and joint damage in models of rheumatoid arthritis, including pristane-induced arthritis (PIA). To identify molecular processes regulated by Cia4, synovial tissues from MHC-identical DA (severe erosive) and DA.F344(Cia4) congenics (mild nonerosive) rats were collected at preclinical and recent onset stages following the induction of PIA and analyzed for gene expression levels. Il6 levels were significantly higher in DA compared with congenics on day 10 (135-fold) after PIA induction (preclinical stage) and remained increased on days 14 (47.7-fold) and 18 (29.41-fold). Il6 increased before Il1b suggesting that Il6 could be driving Il1b expression and early synovial inflammation; 187 genes had significantly different expression levels and included inflammatory mediators increased in DA such Slpi (10.94-fold), Ccl7 (5.17-fold), and Litaf (2.09-fold). Syk or NF-κB activating and interacting genes, including Cd74 Ccl21, were increased in DA; 59 genes implicated in cancer-related phenotypes were increased in DA. Genes involved in cell metabolism, transport across membranes, and tissue protection such as Dgat1, Dhcr7, and Slc1a1 were increased in DA.F344(Cia4) congenics; 21 genes differentially expressed or expressed in only one of the strains were located within the Cia4 interval and could be the gene accounting for the arthritis effect. In conclusion, the Cia4 interval contains at least one new arthritis gene that regulates early Il6, Il1b expression, and other inflammatory mediators. This gene regulates the expression of cancer genes that could mediate the development of synovial hyperplasia and invasion, and cartilage and bone destruction.

Immunotargeting and eradication of orthotopic melanoma using a chemokine-enhanced DNA vaccine

DNA vaccines are attractive candidates for tumor immunotherapy. However, the potential of DNA vaccines in treating established malignant lesions has yet to be demonstrated. Here we demonstrate that transient alteration of either intratumoral or intradermal (ID) chemotactic gradients provide a favorable milieu for DNA vaccine-mediated activation of tumor-specific immune response in both prophylactic and therapeutic settings. Specifically, we show that priming of established B16 ID melanoma lesions via forced intratumoral expression of CCL21 boosted DNA vaccination-dependent systemic cytotoxic immune response leading to the regression of tumor nodules. In this setting, application of CCL20 was not effective likely due to the engagement of the regulatory T cells. However, priming of the skin at DNA vaccine administration sites outside the tumor bed with both CCL20 and CCL21 chemokines along with structural modifications of the DNA vaccine significantly improved vaccine efficacy. This optimized ID vaccination regimen led to the inhibition of distant established melanomas and prolonged tumor-free survival of mice observed in 60% of vaccinated animals with complete tumor remission in 30%. These effects were mediated by extranodal priming and activation of T cells at vaccine administration sites and progressive accumulation of systemic antigen-specific cytotoxic T cells (CTLs) on successive vaccinations. These results underscore the potential of chemokine-enhanced DNA vaccination to mount therapeutic immune response against established tumors.

Inflammatory lesions in the bone marrow of rheumatoid arthritis patients: a morphological perspective

The synovial tissue stands at the epicenter of joint pathology in rheumatoid arthritis (RA). As a primary target of the disease, studies on the synovium have provided invaluable insights into the mechanisms involved in disease pathogenesis. Recent work has, however, revealed the importance of a previously unseen anatomic compartment in direct contact with the joint space, namely the subchondral bone marrow. Bone marrow edema (BME) visible on magnetic resonance imaging (MRI) is clinically meaningful in both early and late RA as it associates with future development of bone erosions and poor functional outcomes. Although the histopathologic correlates of MRI-based BME in early RA remain obscure, studies in advanced disease are consistent in describing lymphocytic inflammatory infiltrates within the subchondral marrow cavity of affected joints. In this review, we discuss the nature of bone marrow lesions in patients with RA, analyze their relationship with synovitis, and explore their potential contribution to the pathological processes of the disease.