Tertiary lymphoid organs are associated with the progression of kidney damage and regulated by interleukin-17A

The PP2A inhibitor LB-100 mitigates lupus nephritis by suppressing tertiary lymphoid structure formation

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multi-organ involvement and autoantibody production. Patients with SLE face a substantial risk of developing lupus nephritis (LN), which imposes a substantial burden on both patients and their families. Protein phosphatase 2A (PP2A) is a widely distributed serine/threonine phosphatase that participates in regulating multiple signaling pathways. Inhibition of PP2A has been implicated in the treatment of various diseases. LB-100, a small molecule inhibitor of PP2A, has demonstrated anti-tumor therapeutic effects and high safety profile in preclinical experiments. However, the role of PP2A and its inhibitor has been insufficiently studied in LN. In this study, we assessed the potential effects of LB-100 in both MRL/lpr mice and R848-induced BALB/c mice. Our findings indicated that LB-100 administration led to reduced spleen enlargement, decreased deposition of immune complexes, ameliorated renal damage, and improved kidney function in both spontaneous and R848-induced lupus mouse models. Importantly, we observed the formation of tertiary lymphoid structures (TLSs) in the kidneys of two distinct lupus mouse models. The levels of signature genes of TLS were elevated in the kidneys of lupus mice, whereas LB-100 mitigated chemokine production and inhibited TLS formation. In addition, we confirmed that inhibition or knockdown of PP2A reduced the production of T cell-related chemokines by renal tubular epithelial cells (RTEC). In summary, our study highlighted the renal protective potential of the PP2A inhibitor LB-100 in two distinct lupus mouse models, suggesting its potential as a novel strategy for treating LN and other autoimmune diseases.

Prognostic and therapeutic monitoring value of plasma and urinary cytokine profile in primary membranous nephropathy: the STARMEN trial cohort

Background

Primary membranous nephropathy (PMN) is usually caused by anti-phospholipase A2 receptor (PLA2R) autoantibodies. There are different therapeutic options according to baseline risk. Novel biomarkers are needed to optimize risk stratification and predict and monitor the response to therapy, as proteinuria responses may be delayed. We hypothesized that plasma or urinary cytokines may provide insights into the course and response to therapy in PMN.

Methods

Overall, 192 data points from 34 participants in the STARMEN trial (NCT01955187), randomized to tacrolimus-rituximab (TAC-RTX) or corticosteroids-cyclophosphamide (GC-CYC), were analysed for plasma and urine cytokines using a highly sensitive chemiluminescence immunoassay providing a high-throughput multiplex analysis.

Results

Baseline (pretreatment) urinary C-X-C motif chemokine ligand 13 (CXCL13) predicted the therapeutic response to TAC-RTX. Cytokine levels evolved over the course of therapy. The levels of nine plasma and six urinary cytokines correlated with analytical parameters of kidney damage and disease activity, such as proteinuria, estimated glomerular filtration rate and circulating anti-PLA2R levels. The correlation with these parameters was most consistent for plasma and urinary growth differentiation factor 15 (GDF15), plasma tumour necrosis factor α and urinary TNF-like weak inducer of apoptosis. Decreasing plasma GDF15 levels were associated with response to GC-CYC. Four clusters of cytokines were associated with different stages of response to therapy in the full cohort, with the less inflammatory cluster associated with remission.

Conclusion

PMN displayed characteristic plasma and urine cytokine patterns that evolved over time as patients responded to therapy. Baseline urinary CXCL13 concentration could be a prognostic marker of response to TAC-RTX.

Posttransplant Tertiary Lymphoid Organs

Tertiary lymphoid organs (TLOs), also known as tertiary or ectopic lymphoid structures or tissues, are accumulations of lymphoid cells in sites other than canonical lymphoid organs, that arise through lymphoid neogenesis during chronic inflammation in autoimmunity, microbial infection, cancer, aging, and transplantation, the focus of this review. Lymph nodes and TLOs are compared regarding their cellular composition, organization, vascular components, and migratory signal regulation. These characteristics of posttransplant TLOs (PT-TLOs) are described with individual examples in a wide range of organs including heart, kidney, trachea, lung, artery, skin, leg, hand, and face, in many species including human, mouse, rat, and monkey. The requirements for induction and maintenance of TLOs include sustained exposure to autoantigens, alloantigens, tumor antigens, ischemic reperfusion, nephrotoxic agents, and aging. Several staging schemes have been put forth regarding their function in organ rejection. PT-TLOs most often are associated with organ rejection, but in some cases contribute to tolerance. The role of PT-TLOs in cancer is considered in the case of immunosuppression. Furthermore, TLOs can be associated with development of lymphomas. Challenges for PT-TLO research are considered regarding staging, imaging, and opportunities for their therapeutic manipulation to inhibit rejection and encourage tolerance.

Circulating soluble CD30 is associated with renal tertiary lymphoid structures and the progression of IgA nephropathy

BACKGROUND

Renal tertiary lymphoid structures (TLSs) are involved in renal pathology and prognosis of IgA nephropathy (IgAN). CD30 and its ligands participate in the formation of renal TLSs. However, the relationship between circulating CD30 and renal prognosis is unclear. The objective of this study was to evaluate the relationship between circulating CD30 and prognosis in patients with IgAN.

METHODS

We conducted a retrospective study including 351 patients with biopsy proved IgAN. We collected clinical and pathologic features at the time of biopsy and recorded renal follow-up outcomes. Circulating CD30 levels in IgAN patients at the time of biopsy were measured via enzyme-linked immunosorbent assay (ELISA). The association between elevated CD30 levels and the composite endpoint (defined as a ≥ 50 % decline in eGFR from baseline, end-stage renal disease, or death) was investigated using Cox regression analysis.

RESULTS

During a median follow-up period of 5.12 years, 44 (12.5 %) patients in the cohort reached the composite endpoint. Kaplan-Meier survival curve analysis revealed a significant association between higher circulating CD30 levels and a poorer renal prognosis (log-rank P < 0.001). Cox regression analysis showed that high CD30 was an independent factor for the composite endpoints in multivariable-adjusted models (HR 3.397, 95 % CI: 1.230-9.384, P = 0.018). These associations were also observed in a subgroup of patients with concomitant renal TLSs formation (10.443, 95 % CI: 1.680-65.545, P = 0.012), proteinuria > 1 g/d (HR 12.287, 95 % CI: 1.499-100.711, P = 0.019), and female patients (HR 22.372, 95 % CI: 1.797-278.520, P = 0.016).

CONCLUSION

Elevated level of circulating CD30 is an independent risk factor for renal disease progression in patients with IgAN.

Th17 cells: A new target in kidney disease research

Type 17 T helper (Th17) cells, which are a subtype of CD4+ T helper cells, secrete pro-inflammatory cytokines such as IL-17A, IL-17F, IL-21, IL-22, and GM-CSF, which play crucial roles in immune defence and protection against fungal and extracellular pathogen invasion. However, dysfunction of Th17 cell immunity mediates inflammatory responses and exacerbates tissue damage. This pathological process initiated by Th17 cells is common in kidney diseases associated with renal injury, such as glomerulonephritis, lupus nephritis, IgA nephropathy, hypertensive nephropathy, diabetic kidney disease and acute kidney injury. Therefore, targeting Th17 cells to treat kidney diseases has been a hot topic in recent years. This article reviews the mechanisms of Th17 cell-mediated inflammation and autoimmune responses in kidney diseases and discusses the related clinical drugs that modulate Th17 cell fate in kidney disease treatment.

Tertiary lymphoid structures in cancer: immune mechanisms and clinical implications

Cancer is a major cause of death globally, and traditional treatments often have limited efficacy and adverse effects. Immunotherapy has shown promise in various malignancies but is less effective in tumors with low immunogenicity or immunosuppressive microenvironment, especially sarcomas. Tertiary lymphoid structures (TLSs) have been associated with a favorable response to immunotherapy and improved survival in cancer patients. However, the immunological mechanisms and clinical significance of TLS in malignant tumors are not fully understood. In this review, we elucidate the composition, neogenesis, and immune characteristics of TLS in tumors, as well as the inflammatory response in cancer development. An in-depth discussion of the unique immune characteristics of TLSs in lung cancer, breast cancer, melanoma, and soft tissue sarcomas will be presented. Additionally, the therapeutic implications of TLS, including its role as a marker of therapeutic response and prognosis, and strategies to promote TLS formation and maturation will be explored. Overall, we aim to provide a comprehensive understanding of the role of TLS in the tumor immune microenvironment and suggest potential interventions for cancer treatment.

Tertiary lymphoid structures as local perpetuators of organ-specific immune injury: implication for lupus nephritis

In response to inflammatory stimuli in conditions such as autoimmune disorders, infections and cancers, immune cells organize in nonlymphoid tissues, which resemble secondary lymphoid organs. Such immune cell clusters are called tertiary lymphoid structures (TLS). Here, we describe the potential role of TLS in the pathogenesis of autoimmune disease, focusing on lupus nephritis, a condition that incurs major morbidity and mortality. In the kidneys of patients and animals with lupus nephritis, the presence of immune cell aggregates with similar cell composition, structure, and gene signature as lymph nodes and of lymphoid tissue-inducer and -organizer cells, along with evidence of communication between stromal and immune cells are indicative of the formation of TLS. TLS formation in kidneys affected by lupus may be instigated by local increases in lymphorganogenic chemokines such as CXCL13, and in molecules associated with leukocyte migration and vascularization. Importantly, the presence of TLS in kidneys is associated with severe tubulointerstitial inflammation, higher disease activity and chronicity indices, and poor response to treatment in patients with lupus nephritis. TLS may contribute to the pathogenesis of lupus nephritis by increasing local IFN-I production, facilitating the recruitment and supporting survival of autoreactive B cells, maintaining local production of systemic autoantibodies such as anti-dsDNA and anti-Sm/RNP autoantibodies, and initiating epitope spreading to local autoantigens. Resolution of TLS, along with improvement in lupus, by treating animals with soluble BAFF receptor, docosahexaenoic acid, complement inhibitor C4BP(β-), S1P1 receptor modulator Cenerimod, dexamethasone, and anti-CXCL13 further emphasizes a role of TLS in the pathogenesis of lupus. However, the mechanisms underlying TLS formation and their roles in the pathogenesis of lupus nephritis are not fully comprehended. Furthermore, the lack of non-invasive methods to visualize/quantify TLS in kidneys is also a major hurdle; however, recent success in visualizing TLS in lupus-prone mice by photon emission computed tomography provides hope for early detection and manipulation of TLS.

T Follicular Helper Cells in Tertiary Lymphoid Structure Contribute to Renal Fibrosis by IL-21

Tertiary lymphoid structure (TLS) represents lymphocyte clusters in non-lymphoid organs. The formation and maintenance of TLS are dependent on follicular helper T (TFH) cells. However, the role of TFH cells during renal TLS formation and the renal fibrotic process has not been comprehensively elucidated in chronic kidney disease. Here, we detected the circulating TFH cells from 57 IgAN patients and found that the frequency of TFH cells was increased in IgA nephropathy patients with renal TLS and also increased in renal tissues from the ischemic-reperfusion-injury (IRI)-induced TLS model. The inducible T-cell co-stimulator (ICOS) is one of the surface marker molecules of TFH. Remarkably, the application of an ICOS-neutralizing antibody effectively prevented the upregulation of TFH cells and expression of its canonical functional mediator IL-21, and also reduced renal TLS formation and renal fibrosis in IRI mice in vivo. In the study of this mechanism, we found that recombinant IL-21 could directly promote renal fibrosis and the expression of p65. Furthermore, BAY 11-7085, a p65 selective inhibitor, could effectively alleviate the profibrotic effect induced by IL-21 stimulation. Our results together suggested that TFH cells contribute to TLS formation and renal fibrosis by IL-21. Targeting the ICOS-signaling pathway network could reduce TFH cell infiltration and alleviate renal fibrosis.

The roles of tertiary lymphoid structures in chronic diseases

Tertiary lymphoid structures (TLSs) are ectopic lymphoid tissues that drive antigen-specific immune responses at sites of chronic inflammation. Unlike secondary lymphoid organs such as lymph nodes, TLSs lack capsules and have their own unique characteristics and functions. The presumed influence of TLSs on the disease course has led to widespread interest in obtaining a better understanding of their biology and function. Studies using single-cell analyses have suggested heterogeneity in TLS composition and phenotype, and consequently, functional correlates with disease progression are sometimes conflicting. The presence of TLSs correlates with a favourable disease course in cancer and infection. Conversely, in autoimmune diseases and chronic age-related inflammatory diseases including chronic kidney disease, the presence of TLSs is associated with a more severe disease course. However, the detailed mechanisms that underlie these clinical associations are not fully understood. To what extent the mechanisms of TLS development and maturation are shared across organs and diseases is also still obscure. Improved understanding of TLS development and function at the cellular and molecular levels may enable the exploitation of these structures to improve therapies for chronic diseases, including chronic kidney disease.

Kidney fibrosis: from mechanisms to therapeutic medicines

Chronic kidney disease (CKD) is estimated to affect 10-14% of global population. Kidney fibrosis, characterized by excessive extracellular matrix deposition leading to scarring, is a hallmark manifestation in different progressive CKD; However, at present no antifibrotic therapies against CKD exist. Kidney fibrosis is identified by tubule atrophy, interstitial chronic inflammation and fibrogenesis, glomerulosclerosis, and vascular rarefaction. Fibrotic niche, where organ fibrosis initiates, is a complex interplay between injured parenchyma (like tubular cells) and multiple non-parenchymal cell lineages (immune and mesenchymal cells) located spatially within scarring areas. Although the mechanisms of kidney fibrosis are complicated due to the kinds of cells involved, with the help of single-cell technology, many key questions have been explored, such as what kind of renal tubules are profibrotic, where myofibroblasts originate, which immune cells are involved, and how cells communicate with each other. In addition, genetics and epigenetics are deeper mechanisms that regulate kidney fibrosis. And the reversible nature of epigenetic changes including DNA methylation, RNA interference, and chromatin remodeling, gives an opportunity to stop or reverse kidney fibrosis by therapeutic strategies. More marketed (e.g., RAS blockage, SGLT2 inhibitors) have been developed to delay CKD progression in recent years. Furthermore, a better understanding of renal fibrosis is also favored to discover biomarkers of fibrotic injury. In the review, we update recent advances in the mechanism of renal fibrosis and summarize novel biomarkers and antifibrotic treatment for CKD.

The prognostic value and molecular properties of tertiary lymphoid structures in oesophageal squamous cell carcinoma

BACKGROUND

Tertiary lymphoid structures (TLSs) play key roles in tumour adaptive immunity. However, the prognostic value and molecular properties of TLSs in oesophageal squamous cell carcinoma (ESCC) patients have not been studied.

METHODS

The prognostic values of the presence and maturation status of tumour-associated TLSs were determined in 394 and 256 ESCC patients from Sun Yat-sen University Cancer Center (Centre A) and the Cancer Hospital of Shantou University Medical College (Centre B), respectively. A deep-learning (DL) TLS classifier was established with haematoxylin and eosin (H&E)-stained slides using an inception-resnet-v2 neural network. Digital spatial profiling was performed to determine the cellular and molecular properties of TLSs in ESCC tissues.

RESULTS

TLSs were observed in 73.1% of ESCCs from Centre A via pathological examination of H&E-stained primary tumour slides, among which 42.9% were TLS-mature and 30.2% were TLS-immature tumours. The established DL TLS classifier yielded favourable sensitivities and specificities for patient TLS identification and maturation evaluation, with which 55.1%, 39.5% and 5.5% of ESCCs from Centre B were identified as TLS-mature, TLS-immature and TLS-negative tumours. Multivariate analyses proved that the presence of mature TLSs was an independent prognostic factor in both the Centre A and Centre B cohorts (p < .05). Increased proportions of proliferative B, plasma and CD4+ T helper (Th) cells and increased B memory and Th17 signatures were observed in mature TLSs compared to immature ones. Intratumoural CD8+ T infiltration was increased in TLS-mature ESCC tissues compared to mature TLS-absent tissues. The combination of mature TLS presence and high CD8+ T infiltration was associated with the best survival in ESCC patients.

CONCLUSIONS

Mature TLSs improve the prognosis of ESCC patients who underwent complete resection. The use of the DL TLS classifier would facilitate precise and efficient evaluation of TLS maturation status and offer a novel probability of ESCC treatment individualization.

Tertiary Lymphatic Structures in Primary Hepatic Carcinoma: Controversy Cannot Overshadow Hope

Tertiary lymphoid structures (TLSs) are organized aggregates of immune cells found in the tumor microenvironment. TLS can influence primary hepatic carcinoma (PHC) occurrence and have an active role in cancer. TLS can promote or inhibit the growth of PHC depending on their location, and although available findings are controversial, they suggest that TLS have a protective role in PHC tissues and a non-protective role in paracancerous tissues. In addition, the cellular composition of TLS can also influence the outcome of PHC. As an immunity marker, TLS can act as a marker of immunotherapy to predict its effect and help to identify patients who will respond well to immunotherapy. Modulation of TLS formation through the use of chemokines/cytokines, immunotherapy, or induction of high endothelial vein to interfere with tumor growth has been studied extensively in PHC and other cancers. In addition, new tools such as genetic interventions, cellular crosstalk, preoperative radiotherapy, and advances in materials science have been shown to influence the prognosis of malignant tumors by modulating TLS production. These can also be used to develop PHC treatment.

Characteristics and Prognostic Value of Tertiary Lymphoid Organs in Membranous Nephropathy: A Retrospective Study

Background

Tertiary lymphoid organs play an essential role in the inflammation of the kidney. The clinical association between TLOs and membranous nephropathy (MN) is not clear yet.

Methods

Consecutive patients with the histologically confirmed membranous nephropathy in Tongji Hospital from July 19, 2012, to September 26, 2019, were included in this study. TLOs in renal biopsy tissues were detected by periodic acid–Schiff-stained and immunohistochemistry. Logistic regression was performed to evaluate the correlations of TLOs and clinical features of patients with MN. Kaplan–Meier analysis was utilized to examine the relationship between TLOs and remission of proteinuria.

Results

A total of 442 patients with MN were included in this study, of which the average age was 46.4 years old, and 58.8% were male. Moreover, 33% of patients with MN had TLOs in this study. The median value of proteinuria among patients with MN with TLOs was 4.9 g/24 h, which was much greater than no-TLOs ones (3.2 g/24 h, p < 0.001). Moreover, the patients with TLOs had higher serum creatinine and lower serum albumin. The severity of clinical features among the patients with MN aggravated with the increase in the grade of TLOs. In addition, the patients who had TLOs were more likely to be positive of anti-phospholipase A2 receptor autoantibodies. Meanwhile, the patients without TLOs showed significantly higher complete remission and total remission of proteinuria.

Conclusion

In this study, we demonstrated that TLOs were common among patients with MN. Moreover, the patients with MN with TLOs showed a worse clinical manifestation and an outcome compared with the patients without TLOs.

Identification of CCL19 as a Novel Immune-Related Biomarker in Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the major microvascular complications in diabetic patients and the leading cause of end-stage renal disease (ESRD). Previous studies found that immune-related genes and immune cell infiltration play important roles in the pathogenesis and development of DN. Therefore, this study aimed to explore immune-related biomarkers in DN. In this research, three microarray datasets that included 18 DN and 28 healthy tubule samples were downloaded and integrated as the training set to identify differentially expressed immune-related genes (DEIGs). A total of 63 DEIGs were identified, and most upregulated DEIGs were primarily involved in the inflammatory response and chemokine-mediated signaling pathways. The Microenvironment Cell Populations-counter (MCP-counter) algorithm was then used to estimate the abundance of infiltrated immune and stromal cell populations. According to DEIG, weighted gene coexpression network and protein–protein network analyses, CCL19 was identified as the hub immune-related biomarker. Moreover, the upregulated level of CCL19 was confirmed in other independent datasets as well as in in vitro experiments with high glucose. In summary, this study provides novel insights into the pathogenesis of diabetic nephropathy and identifies CCL19 as a potential critical gene of DN.

[Induction and Anti-Tumor Function of Tertiary Lymphoid Organs]

OBJECTIVE

To induce the development of tertiary lymphoid organs (TLO) in a mouse model of melanoma and to evaluate TLO's functions in antitumor immunity.

METHODS

Lymphotoxin-beta receptor (LTβR) was overexpressed in NIH3T3 cells through the lentivirus system and the overexpression efficiency of LTβR in LTβR-NIH3T3 cells was examined. Western blot and qPCR were used to examine the non-canonical nuclear factor (NF)-κB signaling pathway in NIH3T3 cells overexpressing LTβR. B16-OVA melanoma mouse model was constructed to explore the induction of TLO and anti-tumor functions of TLO in LTβR-NIH3T3 cells.

RESULTS

LTβR was overexpressed in NIH3T3 cells through the lentivirus system, and flow cytometry showed that the proportion of GFP + cells reached 99%. The overexpression of LTβR activated the non-canonical NF-κB signaling pathway in NIH3T3 cells. Findings from the mouse tumor model suggest that the injection of LTβR-NIH3T3 cells successfully induced the development of lymphoid tissue around the tumor and enhanced the tumor infiltration of T cells and MHCⅡ + macrophages, significantly inhibiting tumor growth and prolonging the survival of tumor-bearing mice.

CONCLUSION

LTβR-NIH3T3 cells promoted anti-tumor immunity by inducing TLO development, which may provide new perspectives for tumor immunotherapy.

B Cells in Primary Membranous Nephropathy: Escape from Immune Tolerance and Implications for Patient Management

Membranous nephropathy (MN) is an important cause of nephrotic syndrome and chronic kidney disease (CKD) in adults. The pathogenic significance of B cells in MN is increasingly recognized, especially following the discovery of various autoantibodies that target specific podocytic antigens and the promising treatment responses seen with B cell depleting therapies. The presence of autoreactive B cells and autoantibodies that bind to antigens on podocyte surfaces are characteristic features of MN, and are the result of breaches in central and peripheral tolerance of B lymphocytes. These perturbations in B cell tolerance include altered B lymphocyte subsets, dysregulation of genes that govern immunoglobulin production, aberrant somatic hypermutation and co-stimulatory signalling, abnormal expression of B cell-related cytokines, and increased B cell infiltrates and organized tertiary lymphoid structures within the kidneys. An understanding of the role of B cell tolerance and homeostasis may have important implications for patient management in MN, as conventional immunosuppressive treatments and novel B cell-targeted therapies show distinct effects on proliferation, differentiation and reconstitution in different B cell subsets. Circulating B lymphocytes and related cytokines may serve as potential biomarkers for treatment selection, monitoring of therapeutic response and prediction of disease relapse. These recent advances in the understanding of B cell tolerance in MN have provided greater insight into its immunopathogenesis and potential novel strategies for disease monitoring and treatment.

The Th17/IL-17 Axis and Kidney Diseases, With Focus on Lupus Nephritis

Systemic lupus erythematosus (SLE) is a disease characterized by dysregulation and hyperreactivity of the immune response at various levels, including hyperactivation of effector cell subtypes, autoantibodies production, immune complex formation, and deposition in tissues. The consequences of hyperreactivity to the self are systemic and local inflammation and tissue damage in multiple organs. Lupus nephritis (LN) is one of the most worrying manifestations of SLE, and most patients have this involvement at some point in the course of the disease. Among the effector cells involved, the Th17, a subtype of T helper cells (CD4+), has shown significant hyperactivation and participates in kidney damage and many other organs. Th17 cells have IL-17A and IL-17F as main cytokines with receptors expressed in most renal cells, being involved in the activation of many proinflammatory and profibrotic pathways. The Th17/IL-17 axis promotes and maintains repetitive tissue damage and maladaptive repair; leading to fibrosis, loss of organ architecture and function. In the podocytes, the Th17/IL-17 axis effects include changes of the cytoskeleton with increased motility, decreased expression of health proteins, increased oxidative stress, and activation of the inflammasome and caspases resulting in podocytes apoptosis. In renal tubular epithelial cells, the Th17/IL-17 axis promotes the activation of profibrotic pathways such as increased TGF-β expression and epithelial-mesenchymal transition (EMT) with consequent increase of extracellular matrix proteins. In addition, the IL-17 promotes a proinflammatory environment by stimulating the synthesis of inflammatory cytokines by intrinsic renal cells and immune cells, and the synthesis of growth factors and chemokines, which together result in granulopoiesis/myelopoiesis, and further recruitment of immune cells to the kidney. The purpose of this work is to present the prognostic and immunopathologic role of the Th17/IL-17 axis in Kidney diseases, with a special focus on LN, including its exploration as a potential immunotherapeutic target in this complication.

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

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

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

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