Lymphatic vessels and tertiary lymphoid organs

Interplay of immune and kidney resident cells in the formation of tertiary lymphoid structures in lupus nephritis

Kidney involvement confers significant morbidity and mortality in patients with systemic lupus erythematosus (SLE). The pathogenesis of lupus nephritis (LN) involves diverse mechanisms instigated by elements of the autoimmune response which alter the biology of kidney resident cells. Processes in the glomeruli and in the interstitium may proceed independently albeit crosstalk between the two is inevitable. Podocytes, mesangial cells, tubular epithelial cells, kidney resident macrophages and stromal cells with input from cytokines and autoantibodies present in the circulation alter the expression of enzymes, produce cytokines and chemokines which lead to their injury and damage of the kidney. Several of these molecules can be targeted independently to prevent and reverse kidney failure. Tertiary lymphoid structures with true germinal centers are present in the kidneys of patients with lupus nephritis and have been increasingly recognized to associate with poorer renal outcomes. Stromal cells, tubular epithelial cells, high endothelial vessel and lymphatic venule cells produce chemokines which enable the formation of structures composed of a T-cell-rich zone with mature dendritic cells next to a B-cell follicle with the characteristics of a germinal center surrounded by plasma cells. Following an overview on the interaction of the immune cells with kidney resident cells, we discuss the cellular and molecular events which lead to the formation of tertiary lymphoid structures in the interstitium of the kidneys of mice and patients with lupus nephritis. In parallel, molecules and processes that can be targeted therapeutically are presented.

Development and physiological functions of the lymphatic system: insights from human genetic studies of primary lymphedema

Primary lymphedema is a long-term (chronic) condition characterized by tissue lymph retention and swelling that can affect any part of the body, although it usually develops in the arms or legs. Due to the relevant contribution of the lymphatic system to human physiology, while this review mainly focuses on the clinical and physiological aspects related to the regulation of fluid homeostasis and edema, clinicians need to know that the impact of lymphatic dysfunction with a genetic origin can be wide ranging. Lymphatic dysfunction can affect immune function so leading to infection; it can influence cancer development and spread, and it can determine fat transport so impacting on nutrition and obesity. Genetic studies and the development of imaging techniques for the assessment of lymphatic function have enabled the recognition of primary lymphedema as a heterogenic condition in terms of genetic causes and disease mechanisms. In this review, the known biological functions of several genes crucial to the development and function of the lymphatic system are used as a basis for understanding normal lymphatic biology. The disease conditions originating from mutations in these genes are discussed together with a detailed clinical description of the phenotype and the up-to-date knowledge in terms of disease mechanisms acquired from in vitro and in vivo research models.

Tertiary Lymphoid Structures in the Central Nervous System: Implications for Glioblastoma

Glioblastoma is the most common and aggressive brain tumor, which is uniformly lethal due to its extreme invasiveness and the absence of curative therapies. Immune checkpoint inhibitors have not yet proven efficacious for glioblastoma patients, due in part to the low prevalence of tumor-reactive T cells within the tumor microenvironment. The priming of tumor antigen-directed T cells in the cervical lymph nodes is complicated by the shortage of dendritic cells and lack of appropriate lymphatic vessels within the brain parenchyma. However, recent data suggest that naive T cells may also be primed within brain tumor-associated tertiary lymphoid structures. Here, we review the current understanding of the formation of these structures within the central nervous system, and hypothesize that promotion of tertiary lymphoid structures could enhance priming of tumor antigen-targeted T cells and sensitize glioblastomas to cancer immunotherapy.

High Endothelial Venules: A Vascular Perspective on Tertiary Lymphoid Structures in Cancer

High endothelial venules (HEVs) are specialized postcapillary venules composed of cuboidal blood endothelial cells that express high levels of sulfated sialomucins to bind L-Selectin/CD62L on lymphocytes, thereby facilitating their transmigration from the blood into the lymph nodes (LN) and other secondary lymphoid organs (SLO). HEVs have also been identified in human and murine tumors in predominantly CD3⁺T cell-enriched areas with fewer CD20⁺B-cell aggregates that are reminiscent of tertiary lymphoid-like structures (TLS). While HEV/TLS areas in human tumors are predominantly associated with increased survival, tumoral HEVs (TU-HEV) in mice have shown to foster lymphocyte-enriched immune centers and boost an immune response combined with different immunotherapies. Here, we discuss the current insight into TU-HEV formation, function, and regulation in tumors and elaborate on the functional implication, opportunities, and challenges of TU-HEV formation for cancer immunotherapy.

Mesenteric lymphatic dysfunction promotes insulin resistance and represents a potential treatment target in obesity

Visceral adipose tissue (VAT) encases mesenteric lymphatic vessels and lymph nodes through which lymph is transported from the intestine and mesentery. Whether mesenteric lymphatics contribute to adipose tissue inflammation and metabolism and insulin resistance is unclear. Here we show that obesity is associated with profound and progressive dysfunction of the mesenteric lymphatic system in mice and humans. We find that lymph from mice and humans consuming a high-fat diet (HFD) stimulates lymphatic vessel growth, leading to the formation of highly branched mesenteric lymphatic vessels that 'leak' HFD-lymph into VAT and, thereby, promote insulin resistance. Mesenteric lymphatic dysfunction is regulated by cyclooxygenase (COX)-2 and vascular endothelial growth factor (VEGF)-C-VEGF receptor (R)3 signalling. Lymph-targeted inhibition of COX-2 using a glyceride prodrug approach reverses mesenteric lymphatic dysfunction, visceral obesity and inflammation and restores glycaemic control in mice. Targeting obesity-associated mesenteric lymphatic dysfunction thus represents a potential therapeutic option to treat metabolic disease.

Systemic Inflammation Response Index is an Independent Prognostic Indicator for Patients with Renal Cell Carcinoma Undergoing Laparoscopic Nephrectomy: A Multi-Institutional Cohort Study

Background

We conducted a multicenter clinical study to examine the prognostic value of the systemic inflammation response index (SIRI) in renal cell carcinoma (RCC) patients.

Methods

We collected patients who underwent nephrectomy from 2014 to 2019 at three centers (343 in the training group and 100 in the validation group). SIRI was created based on hemoglobin and lymphocyte to monocyte ratio (LMR). Kaplan–Meier curves and receiver operating characteristic (ROC) curves were used to analyze the effect of LMR, hemoglobin and SIRI on overall survival (OS) and cancer-specific survival (CSS) effects.

Results

In both the training and validation groups, SIRI was a better predictor of OS and CSS than LMR and hemoglobin. A total of 192 (56.0%) patients were included in grade 1, 108 (31.5%) in grade 2, and 43 (12.5%) in grade 3 based on SIRI in the training group. Higher SIRI was associated with worse prognosis. Multivariate cox regression analysis showed that SIRI was an independent prognostic risk factor for OS (grade 3 vs grade 1: HR=4.93; 95% CI 2.21–11.00, p < 0.001) and CSS (grade 3 vs grade 1: HR=6.29; 95% CI 2.28–17.39, p < 0.001) in patients with RCC. In addition, SIRI-based prognostic nomograms were able to better predict OS and CSS in RCC patients.

Conclusion

SIRI is an independent prognostic factor for patients undergoing laparoscopic nephrectomy for RCC, and a prognostic nomogram covering SIRI can better predict survival of RCC patients.

Non-contrast magnetic resonance lymphography (NCMRL) in cancer-related secondary lymphedema: acquisition technique and imaging findings

Cancer-related secondary lymphedema (LE) is a widespread issue, which markedly affects patients' quality of life. Its diagnosis is mainly clinical since there is no consensus on the best imaging technique that should be used to assess this pathology. Even if lymphedema treatment has been traditionally conservative and mainly based on compressive bandages and decongestive therapy, new surgical techniques are proving their effectiveness in the management of the disease and made proper assessment and characterization of lymphedema necessary. In this scenario, non-contrast magnetic resonance lymphography (NCMRL) is acquiring an increasing role, as a non-invasive imaging technique, useful for the analysis of LE. NCMRL is an effective tool in diagnosis confirmation, in providing information about the structural changes of the affected limbs, in grading this disorder, and provides a guide for LE management and treatment planning. This article aims to provide an overview of the literature regarding this examination, analyzing the acquisition technique, the interpretation of the imaging findings and their usefulness, the advantages and limits of this technique, to help the radiologist approach this relatively new investigation in cases of cancer-related LE.

Positron emission tomography and single photon emission computed tomography imaging of tertiary lymphoid structures during the development of lupus nephritis

Lymphoid neogenesis occurs in tissues targeted by chronic inflammatory processes, such as infection and autoimmunity. In systemic lupus erythematosus (SLE), such structures develop within the kidneys of lupus-prone mice ((NZBXNZW)F1) and are observed in kidney biopsies taken from SLE patients with lupus nephritis (LN). The purpose of this prospective longitudinal animal study was to detect early kidney changes and tertiary lymphoid structures (TLS) using in vivo imaging. Positron emission tomography (PET) by tail vein injection of 18-F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG)(PET/FDG) combined with computed tomography (CT) for anatomical localization and single photon emission computed tomography (SPECT) by intraperitoneal injection of ^99mTC labeled Albumin Nanocoll (^99mTC-Nanocoll) were performed on different disease stages of NZB/W mice (n = 40) and on aged matched control mice (BALB/c) (n = 20). By using one-way ANOVA analyses, we compared two different compartmental models for the quantitative measure of ¹⁸F-FDG uptake within the kidneys. Using a new five-compartment model, we observed that glomerular filtration of ^18FFDG in lupus-prone mice decreased significantly by disease progression measured by anti-dsDNA Ab production and before onset of proteinuria. We could not visualize TLS within the kidneys, but we were able to visualize pancreatic TLS using ^99mTC Nanocoll SPECT. Based on our findings, we conclude that the five-compartment model can be used to measure changes of FDG uptake within the kidney. However, new optimal PET/SPECT tracer administration sites together with more specific tracers in combination with magnetic resonance imaging (MRI) may make it possible to detect formation of TLS and LN before clinical manifestations.

Long-term B cell depletion associates with regeneration of kidney function

Background

Chronic kidney disease (CKD) is a common condition that increases mortality and the risk of cardiovascular and other morbidities regardless of underlying renal condition. Chronic inflammation promotes renal fibrosis. Recently, renal B cell infiltrates were described in chronic kidney disease of various etiologies beyond autoimmunity.

Methods

We here investigated B cells and indicators of tertiary lymphoid structure formation in human renal biopsies. Renal function was studied during long‐term B cell depletion in human patients with membranous nephropathy and with CKD of unknown origin.

Results

Cytokine profiles of tertiary lymphoid structure formation were detected in human renal interstitium in a range of kidney diseases. Complex B cell structures consistent with tertiary lymphoid organ formation were evident in human membranous nephropathy. Here, B cell density did not significantly associate with proteinuria severity, but with worse excretory renal function. Proteinuria responses mostly occurred within the first 6 months of B cell depletion. In contrast, recovery of excretory kidney function was observed only after 18 months of continuous therapy, consistent with a structural process. Renal tertiary lymphatic structures were also detected in the absence of autoimmune kidney disease. To start to address whether B cell depletion may affect CKD in a broader population, we assessed kidney function in neurologic patients with CKD of unknown origin. In this cohort, eGFR significantly increased within 24 months of B cell depletion.

Conclusion

Long‐term B cell depletion associated with significant improvement of excretory kidney function in human CKD. Kinetics and mechanisms of renal B cell aggregation should be investigated further to stratify the impact of B cells and their aggregates as therapeutic targets.

Implications of lymphatic alterations in the pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by intense immune dysregulation, gut microbiota imbalance, and intestinal epithelium destruction. Among the factors that contribute to the pathogenesis of IBD, lymphatics have received less attention, hence less studied, characterized, and explored. However, in recent years, the role of the lymphatic system in gastrointestinal pathophysiology continues to be highlighted. This paper examines the implications of lymphatic changes in IBD pathogenesis related to immune cells, gut microbiota, intestinal and mesenteric epithelial barrier integrity, and progression to colorectal cancer (CRC). Therapeutic targets of lymphatics in IBD studies are also presented. Available studies indicate that lymph nodes and other secondary lymphatic tissues, provide highly specialized microenvironments for mounting effective immune responses and that lymphatic integrity plays a significant role in small intestine homeostasis, where the lymphatic vasculature effectively controls tissue edema, leukocyte exit, bacterial antigen, and inflammatory chemokine clearance. In IBD, there are functional and morphological alterations in intestinal and mesenteric lymphatic vessels (more profoundly in Crohn's disease [CD] compared to ulcerative colitis [UC]), including lymphangiogenesis, lymphangiectasia, lymphadenopathy, and lymphatic vasculature blockade, affecting not only immunity but gut microbiota and epithelial barrier integrity. While increased lymphangiogenesis is primarily associated with a good prognosis of IBD, increased lymphangiectasia, lymphadenopathy, and lymphatic vessel occlusion correlate with poor prognosis. IBD therapies that target the lymphatic system seek to increase lymphangiogenesis via induction of lymphangiogenic factors and inhibition of its antagonists. The resultant increased lymphatic flow coupled with other anti-inflammatory activities restores gut homeostasis.

Decreased Lymphangiogenic Activities and Genes Expression of Cord Blood Lymphatic Endothelial Progenitor Cells (VEGFR3+/Pod+/CD11b+ Cells) in Patient with Preeclampsia

The abnormal development or disruption of the lymphatic vasculature has been implicated in metabolic and hypertensive diseases. Recent evidence suggests that the offspring exposed to preeclampsia (PE) in utero are at higher risk of long-term health problems, such as cardiovascular and metabolic diseases in adulthood, owing to in utero fetal programming. We aimed to investigate lymphangiogenic activities in the lymphatic endothelial progenitor cells (LEPCs) of the offspring of PE. Human umbilical cord blood LEPCs from pregnant women with severe PE (n = 10) and gestationally matched normal pregnancies (n = 10) were purified with anti-vascular endothelial growth factor receptor 3 (VEGFR3)/podoplanin/CD11b microbeads using a magnetic cell sorter device. LEPCs from PE displayed significantly delayed differentiation and reduced formation of lymphatic endothelial cell (LEC) colonies compared with the LEPCs from normal pregnancies. LECs differentiated from PE-derived LEPCs exhibited decreased tube formation, migration, proliferation, adhesion, wound healing, and 3D-sprouting activities as well as increased lymphatic permeability through the disorganization of VE-cadherin junctions, compared with the normal pregnancy-derived LECs. In vivo, LEPCs from PE showed significantly reduced lymphatic vessel formation compared to the LEPCs of the normal pregnancy. Gene expression analysis revealed that compared to the normal pregnancy-derived LECs, the PE-derived LECs showed a significant decrease in the expression of pro-lymphangiogenic genes (GREM1, EPHB3, VEGFA, AMOT, THSD7A, ANGPTL4, SEMA5A, FGF2, and GBX2). Collectively, our findings demonstrate, for the first time, that LEPCs from PE have reduced lymphangiogenic activities in vitro and in vivo and show the decreased expression of pro-lymphangiogenic genes. This study opens a new avenue for investigation of the molecular mechanism of LEPC differentiation and lymphangiogenesis in the offspring of PE and subsequently may impact the treatment of long-term health problems such as cardiovascular and metabolic disorders of offspring with abnormal development of lymphatic vasculature.

Lymphatic drainage from bronchus-associated lymphoid tissue in tolerant lung allografts promotes peripheral tolerance

Tertiary lymphoid organs are aggregates of immune and stromal cells including high endothelial venules and lymphatic vessels that resemble secondary lymphoid organs and can be induced at nonlymphoid sites during inflammation. The function of lymphatic vessels within tertiary lymphoid organs remains poorly understood. During lung transplant tolerance, Foxp3+ cells accumulate in tertiary lymphoid organs that are induced within the pulmonary grafts and are critical for the local downregulation of alloimmune responses. Here, we showed that tolerant lung allografts could induce and maintain tolerance of heterotopic donor-matched hearts through pathways that were dependent on the continued presence of the transplanted lung. Using lung retransplantation, we showed that Foxp3+ cells egressed from tolerant lung allografts via lymphatics and were recruited into donor-matched heart allografts. Indeed, survival of the heart allografts was dependent on lymphatic drainage from the tolerant lung allograft to the periphery. Thus, our work indicates that cellular trafficking from tertiary lymphoid organs regulates immune responses in the periphery. We propose that these findings have important implications for a variety of disease processes that are associated with the induction of tertiary lymphoid organs.

Tertiary lymphoid tissue in early-stage IgG4-related tubulointerstitial nephritis incidentally detected with a tumor lesion of the ureteropelvic junction: a case report

Background

IgG4-related kidney disease causes renal impairment of unknown pathogenesis that may progress to kidney failure. Although ectopic germinal centers contribute to the pathogenesis of the head and neck lesions of IgG4-related disease, the presence of tertiary lymphoid tissue (TLT) containing germinal centers in IgG4-RKD has rarely been reported.

Case presentation

We report a 72-year-old Japanese man who had IgG4-related tubulointerstitial nephritis (TIN) with TLT formation incidentally detected in a resected kidney with mass lesion of IgG4-related ureteritis in the ureteropelvic junction. During follow-up for past surgical resection of a bladder tumor, renal dysfunction developed and a ureter mass was found in the right ureteropelvic junction, which was treated by nephroureterectomy after chemotherapy. Pathology revealed no malignancy but abundant IgG4-positive cell infiltration, obliterative phlebitis and storiform fibrosis, confirming the diagnosis of IgG4-related ureteritis. In the resected right kidney, lymphoplasmacytes infiltrated the interstitium with focal distribution in the renal subcapsule and around medium vessels without storiform fibrosis, suggesting the very early stage of IgG4-TIN. Lymphocyte aggregates were also detected at these sites and consisted of B, T, and follicular dendritic cells, indicating TLT formation. IgG4-positive cells infiltrated around TLTs.

Conclusions

Our case suggests that TLT formation is related with the development of IgG4-TIN and our analysis of distribution of TLT have possibility to elucidate IgG4-TIN pathophysiology.

Vasculature-Associated Lymphoid Tissue: A Unique Tertiary Lymphoid Tissue Correlates With Renal Lesions in Lupus Nephritis Mouse Model

Lupus nephritis (LN) is a common complication in young patients and the most predominant cause of glomerulonephritis. Infiltrating immune cells and presence of immunocomplexes in the kidney are hallmarks of LN, which is closely associated with renal lesions (RLs). However, their regulatory mechanism in the kidney remains unclear, which is valuable for prevention of RL development. Here, we show the development of vasculature-associated lymphoid tissue (VALT) in LN, which is related to renal inflammatory cytokines, indicating that VALT is a unique tertiary lymphoid tissue. Transcriptomic analysis revealed different chemokines and costimulatory molecules for VALT induction and organization. Vascular and perivascular structures showed lymphoid tissue organization through lymphorganogenic chemokine production. Transcriptional profile and intracellular interaction also demonstrated antigen presentation, lymphocyte activity, clonal expansion, follicular, and germinal center activity in VALT. Importantly, VALT size was correlated with infiltrating immune cells in kidney and RLs, indicating its direct correlation with the development of RLs. In addition, dexamethasone administration reduced VALT size. Therefore, inhibition of VALT formation would be a novel therapeutic strategy against LN.

Skin-Associated B Cells in the Pathogenesis of Cutaneous Autoimmune Diseases-Implications for Therapeutic Approaches

B lymphocytes are crucial mediators of systemic immune responses and are known to be substantial in the pathogenesis of autoimmune diseases with cutaneous manifestations. Amongst them are lupus erythematosus, dermatomyositis, systemic sclerosis and psoriasis, and particularly those driven by autoantibodies such as pemphigus and pemphigoid. However, the concept of autoreactive skin-associated B cells, which may reside in the skin and locally contribute to chronic inflammation, is gradually evolving. These cells are believed to differ from B cells of primary and secondary lymphoid organs and may provide additional features besides autoantibody production, including cytokine expression and crosstalk to autoreactive T cells in an antigen-presenting manner. In chronically inflamed skin, B cells may appear in tertiary lymphoid structures. Those abnormal lymph node-like structures comprise a network of immune and stromal cells possibly enriched by vascular structures and thus constitute an ideal niche for local autoimmune responses. In this review, we describe current considerations of different B cell subsets and their assumed role in skin autoimmunity. Moreover, we discuss traditional and B cell-associated approaches for the treatment of autoimmune skin diseases, including drugs targeting B cells (e.g., CD19- and CD20-antibodies), plasma cells (e.g., proteasome inhibitors, CXCR4 antagonists), activated pathways (such as BTK- and PI3K-inhibitors) and associated activator molecules (BLyS, APRIL).

AGTR1 promotes lymph node metastasis in breast cancer by upregulating CXCR4/SDF-1α and inducing cell migration and invasion

The angiotensin II type I receptor (AGTR1) has a strong influence on tumor growth, angiogenesis, inflammation and immunity. However, the role of AGTR1 on lymph node metastasis (LNM) in breast cancer, which correlates with tumor progression and patient survival, has not been examined. AGTR1 was highly expressed in lymph node-positive tumor tissues, which was confirmed by the Oncomine database. Next, inhibition of AGTR1 reduced tumor growth and LNM in orthotopic xenografts by bioluminescence imaging (BLI). Losartan, an AGTR1-specific inhibitor, decreased the chemokine pair CXCR4/SDF-1α levels in vivo and inhibited AGTR1-induced cell migration and invasion in vitro. Finally, the molecular mechanism of AGTR1-induced cell migration and LNM was assessed by knocking down AGTR1 in normal cells or CXCR4 in AGTR1^high cells. AGTR1-silenced cells treated with losartan showed lower CXCR4 expression. AGTR1 overexpression caused the upregulation of FAK/RhoA signaling molecules, while knocking down CXCR4 in AGTR1^high cells downregulated these molecules. Collectively, AGTR1 promotes LNM by increasing the chemokine pair CXCR4/SDF-1α and tumor cell migration and invasion. The potential mechanism of AGTR1-mediated cell movement relies on activating the FAK/RhoA pathway. Our study indicated that inhibiting AGTR1 may be a potential therapeutic target for LNM in early-stage breast cancer.

12-Chemokine signature, a predictor of tumor recurrence in colorectal cancer

Tertiary lymphoid structures (TLSs) provide an immunological antineoplastic effect. Recent evidences link a unique 12-chemokine (CCL2, -3, -4, -5, -8, -18, -19, -21, CXCL9, -10, -11, -13) signature status from tumor tissue and the TLS expression. However, the potential significance of 12-chemokine signature status for clinical use is unknown. We aimed to evaluate the association of 12-chemokine signature status with patient outcomes in colorectal cancer (CRC). We used integrated data of resected 975 CRC cases within three independent cohorts from France, Japan and the United States (GSE39582, KUMAMOTO from Kumamoto university hospital and TCGA). The association of 12-chemokine signature status with clinicopathological features, patient outcome, TLS expression status and key tumor molecular features was analyzed. Patients with low 12-chemokine signature status had a significant shorter relapse-free survival in discovery cohort (HR: 1.61, 95% CI: 1.11-2.39, p = 0.0123), which was confirmed in validation cohort (HR: 3.31, 95% CI: 1.33-10.08, p = 0.0087). High 12-chemokine signature status had significant associations with right-sided tumor, high tumor-localized TLS expression, BRAF mutant, CIMP-high status and MSI-high status. Furthermore, RNA-seq based analysis showed that high 12-chemokine signature status was strongly associated with inflammation-related, immune cells-related and apoptosis pathways (using gene set enrichment analysis), and more tumor-infiltrating immune cells, such as cytotoxic T lymphocytes and myeloid dendritic cells (using MCP-counter analysis). We investigated a promising effect of 12-chemokine signature status in CRC patients who underwent resection. Our data may be helpful in developing novel immunological treatment strategies for CRC.

Nonproliferative and Proliferative Lesions of the Rat and Mouse Hematolymphoid System

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative changes in rats and mice. The purpose of this publication is to provide a standardized nomenclature for classifying changes observed in the hematolymphoid organs, including the bone marrow, thymus, spleen, lymph nodes, mucosa-associated lymphoid tissues, and other lymphoid tissues (serosa-associated lymphoid clusters and tertiary lymphoid structures) with color photomicrographs illustrating examples of the lesions. Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. The nomenclature for these organs is divided into 3 terminologies: descriptive, conventional, and enhanced. Three terms are listed for each diagnosis. The rationale for this approach and guidance for its application to toxicologic pathology are described in detail below.

Aging Induces an Nlrp3 Inflammasome-Dependent Expansion of Adipose B Cells That Impairs Metabolic Homeostasis

During aging, visceral adiposity is often associated with alterations in adipose tissue (AT) leukocytes, inflammation, and metabolic dysfunction. However, the contribution of AT B cells in immunometabolism during aging is unexplored. Here, we show that aging is associated with an expansion of a unique population of resident non-senescent aged adipose B cells (AABs) found in fat-associated lymphoid clusters (FALCs). AABs are transcriptionally distinct from splenic age-associated B cells (ABCs) and show greater expansion in female mice. Functionally, whole-body B cell depletion restores proper lipolysis and core body temperature maintenance during cold stress. Mechanistically, the age-induced FALC formation, AAB, and splenic ABC expansion is dependent on the Nlrp3 inflammasome. Furthermore, AABs express IL-1R, and inhibition of IL-1 signaling reduces their proliferation and increases lipolysis in aging. These data reveal that inhibiting Nlrp3-dependent B cell accumulation can be targeted to reverse metabolic impairment in aging AT.

The Role of Endothelial Cells and TNF-Receptor Superfamily Members in Lymphoid Organogenesis and Function During Health and Inflammation

Lymph nodes (LNs) are crucial for the orchestration of immune responses. LN reactions depend on interactions between incoming and local immune cells, and stromal cells. To mediate these cellular interactions an organized vascular network within the LN exists. In general, the LN vasculature can be divided into two components: blood vessels, which include the specialized high endothelial venules that recruit lymphocytes from the bloodstream, and lymphatic vessels. Signaling via TNF receptor (R) superfamily (SF) members has been implicated as crucial for the development and function of LNs and the LN vasculature. In recent years the role of cell-specific signaling of TNFRSF members in different endothelial cell (EC) subsets and their roles in development and maintenance of lymphoid organs has been elucidated. Here, we discuss recent insights into EC-specific TNFRSF member signaling and highlight its importance in different EC subsets in LN organogenesis and function during health, and in lymphocyte activation and tertiary lymphoid structure formation during inflammation.

Immunology of the ageing kidney

Immunosenescence involves a series of ageing-induced alterations in the immune system and is characterized by two opposing hallmarks: defective immune responses and increased systemic inflammation. The immune system is modulated by intrinsic and extrinsic factors and undergoes profound changes in response to the ageing process. Immune responses are therefore highly age-dependent. Emerging data show that immunosenescence underlies common mechanisms responsible for several age-related diseases and is a plastic state that can be modified and accelerated by non-heritable environmental factors and pharmacological intervention. In the kidney, resident macrophages and fibroblasts are continuously exposed to components of the external environment, and the effects of cellular reprogramming induced by local immune responses, which accumulate with age, might have a role in the increased susceptibility to kidney disease among elderly individuals. Additionally, because chronic kidney disease, especially end-stage renal disease, is often accompanied by immunosenescence, which affects these patients independently of age, and many kidney diseases are strongly age-associated, treatment approaches that target immunosenescence might be particularly clinically relevant.

A potential role of toll-like receptors, IFN-γ and the phosphatidylinositol 3-kinase pathway in the pathogenesis of acquired mediastinal lymphatic malformation

Sarcoidosis is a multisystem disorder with non-caseating granulomas in various organs. The etiology of sarcoid granuloma formation is not clear and likely an antigen-induced process. We came across a previously treated sarcoidosis patient who presented with worsening dyspnea on exertion for several months and several days of difficulty swallowing. On Chest CT imaging, large posterior mediastinal mass was found that subsequently diagnosed as macrocystic lymphatic malformation after surgical resection. Pathophysiology of development of acquired lymphatic malformations in a sarcoidosis patient is currently not clear. We hypothesize there might be a complex interplay of Toll-like receptors, IFN-γ and the phosphatidylinositol 3-kinase pathway in the pathogenesis.

Adipose Tissue: A Tertiary Lymphoid Organ: Does It Change with Age?

In this manuscript, we summarize published results showing that obesity and aging are inflammatory conditions associated with serious health problems, increased risk for disease and death. We show that fat mass increases with age and represents a major contributor to insulin resistance and the metabolic syndrome. We summarize the effects of age on the adipose tissue (AT), related to the abundance, distribution, cellular composition, endocrine signaling and function of the tissue. The AT is an immunological tissue, with several hallmarks of innate and adaptive immune responses. We show that in both mice and humans, the AT is heavily infiltrated by immune cells that have receptors for pro-inflammatory cytokines and chemokines secreted by the adipocytes and also by the immune cells that have infiltrated the AT. We also show that the AT provides an environment for the secretion of IgG antibodies with anti-self (autoimmune) reactivity. As we have previously shown, this is due to the release of self antigens following cell death due to hypoxia, as well as to the expression of activation-induced cytidine deaminase, the enzyme of class switch recombination, and the transcription factor T-bet by the resident B cells, which also express the membrane marker CD11c, both involved in the production of autoimmune IgG antibodies. We show data in support of the AT as a tertiary lymphoid organ (TLO), showing the examples of TLOs that develop within the AT, such as fat-associated lymphoid clusters and milky spots, as well as artery TLOs that develop in the adventitia areas of the aorta.

High endothelial venules are associated with microsatellite instability, hereditary background and immune evasion in colorectal cancer

BACKGROUND

Microsatellite-unstable (MSI) tumours show a high load of mutational neoantigens, as a consequence of DNA mismatch repair deficiency. Consequently, MSI tumours commonly present with dense immune infiltration and develop immune evasion mechanisms. Whether improved lymphocyte recruitment contributes to the pronounced immune infiltration in MSI tumours is unknown. We analysed the density of high endothelial venules (HEV) and postcapillary blood vessels specialised for lymphocyte trafficking, in MSI colorectal cancers (CRC).

METHODS

HEV density was determined by immunohistochemical staining of FFPE tissue sections from MSI (n = 48) and microsatellite-stable (MSS, n = 35) CRCs. Associations with clinical and pathological variables were analysed.

RESULTS

We found elevated HEV densities in MSI compared with MSS CRCs (median 0.049 vs 0.000 counts/mm2, respectively, p = 0.0002), with the highest densities in Lynch syndrome MSI CRCs. Dramatically elevated HEV densities were observed in B2M-mutant Lynch syndrome CRCs, pointing towards a link between lymphocyte recruitment and immune evasion (median 0.485 vs 0.0885 counts/mm2 in B2M-wild-type tumours, p = 0.0237).

CONCLUSIONS

Our findings for the first time indicate a significant contribution of lymphocyte trafficking in immune responses against MSI CRC, particularly in the context of Lynch syndrome. High HEV densities in B2M-mutant tumours underline the significance of immunoediting during tumour evolution.

Therapeutic delivery to the peritoneal lymphatics: Current understanding, potential treatment benefits and future prospects

The interest in approaches to deliver therapeutics to the lymphatic system has increased in recent years as the lymphatics have been discovered to play an important role in a range of disease states such as cancer metastases, inflammatory and metabolic disease, and acute and critical illness. Therapeutic delivery to lymph has the potential to enhance treatment of these conditions. Currently much of the existing data explores therapeutic delivery to the lymphatic vessels and nodes that drain peripheral tissues and the intestine. Relatively little focus has been given to understanding the anatomy, function and therapeutic delivery to the peritoneal lymphatics. Gaining a better understanding of peritoneal lymphatic structure and function would contribute to the understanding of disease processes involving these lymphatics and facilitate the development of delivery systems to target therapeutics to the peritoneal lymphatics. This review explores the basic anatomy and ultrastructure of the peritoneal lymphatics system, the lymphatic drainage pathways from the peritoneum, and therapeutic and delivery system characteristics (size, lipophilicity and surface properties) that favour lymph uptake and retention after intraperitoneal delivery. Finally, techniques that can be used to quantify uptake into peritoneal lymph are outlined, providing a platform for future studies.

Tumor progression mechanisms: Insights from the central immune regulation of tissue homeostasis

Knowledge of the mechanisms underlying the spread of cancer at the cellular and molecular levels is expanding rapidly. However, the central regulators governing the initiation and the rate of tumor growth remain poorly established. The fundamental principles of innate and adaptive immunity may explain how immune cells generate a specific response to tumor tissue. In the current review, the functional features of the immune system that contribute to the maintenance of normal tissue homeostasis, as well as their disruption in malignant transformations, were analyzed. Experimental and clinical studies previously demonstrated the involvement of regulatory T-cells in the process of tumor metastasis in a tissue-specific manner. An understanding of the cross talk between lymphoid and tumor cells may provide an insight into cancer evolution in terms of the mechanisms of T-cell competency formation. Elucidating the mechanisms of tumor progression via central immune regulation has implications for the development of novel therapeutic agents that target immune checkpoints.

Vascular Endothelial Growth Factor-D (VEGF-D) Overexpression and Lymphatic Expansion in Murine Adipose Tissue Improves Metabolism in Obesity

Obese adipose tissue expansion is an inflammatory process that results in dysregulated lipolysis, increased circulating lipids, ectopic lipid deposition, and systemic insulin resistance. Lymphatic vessels provide a route of fluid, macromolecule, and immune cell clearance, and lymphangiogenesis increases this capability. Indeed, inflammation-associated lymphangiogenesis is critical in resolving acute and chronic inflammation, but it is largely absent in obese adipose tissue. Enhancing adipose tissue lymphangiogenesis could, therefore, improve metabolism in obesity. To test this hypothesis, transgenic mice with doxycycline-inducible expression of murine vascular endothelial growth factor (VEGF)-D under a tightly controlled Tet-On promoter were crossed with adipocyte-specific adiponectin-reverse tetracycline-dependent transactivator mice (Adipo-VD) to stimulate adipose tissue-specific lymphangiogenesis during 16-week high-fat diet-induced obesity. Adipose VEGF-D overexpression induced de novo lymphangiogenesis in murine adipose tissue, and obese Adipo-VD mice exhibited enhanced glucose clearance, lower insulin levels, and reduced liver triglycerides. On β-3 adrenergic stimulation, Adipo-VD mice exhibited more rapid and increased glycerol flux from adipose tissue, suggesting that the lymphatics are a potential route of glycerol clearance. Resident macrophage crown-like structures were scarce and total F4/80⁺ macrophages were reduced in obese Adipo-VD s.c. adipose tissue with evidence of increased immune trafficking from the tissue. Augmenting VEGF-D signaling and lymphangiogenesis specifically in adipose tissue, therefore, reduces obesity-associated immune accumulation and improves metabolic responsiveness.

The role of stroma and epithelial cells in primary Sjögren's syndrome

Primary SS (pSS) is a chronic autoimmune condition characterized by infiltration of the exocrine glands and systemic B cell hyperactivation. This glandular infiltration is associated with loss of glandular function, with pSS patients primarily presenting with severe dryness of the eyes and mouth. Within the affected glands, the infiltrating lymphocytes are organized in tertiary lymphoid structures. Tertiary lymphoid structures subvert normal tissue architecture and impact on organ function, by promoting the activation and maintenance of autoreactive lymphocytes. This review summarizes the current knowledge about the role of stromal cells (including endothelium, epithelium, nerves and fibroblasts) in the pathogenesis of pSS, in particular the interactions taking place between stromal cells and infiltrating lymphocytes. We will provide evidences pointing towards the driving role of stromal cells in the orchestration of the local inflammatory milieu, thus highlighting the need for therapies aimed at targeting this compartment alongside classical immunosuppression in pSS.

Deconstructing Immune Microenvironments of Lymphoid Tissues for Reverse Engineering

The immune microenvironment presents a diverse panel of cues that impacts immune cell migration, organization, differentiation, and the immune response. Uniquely, both the liquid and solid phases of every specific immune niche within the body play an important role in defining cellular functions in immunity at that particular location. The in vivo immune microenvironment consists of biomechanical and biochemical signals including their gradients, surface topography, dimensionality, modes of ligand presentation, and cell-cell interactions, and the ability to recreate these immune biointerfaces in vitro can provide valuable insights into the immune system. This manuscript reviews the critical roles played by different immune cells and surveys the current progress of model systems for reverse engineering of immune microenvironments with a focus on lymphoid tissues.

Lymphatic Vessel Network Structure and Physiology

The lymphatic system is comprised of a network of vessels interrelated with lymphoid tissue, which has the holistic function to maintain the local physiologic environment for every cell in all tissues of the body. The lymphatic system maintains extracellular fluid homeostasis favorable for optimal tissue function, removing substances that arise due to metabolism or cell death, and optimizing immunity against bacteria, viruses, parasites, and other antigens. This article provides a comprehensive review of important findings over the past century along with recent advances in the understanding of the anatomy and physiology of lymphatic vessels, including tissue/organ specificity, development, mechanisms of lymph formation and transport, lymphangiogenesis, and the roles of lymphatics in disease. © 2019 American Physiological Society. Compr Physiol 9:207-299, 2019.

Mast cells in early rheumatoid arthritis associate with disease severity and support B cell autoantibody production

OBJECTIVES

Mast cells (MCs) are involved in the pathogenesis of rheumatoid arthritis (RA). However, their contribution remains controversial. To establish their role in RA, we analysed their presence in the synovium of treatment-naïve patients with early RA and their association and functional relationship with histological features of synovitis.

METHODS

Synovial tissue was obtained by ultrasound-guided biopsy from treatment-naïve patients with early RA (n=99). Immune cells (CD3/CD20/CD138/CD68) and their relationship with CD117+MCs in synovial tissue were analysed by immunohistochemistry (IHC) and immunofluorescence (IF). The functional involvement of MCs in ectopic lymphoid structures (ELS) was investigated in vitro, by coculturing MCs with naïve B cells and anticitrullinated protein antibodies (ACPA)-producing B cell clones, and in vivo in interleukin-27 receptor alpha (IL27ra)-deficient and control mice during antigen-induced arthritis (AIA).

RESULTS

High synovial MC counts are associated with local and systemic inflammation, autoantibody positivity and high disease activity. IHC/IF showed that MCs reside at the outer border of lymphoid aggregates. Furthermore, human MCs promote the activation and differentiation of naïve B cells and induce the production of ACPA, mainly via contact-dependent interactions. In AIA, synovial MC numbers increase in IL27ra deficient mice, in association with ELS and worse disease activity.

CONCLUSIONS

Synovial MCs identify early RA patients with a severe clinical form of synovitis characterised by the presence of ELS.

Molecular patterns of cancer colonisation in lymph nodes of breast cancer patients

Lymph node (LN) metastasis is an important prognostic parameter in breast carcinoma, a crucial site for tumour–immune cell interaction and a gateway for further dissemination of tumour cells to other metastatic sites. To gain insight into the underlying molecular changes from the pre-metastatic, via initial colonisation to the fully involved LN, we reviewed transcriptional research along the evolving microenvironment of LNs in human breast cancers patients. Gene expression studies were compiled and subjected to pathway-based analyses, with an emphasis on immune cell-related genes. Of 366 studies, 14 performed genome-wide gene expression comparisons and were divided into six clinical-biological scenarios capturing different stages of the metastatic pathway in the LN, as follows: metastatically involved LNs are compared to their patient-matched primary breast carcinomas (scenario 1) or the normal breast tissue (scenario 2). In scenario 3, uninvolved LNs were compared between LN-positive patients and LN-negative patients. Scenario 4 homed in on the residual uninvolved portion of involved LNs and compared it to the patient-matched uninvolved LNs. Scenario 5 contrasted uninvolved and involved LNs, whilst in scenario 6 involved (sentinel) LNs were assessed between patients with other either positive or negative LNs (non-sentinel).

Gene lists from these chronological steps of LN metastasis indicated that gene patterns reflecting deficiencies in dendritic cells and hyper-proliferation of B cells parallel to tumour promoting pathways, including cell adhesion, extracellular matrix remodelling, cell motility and DNA repair, play key roles in the changing microenvironment of a pro-metastatic to a metastatically involved LN. Similarities between uninvolved LNs and the residual uninvolved portion of involved LNs hinted that LN alterations expose systemic tumour-related immune responses in breast cancer patients. Despite the diverse settings, gene expression patterns at different stages of metastatic colonisation in LNs were recognised and may provide potential avenues for clinical interventions to counteract disease progression for breast cancer patients.

Advances in T follicular helper and T follicular regulatory cells in transplantation immunity

B cells play a crucial role in alloreactivity of organ transplant rejection and graft versus host diseases (GVHD). Over the past decade, it has been well recognized that B-cell infiltration in allografts and de novo donor-specific antibodies (DSA) were strongly associated with severe graft rejection and loss, as well as glucocorticoid resistance. Emerging evidence has demonstrated that Follicular T helper (Tfh) cells are key effectors to promote the proliferation and differentiation of B cells into antibody-producing plasmablasts and memory B cells. T-follicular regulatory (Tfr) cells are a recently recognized cell population that has a negative regulatory role on Tfh cells in the follicle, preventing incessant antibody production. It is still less clear how those humoral immunoreactive cells affect transplant rejection and allograft loss. This review focuses on the production and function of Tfr/Tfh cells in the transplant environment. Better understanding of the functions and mechanisms of Tfr/Tfh cells will help to design new strategies to prevent allograft rejection and prolong graft survival.

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.

Serum biomarker for diagnostic evaluation of pulmonary arterial hypertension in systemic sclerosis

Background

Systemic sclerosis-associated pulmonary arterial hypertension (SSc-PAH) is one of the leading causes of death in SSc. Identification of a serum-based proteomic diagnostic biomarker for SSc-PAH would allow for rapid non-invasive screening and could positively impact patient survival. Identification and validation of novel proteins could potentially facilitate the identification of SSc-PAH, and might also point to important protein mediators in pathogenesis.

Methods

Thirteen treatment-naïve SSc-PAH patients had serum collected at time of diagnosis and were used as the discovery cohort for the protein-expression biomarker. Two proteins, Midkine and Follistatin-like 3 (FSTL3) were then validated by enzyme-linked immunosorbent assays. Midkine and FSTL3 were tested in combination to identify SSc-PAH and were validated in two independent cohorts of SSc-PAH (n = 23, n = 11).

Results

Eighty-two proteins were found to be differentially regulated in SSc-PAH sera. Two proteins (Midkine and FSTL3) were also shown to be elevated in publicly available data and their expression was evaluated in independent cohorts. In the validation cohorts, the combination of Midkine and FSTL3 had an area under the receiver operating characteristic curve (AUC) of 0.85 and 0.92 with respective corresponding measures of sensitivity of 76% and 91%, and specificity measures of 76% and 80%.

Conclusions

These findings indicate that there is a clear delineation between overall protein expression in sera from SSc patients and those with SSc-PAH. The combination of Midkine and FSTL3 can serve as an SSc-PAH biomarker and are potential drug targets for this rare disease population.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1679-8) contains supplementary material, which is available to authorized users.

Physiological Perspective on Therapies of Lymphatic Vessels

Significance: Growth of distinctive blood vessels of granulation tissue is a central step in the post-developmental tissue remodeling. Even though lymphangiogenesis is a part of the regeneration process, the significance of the controlled restoration of lymphatic vessels has only recently been recognized.

Recent Advances: Identification of lymphatic markers and growth factors paved the way for the exploration of the roles of lymphatic vessels in health and disease. Emerging pro-lymphangiogenic therapies use vascular endothelial growth factor (VEGF)-C to combat fluid retention disorders such as lymphedema and to enhance the local healing process.

Critical Issues: The relevance of recently identified lymphatic functions awaits verification by their association with pathologic conditions. Further, despite a century of research, the complete etiology of secondary lymphedema, a fluid retention disorder directly linked to the lymphatic function, is not understood. Finally, the specificity of pro-lymphangiogenic therapy depends on VEGF-C transfection efficiency, dose exposure, and the age of the subject, factors that are difficult to standardize in a heterogeneous human population.

Future Directions: Further research should reveal the role of lymphatic circulation in internal organs and connect its impairment with human diseases. Pro-lymphangiogenic therapies that aim at the acceleration of tissue healing should focus on the controlled administration of VEGF-C to increase their capillary specificity, whereas regeneration of collecting vessels might benefit from balanced maturation and differentiation of pre-existing lymphatics. Unique features of pre-nodal lymphatics, fault tolerance and functional hyperplasia of capillaries, may find applications outreaching traditional pro-lymphangiogenic therapies, such as immunomodulation or enhancement of subcutaneous grafting.

Effect of cryopreservation on lymph node fragment regeneration after autologous transplantation in the minipig model

Introduction

Lymphoedema is a worldwide pandemic causing swelling of tissues due to dysfunctional transport of lymph fluid. Present management concepts are based in conservative palliation of symptoms through manual lymphatic drainage, use of compression garments, manual lymph drainage, exercise, and skin care. Nevertheless, some curative options as autologous lymph node transplantation were shown to reduce lymphoedema in selected cases. Lately, some concern has arisen due to reports of donor site morbidity. A possible solution could be the development of artificial lymph node scaffolds as niches of lymphatic regeneration. Engineering these scaffolds has included cryopreservation of lymph node stroma. However, the effects of cryopreservation on the regeneration capacities of these organs were unknown.

Materials and methods

Here, we used the minipig animal model to assess lymphatic regeneration processes after cryopreservation of autologous lymph nodes. Superficial inguinal lymph nodes were excised and conserved at -80°C for 1 month. Thereafter, lymph node fragments were transplanted in the subcutaneous tissue.

Results

Regeneration of the lymph nodes was assessed five months after transplantation. We show that lymph node fragment regeneration takes place in spite of former cryopreservation. Transplanted fragments presented typical histological appearance. Their draining capacity was documented by macroscopic transport of Berlin Blue dye as well as through SPECT-CT hybrid imaging.

Discussion

In conclusion, our results suggest that processes of cryopreservation can be used in the creation of artificial lymph node scaffolds without major impairment of lymph node fragments regeneration.

The expansion in lymphoid organs of IL-4+ BATF+ T follicular helper cells is linked to IgG4 class switching in vivo

Distinct T follicular helper (T_FH) subsets that influence specific class-switching events are assumed to exist, but the accumulation of isotype-specific T_FH subsets in secondary lymphoid organs (SLOs) and tertiary lymphoid organs has not been hitherto demonstrated. IL-4-expressing T_FH cells are surprisingly sparse in human SLOs. In contrast, in IgG4-related disease (IgG4-RD), a disorder characterized by polarized Ig class switching, most T_FH cells in tertiary and SLOs make IL-4. Human IL-4⁺ T_FH cells do not express GATA-3 but express nuclear BATF, and the transcriptomes of IL-4-secreting T_FH cells differ from both PD1^hi T_FH cells that do not secrete IL-4 and IL-4-secreting non-T_FH cells. Unlike IgG4-RD, IL-4⁺ T_FH cells are rarely found in tertiary lymphoid organs in Sjögren's syndrome, a disorder in which IgG4 is not elevated. The proportion of CD4⁺IL-4⁺BATF⁺ T cells and CD4⁺IL-4⁺CXCR5⁺ T cells in IgG4-RD tissues correlates tightly with tissue IgG4 plasma cell numbers and plasma IgG4 levels in patients but not with the total plasma levels of other isotypes. These data describe a disease-related T_FH subpopulation in human tertiary lymphoid organs and SLOs that is linked to IgG4 class switching.

Lymphotoxin β receptor-mediated NFκB signaling promotes glial lineage differentiation and inhibits neuronal lineage differentiation in mouse brain neural stem/progenitor cells

BACKGROUND

Lymphotoxin (LT) is a lymphokine mainly expressed in lymphocytes. LTα binds one or two membrane-associated LTβ to form LTα2β1 or LTα1β2 heterotrimers. The predominant LTα1β2 binds to LTβ receptor (LTβR) primarily expressed in epithelial and stromal cells. Most studies on LTβR signaling have focused on the organization, development, and maintenance of lymphoid tissues. However, the roles of LTβR signaling in the nervous system, particularly in neurogenesis, remain unknown. Here, we investigated the role of LTβR-mediated NFκB signaling in regulating neural lineage differentiation.

METHODS

The C57BL/6J wild-type and GFAP-dnIκBα transgenic mice were used. Serum-free embryoid bodies were cultured from mouse embryonic stem cells and further induced into neural stem/progenitor cells (NSCs/NPCs). Primary neurospheres were cultured from embryonic and adult mouse brains followed by monolayer culture for amplification/passage. NFκB activation was determined by adenovirus-mediated NFκB-firefly-luciferase reporter assay and p65/RelB/p52 nuclear translocation assay. LTβR mRNA expression was evaluated by quantitative RT-PCR and LTβR protein expression was determined by immunohistochemistry and Western blot analysis. Multilabeled immunocytochemistry or immunohistochemistry followed by fluorescent confocal microscopy and quantitative analysis of neural lineage differentiation were performed. Graphing and statistical analysis were performed with GraphPad Prism software.

RESULTS

In cultured NSCs/NPCs, LTα1β2 stimulation induced an activation of classical and non-classical NFκB signaling. The expression of LTβR-like immunoreactivity in GFAP+/Sox2+ NSCs was identified in well-established neurogenic zones of adult mouse brain. Quantitative RT-PCR and Western blot analysis validated the expression of LTβR in cultured NSCs/NPCs and brain neurogenic regions. LTβR expression was significantly increased during neural induction. LTα1β2 stimulation in cultured NSCs/NPCs promoted astroglial and oligodendrocytic lineage differentiation, but inhibited neuronal lineage differentiation. Astroglial NFκB inactivation in GFAP-dnIκBα transgenic mice rescued LTβR-mediated abnormal phenotypes of cultured NSCs/NPCs.

CONCLUSION

This study provides the first evidence for the expression and function of LTβR signaling in NSCs/NPCs. Activation of LTβR signaling promotes glial lineage differentiation. Our results suggest that neurogenesis is regulated by the adaptive immunity and inflammatory responses.

Indocyanine green nanoparticles undergo selective lymphatic uptake, distribution and retention and enable detailed mapping of lymph vessels, nodes and abnormalities

The distributed network of lymph vessels and nodes in the body, with its complex architecture and physiology, presents a major challenge for whole-body lymphatic-targeted drug delivery. To gather physiological and pathological information of the lymphatics, near-infrared (NIR) fluorescence imaging of NIR fluorophores is used in clinical practice due to its tissue-penetrating optical radiation (700-900 nm) that safely provides real-time high-resolution in vivo images. However, indocyanine green (ICG), a common clinical NIR fluorophore, is unstable in aqueous environments and under light exposure, and its poor lymphatic distribution and retention limits its use as a NIR lymphatic tracer. To address this, we investigated in mice the distribution pathways of a novel nanoparticle formulation that stabilises ICG and is optimised for lymphatic drug delivery. From the subcutaneous space, ICG particles provided selective lymphatic uptake, lymph vessel and node retention, and extensive first-pass lymphatic distribution of ICG, enabling 0.2 mm and 5-10 cell resolution of lymph vessels, and high signal-to-background ratios for lymphatic vessel and node networks. Soluble (free) ICG readily dissipated from lymph vessels local to the injection site and absorbed into the blood. These unique characteristics of ICG particles could enable mechanistic studies of the lymphatics and diagnosis of lymphatic abnormalities.

Meningeal Immunity, Drainage, and Tertiary Lymphoid Structure Formation

For decades, the brain has been considered an immune-privileged organ, meaning that the brain was mainly ignored by the immune system and that the presence of immune cells, notably of the adaptive arm, was a hallmark of pathological conditions. Over the past few decades, the definition of the immune privilege continues to be refined. There has been evidence accumulating that shows that the immune system plays a role in proper brain function. This evidence may represent an effective source of therapeutic targets for neurological disorders. In this chapter, we discuss the recent advances in understanding the immunity of the brain and describe how tertiary lymphoid structures can be generated in the central nervous system, which might represent a new avenue to treat neurological disorders.

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.

S1P Provokes Tumor Lymphangiogenesis via Macrophage-Derived Mediators Such as IL-1β or Lipocalin-2

A pleiotropic signaling lipid, sphingosine-1-phosphate (S1P), has been implicated in various pathophysiological processes supporting tumor growth and metastasis. However, there are only a few descriptive studies suggesting a role of S1P in tumor lymphangiogenesis, which is critical for tumor growth and dissemination. Corroborating own data, the literature suggests that apoptotic tumor cell-derived S1P alters the phenotype of tumor-associated macrophages (TAMs) to gain protumor functions. However, mechanistically, the role of TAM-induced lymphangiogenesis has only been poorly described, mostly linked to the production of lymphangiogenic factors such as vascular endothelial growth factor C (VEGF-C) and VEGF-D, or transdifferentiation into lymphatic endothelial cells. Recent findings highlight a rather underappreciated role of S1P in tumor lymphangiogenesis, referring to the production of interleukin-1β (IL-1β) and lipocalin-2 (LCN2) by a tumor-promoting macrophage phenotype. In this review, we aim to provide to the readers with the current understanding of the molecular mechanism how apoptotic cell-derived S1P triggers TAMs to promote lymphangiogenesis.

Distinct Distribution of Immunocytes in a Retropharyngeal Lymphadenopathy Associated with Kawasaki Disease: A Case Study Compared with Tonsillitis

OBJECTIVES

Retropharyngeal lesions are often associated with Kawasaki disease (KD). A 4-year-old male first presented a peritonsillar and retropharyngeal abscess-like lesion. Surgical tonsillectomy was performed to avoid a risk of mediastinal abscess, but he fulfilled the diagnostic criteria of KD after the operation. This prompted us to perform a histological study on the KD tonsils.

METHODS

The histopathology of the KD tonsil specimens were compared with hypertrophic tonsils obtained from 4 patients with chronic tonsillitis unrelated to KD assessed by the immunostainings.

RESULTS

KD tonsils showed small lymphatic follicles and neutrophil infiltration in the peritonsillar muscle layer, with no evidence of vasculitis or abscess formation. The KD tonsils exclusively showed (1) predominant activated CD4+ T cells in the perifollicular interstitium, (2) sparse scattering of CD68+ monocytes/macrophages in the lymphatic follicles, and (3) polyclonal carcinoembryonic antigen-positive cells in the lymphatic follicles and venules with the high endothelial cells.

CONCLUSIONS

The uniquely distributed immunocytes suggest the inflammatory process of KD involving the pathogen-associated molecules.

Tbet and IL-36γ cooperate in therapeutic DC-mediated promotion of ectopic lymphoid organogenesis in the tumor microenvironment

We have previously reported that direct injection of dendritic cells (DC) engineered to express the Type-1 transactivator Tbet (i.e., DC.Tbet) into murine tumors results in antitumor efficacy in association with the development of structures resembling tertiary lymphoid organs (TLO) in the tumor microenvironment (TME). These TLO contained robust infiltrates of B cells, DC, NK cells, and T cells in proximity to PNAd⁺ blood vessels; however, they were considered incomplete, since the recruited B cells failed to organize into classic germinal center-like structures. We now report that antitumor efficacy and TLO-inducing capacity of DC.Tbet-based i.t. therapy is operational in peripheral lymph node-deficient LTA^-/- mice, and that it is highly dependent upon a direct Tbet target gene product, IL-36γ/IL-1F9. Intratumoral DC.Tbet fails to provide protection to tumor-bearing IL-36R^-/- hosts, or to tumor-bearing wild-type recipient mice co-administered rmIL-1F5/IL-36RN, a natural IL-36R antagonist. Remarkably, the injection of tumors with DC engineered to secrete a bioactive form of mIL-36γ (DC.IL36γ) also initiated therapeutic TLO and slowed tumor progression in vivo. Furthermore, DC.IL36γ cells strongly upregulated their expression of Tbet, suggesting that Tbet and IL-36γ cooperate to reinforce each other's expression in DC, rendering them competent to promote TLO formation in an "immunologically normalized," therapeutic TME.