Interactions of T cells with fibroblast-like synoviocytes: role of the B7 family costimulatory ligand B7-H3

HLA-DR-Expressing Fibroblast-Like Synoviocytes Are Inducible Antigen Presenting Cells That Present Autoantigens in Lyme Arthritis

OBJECTIVE

HLA-DR-expressing fibroblast-like synoviocytes (FLS) are a prominent cell type in synovial tissue in chronic inflammatory forms of arthritis. FLS-derived extracellular matrix (ECM) proteins, including fibronectin-1 (FN1), contain immunogenic CD4+ T cell epitopes in patients with postinfectious Lyme arthritis (LA). However, the role of FLS in presentation of these T cell epitopes remains uncertain.

METHODS

Primary LA FLS and primary murine FLS stimulated with interferon gamma (IFNγ), Borrelia burgdorferi, and/or B burgdorferi peptidoglycan (PG) were assessed for properties associated with antigen presentation. HLA-DR-presented peptides from stimulated LA FLS were identified by immunopeptidomics analysis. OT-II T cells were co-cultured with stimulated murine FLS in the presence of cognate ovalbumin antigen to determine the potential of FLS to act as inducible antigen presenting cells (APCs).

RESULTS

FLS expressed HLA-DR molecules within inflamed synovial tissue and tendons from patients with postinfectious LA in situ. Major histocompatibility complex (MHC) class II and co-stimulatory molecules were expressed by FLS following in vitro stimulation with IFNγ and B burgdorferi and presented both foreign and self-MHC-II peptides, including an immunogenic T cell epitope derived from Lyme autoantigen FN1. Stimulated FLS induced proliferation of naive OT-II CD4+ T cells that were dependent on OT-II antigen and CD40. Stimulation with B burgdorferi PG enhanced FLS-mediated T cell activation.

CONCLUSION

MHC-II+ FLS are inducible APCs that can induce CD4+ T cell activation in an antigen- and CD40-dependent manner. Activated FLS can also present ECM-derived Lyme autoantigens, implicating FLS in amplifying tissue-localized autoimmunity in LA.

Neointimal myofibroblasts contribute to maintaining Th1/Tc1 and Th17/Tc17 inflammation in giant cell arteritis

Vascular smooth muscle cells (VSMCs) have been shown to play a role in the pathogenesis of giant cell arteritis (GCA) through their capacity to produce chemokines recruiting T cells and monocytes in the arterial wall and their ability to migrate and proliferate in the neointima where they acquire a myofibroblast (MF) phenotype, leading to vascular stenosis. This study aimed to investigate if MFs could also impact T-cell polarization. Confocal microscopy was used to analyze fresh fragments of temporal artery biopsies (TABs). Healthy TAB sections were cultured to obtain MFs, which were then treated or not with interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) and analyzed by immunofluorescence and RT-PCR. After peripheral blood mononuclear cells and MFs were co-cultured for seven days, T-cell polarization was analyzed by flow cytometry. In the neointima of GCA arteries, we observed a phenotypic heterogeneity among VSMCs that was consistent with a MF phenotype (α-SMA+CD90+desmin+MYH11+) with a high level of STAT1 phosphorylation. Co-culture experiments showed that MFs sustain Th1/Tc1 and Th17/Tc17 polarizations. The increased Th1 and Tc1 polarization was further enhanced following the stimulation of MFs with IFN-γ and TNF-α, which induced STAT1 phosphorylation in MFs. These findings correlated with increases in the production of IL-1β, IL-6, IL-12 and IL-23 by MFs. Our study showed that MFs play an additional role in the pathogenesis of GCA through their ability to maintain Th17/Tc17 and Th1/Tc1 polarizations, the latter being further enhanced in case of stimulation of MF with IFN-γ and TNF-α.

Targeting glycolytic pathway in fibroblast-like synoviocytes for rheumatoid arthritis therapy: challenges and opportunities

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by hyperplastic synovium, pannus formation, immune cell infiltration, and potential articular cartilage damage. Notably, fibroblast-like synoviocytes (FLS), especially rheumatoid arthritis fibroblast-like synoviocytes (RAFLS), exhibit specific overexpression of glycolytic enzymes, resulting in heightened glycolysis. This elevated glycolysis serves to generate ATP and plays a pivotal role in immune regulation, angiogenesis, and adaptation to hypoxia. Key glycolytic enzymes, such as hexokinase 2 (HK2), phosphofructose-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), and pyruvate kinase M2 (PKM2), significantly contribute to the pathogenic behavior of RAFLS. This increased glycolysis activity is regulated by various signaling pathways.

MATERIALS AND METHODS

A comprehensive literature search was conducted to retrieve relevant studies published from January 1, 2010, to the present, focusing on RAFLS glycolysis, RA pathogenesis, glycolytic regulation pathways, and small-molecule drugs targeting glycolysis.

CONCLUSION

This review provides a thorough exploration of the pathological and physiological characteristics of three crucial glycolytic enzymes in RA. It delves into their putative regulatory mechanisms, shedding light on their significance in RAFLS. Furthermore, the review offers an up-to-date overview of emerging small-molecule candidate drugs designed to target these glycolytic enzymes and the upstream signaling pathways that regulate them. By enhancing our understanding of the pathogenic mechanisms of RA and highlighting the pivotal role of glycolytic enzymes, this study contributes to the development of innovative anti-rheumatic therapies.

Human leukocyte antigen HLA-DR-expressing fibroblast-like synoviocytes are inducible antigen presenting cells that present autoantigens in Lyme arthritis

Background

HLA-DR-expressing fibroblast-like synoviocytes (FLS) are a prominent cell type in synovial tissue in chronic inflammatory forms of arthritis. We recently showed that peptides from several extracellular matrix (ECM) proteins, including fibronectin-1 (FN1), contained immunogenic CD4+ T cell epitopes in patients with postinfectious Lyme arthritis (LA). However, the role of FLS in presentation of these T cell epitopes remains uncertain.

Methods

Primary LA FLS and primary murine FLS stimulated with interferon gamma (IFNγ), Borrelia burgdorferi, and/or B. burgdorferi peptidoglycan (PG) were assessed for properties associated with antigen presentation. HLA-DR-presented peptides from stimulated LA FLS were identified by immunopeptidomics analysis. OT-II T cells were cocultured with stimulated murine FLS in the presence of cognate ovalbumin antigen to determine the potential of FLS to act as inducible antigen presenting cells (APC).

Results

FLS expressed HLA-DR molecules within inflamed synovial tissue and tendons from patients with post-infectious LA patients in situ. MHC class II and costimulatory molecules were expressed by FLS following in vitro stimulation with IFNγ and B. burgdorferi and presented both foreign and self MHC-II peptides, including T cell epitopes derived from two Lyme autoantigens fibronectin-1 (FN1) and endothelial cell growth factor (ECGF). Stimulated murine FLS induced proliferation of naïve OT-II CD4+ T cells, particularly when FLS were stimulated with both IFNγ and PG.

Conclusions

MHC-II+ FLS are inducible APCs that can induce CD4+ T cell activation and can present Lyme autoantigens derived from ECM proteins, thereby amplifying tissue-localized autoimmune CD4+ T cell responses in LA.

Cytokine-directed cellular cross-talk imprints synovial pathotypes in rheumatoid arthritis

INTRODUCTION

Structural reorganisation of the synovium with expansion of fibroblast-like synoviocytes (FLS) and influx of immune cells is a hallmark of rheumatoid arthritis (RA). Activated FLS are increasingly recognised as a critical component driving synovial tissue remodelling by interacting with immune cells resulting in distinct synovial pathotypes of RA.

METHODS

Automated high-content fluorescence microscopy of co-cultured cytokine-activated FLS and autologous peripheral CD4+ T cells from patients with RA was established to quantify cell-cell interactions. Phenotypic profiling of cytokine-treated FLS and co-cultured T cells was done by flow cytometry and RNA-Seq, which were integrated with publicly available transcriptomic data from patients with different histological synovial pathotypes. Computational prediction and knock-down experiments were performed in FLS to identify adhesion molecules for cell-cell interaction.

RESULTS

Cytokine stimulation, especially with TNF-α, led to enhanced FLS-T cell interaction resulting in cell-cell contact-dependent activation, proliferation and differentiation of T cells. Signatures of cytokine-activated FLS were significantly enriched in RA synovial tissues defined as lymphoid-rich or leucocyte-rich pathotypes, with the most prominent effects for TNF-α. FLS cytokine signatures correlated with the number of infiltrating CD4+ T cells in synovial tissue of patients with RA. Ligand-receptor pair interaction analysis identified ICAM1 on FLS as an important mediator in TNF-mediated FLS-T cell interaction. Both, ICAM1 and its receptors were overexpressed in TNF-treated FLS and co-cultured T cells. Knock-down of ICAM1 in FLS resulted in reduced TNF-mediated FLS-T cell interaction.

CONCLUSION

Our study highlights the role of cytokine-activated FLS in orchestrating inflammation-associated synovial pathotypes providing novel insights into disease mechanisms of RA.

Advances of the small molecule drugs regulating fibroblast-like synovial proliferation for rheumatoid arthritis

Rheumatoid arthritis (RA) is a type of chronic autoimmune and inflammatory disease. In the pathological process of RA, the alteration of fibroblast-like synoviocyte (FLS) and its related factors is the main influence in the clinic and fundamental research. In RA, FLS exhibits a uniquely aggressive phenotype, leading to synovial hyperplasia, destruction of the cartilage and bone, and a pro-inflammatory environment in the synovial tissue for perpetuation and progression. Evidently, it is a highly promising way to target the pathological function of FLS for new anti-RA drugs. Based on this, we summed up the pathological mechanism of RA-FLS and reviewed the recent progress of small molecule drugs, including the synthetic small molecule compounds and natural products targeting RA-FLS. In the end, there were some views for further action. Compared with MAPK and NF-κB signaling pathways, the JAK/STAT signaling pathway has great potential for research as targets. A small number of synthetic small molecule compounds have entered the clinic to treat RA and are often used in combination with other drugs. Meanwhile, most natural products are currently in the experimental stage, not the clinical trial stage, such as triptolide. There is an urgent need to unremittingly develop new agents for RA.

New frontiers in immune checkpoint B7-H3 (CD276) research and drug development

B7-H3 (CD276), a member of the B7 family of proteins, is a key player in cancer progression. This immune checkpoint molecule is selectively expressed in both tumor cells and immune cells within the tumor microenvironment. In addition to its immune checkpoint function, B7-H3 has been linked to tumor cell proliferation, metastasis, and therapeutic resistance. Furthermore, its drastic difference in protein expression levels between normal and tumor tissues suggests that targeting B7-H3 with drugs would lead to cancer-specific toxicity, minimizing harm to healthy cells. These properties make B7-H3 a promising target for cancer therapy.Recently, important advances in B7-H3 research and drug development have been reported, and these new findings, including its involvement in cellular metabolic reprograming, cancer stem cell enrichment, senescence and obesity, have expanded our knowledge and understanding of this molecule, which is important in guiding future strategies for targeting B7-H3. In this review, we briefly discuss the biology and function of B7-H3 in cancer development. We emphasize more on the latest findings and their underlying mechanisms to reflect the new advances in B7-H3 research. In addition, we discuss the new improvements of B-H3 inhibitors in cancer drug development.

Two Main Cellular Components in Rheumatoid Arthritis: Communication Between T Cells and Fibroblast-Like Synoviocytes in the Joint Synovium

Rheumatoid arthritis (RA) is a chronic autoimmune disease that endangers the health of approximately 1% of the global population. Current RA medications on the market mainly include non-steroidal anti-inflammatory drugs, biological agents, and disease-modifying drugs. These drugs aim to inhibit the overactivated immune response or inflammation of RA, but they cannot cure RA. A better understanding of the pathogenesis of RA will provide a new understanding to search for RA targets and for drug development. The infiltration of T cells and hyper-proliferation of fibroblast-like synoviocytes (FLS) in the synovium of patients with RA are significantly upregulated. Furthermore, the abnormal activation of these two types of cells has been confirmed to promote development of the course of A by many studies. This article systematically summarizes the interactions between T cells and FLS in RA synovial tissues, including one-way/mutual regulation and direct/indirect regulation between the two. It further aims to investigate the pathogenesis of RA from the perspective of mutual regulation between T cells and FLS and to provide new insights into RA research.

Immunomodulatory Properties of Immune Checkpoint Inhibitors-More than Boosting T-Cell Responses?

The approval of immune checkpoint inhibitors (ICI) that serve to enhance effector T-cell anti-tumor responses has strongly improved success rates in the treatment of metastatic melanoma and other tumor types. The currently approved ICI constitute monoclonal antibodies blocking cytotoxic T-lymphocyte-associated protein (CTLA)-4 and anti-programmed cell death (PD)-1. By this, the T-cell-inhibitory CTLA-4/CD80/86 and PD-1/PD-1L/2L signaling axes are inhibited. This leads to sustained effector T-cell activity and circumvents the immune evasion of tumor cells, which frequently upregulate PD-L1 expression and modulate immune checkpoint molecule expression on leukocytes. As a result, profound clinical responses are observed in 40-60% of metastatic melanoma patients. Despite the pivotal role of T effector cells for triggering anti-tumor immunity, mounting evidence indicates that ICI efficacy may also be attributable to other cell types than T effector cells. In particular, emerging research has shown that ICI also impacts innate immune cells, such as myeloid cells, natural killer cells and innate lymphoid cells, which may amplify tumoricidal functions beyond triggering T effector cells, and thus improves clinical efficacy. Effects of ICI on non-T cells may additionally explain, in part, the character and extent of adverse effects associated with treatment. Deeper knowledge of these effects is required to further develop ICI treatment in terms of responsiveness of patients to treatment, to overcome resistance to ICI and to alleviate adverse effects. In this review we give an overview into the currently known immunomodulatory effects of ICI treatment in immune cell types other than the T cell compartment.

[Preliminary study on the effect of B7H3 interaction with fibronectin on apoptosis of human chronic myeloid leukemia cells]

Objective: To explore the effect of the interaction between B7H3 and fibronectin (FN) on the apoptosis of human chronic myeloid leukemia K562 cells. Methods: The expression of B7H3 molecules in K562 cells was detected using flow cytometry and B7H3 overexpressing cells were constructed. The interaction between B7H3 and FN was detected using the co-immunoprecipitation technology. After adding exogenous FN, cell experiments were performed to detect changes in adhesion and cell apoptosis. The changes in apoptosis-related proteins and PI3K/AKT signaling pathway were detected using Western blot. Results: The expression of B7H3 was low in K562, and the cell line K562 OE (overexpression) -B7H3 and the control cell line K562 NC (negative control) -B7H3 were obtained after lentivirus transfection. There is an interaction between B7H3 and FN (P=0.036) , and this interaction promoted cell adhesion (P<0.05) , inhibited cell apoptosis (P<0.05) , and activated the PI3K/AKT signaling pathway (P<0.05) . Conclusion: B7H3 interacts with FN to promote cell adhesion and may inhibit K562 cell apoptosis by activating the PI3K/AKT signaling pathway.

B7-H3 regulates osteoclast differentiation via type I interferon-dependent IDO induction

While their function, as immune checkpoint molecules, is well known, B7-family proteins also function as regulatory molecules in bone remodeling. B7-H3 is a receptor ligand of the B7 family that functions primarily as a negative immune checkpoint. While the regulatory function of B7-H3 in osteoblast differentiation has been established, its role in osteoclast differentiation remains unclear. Here we show that B7-H3 is highly expressed in mature osteoclasts and that B7-H3 deficiency leads to the inhibition of osteoclastogenesis in human osteoclast precursors (OCPs). High-throughput transcriptomic analyses reveal that B7-H3 inhibition upregulates IFN signaling as well as IFN-inducible genes, including IDO. Pharmacological inhibition of type-I IFN and IDO knockdown leads to reversal of B7-H3-deficiency-mediated osteoclastogenesis suppression. Although synovial-fluid macrophages from rheumatoid-arthritis patients express B7-H3, inhibition of B7-H3 does not affect their osteoclastogenesis. Thus, our findings highlight B7-H3 as a physiologic positive regulator of osteoclast differentiation and implicate type-I IFN-IDO signaling as its downstream mechanism.

CD276 is an important player in macrophage recruitment into the tumor and an upstream regulator for PAI-1

More than 70% of colorectal, prostate, ovarian, pancreatic and breast cancer specimens show expression of CD276 (B7–H3), a potential immune checkpoint family member. Several studies have shown that high CD276 expression in cancer cells correlates with a poor clinical prognosis. This has been associated with the presence of lower tumor infiltrating leukocytes. Among those, tumor-associated macrophages can comprise up to 50% of the tumor mass and are thought to support tumor growth through various mechanisms. However, a lack of information on CD276 function and interaction partner(s) impedes rigorous evaluation of CD276 as a therapeutic target in oncology. Therefore, we aimed to understand the relevance of CD276 in tumor-macrophage interaction by employing a 3D spheroid coculture system with human cells. Our data show a role for tumor-expressed CD276 on the macrophage recruitment into the tumor spheroid, and also in regulation of the extracellular matrix modulator PAI-1. Furthermore, our experiments focusing on macrophage-expressed CD276 suggest that the antibody-dependent CD276 engagement triggers predominantly inhibitory signaling networks in human macrophages.

High TIL, HLA, and Immune Checkpoint Expression in Conventional High-Grade and Dedifferentiated Chondrosarcoma and Poor Clinical Course of the Disease

Purpose

The aim of this study was to characterize chondrosarcoma tumor infiltration by immune cells and the expression of immunologically relevant molecules. This information may contribute to our understanding of the role of immunological events in the pathogenesis of chondrosarcoma and to the rational design of immunotherapeutic strategies.

Patients and Methods

A tissue microarray (TMA) containing 52 conventional and 24 dedifferentiated chondrosarcoma specimens was analyzed by immunohistochemical staining for the expression of parameters associated with tumor antigen-specific immune responses, namely, CD4⁺ and CD8⁺ tumor infiltrating lymphocytes (TILs) and the expression of HLA class I heavy chain, beta-2 microglobulin (β2m), HLA class II and immune checkpoint molecules, B7-H3 and PD-1/PD-L1. The results were correlated with histopathological characteristics and the clinical course of the disease.

Results

CD8⁺ TILs were present in 21% of the conventional and 90% of the dedifferentiated chondrosarcoma tumors tested. B7-H3 was expressed in 69% of the conventional and 96% of the dedifferentiated chondrosarcoma tumors tested. PD-1 and PD-L1 were expressed 53% and 33% respectively of the dedifferentiated tumors tested. PD-L1 expression was associated with shorter time to metastasis.

Conclusion

The tumor infiltration by lymphocytes suggests that chondrosarcoma is immunogenic. Defects in HLA class I antigen and expression of the checkpoint molecules B7-H3 and PD-1/PD-L1 suggest that tumor cells utilize escape mechanisms to avoid immune recognition and destruction. This data implies that chondrosarcoma will benefit from strategies that enhance the immunogenicity of tumor antigens and/or counteract the escape mechanisms.

Transformation of fibroblast-like synoviocytes in rheumatoid arthritis; from a friend to foe

Swelling and the progressive destruction of articular cartilage are major characteristics of rheumatoid arthritis (RA), a systemic autoimmune disease that directly affects the synovial joints and often causes severe disability in the affected positions. Recent studies have shown that type B synoviocytes, which are also called fibroblast-like synoviocytes (FLSs), as the most commonly and chiefly resident cells, play a crucial role in early-onset and disease progression by producing various mediators. During the pathogenesis of RA, the FLSs' phenotype is altered, and represent invasive behavior similar to that observed in tumor conditions. Modified and stressful microenvironment by FLSs leads to the recruitment of other immune cells and, eventually, pannus formation. The origins of this cancerous phenotype stem fundamentally from the significant metabolic changes in glucose, lipids, and oxygen metabolism pathways. Moreover, the genetic abnormalities and epigenetic alterations have recently been implicated in cancer-like behaviors of RA FLSs. In this review, we will focus on the mechanisms underlying the transformation of FLSs to a cancer-like phenotype during RA. A comprehensive understanding of these mechanisms may lead to devising more effective and targeted treatment strategies.

Anti-citrullinated protein antibodies are associated with neutrophil extracellular trap formation in rheumatoid arthritis

Objectives

We evaluated the associations of anti‐citrullinated protein antibodies (ACPAs) and serological and cytological levels of neutrophil extracellular trap (NET) formation in rheumatoid arthritis (RA) patients.

Methods

Serum levels of myeloperoxidase‐DNA and elastase‐DNA complexes (NET remnants) were examined in 51 patients with RA and 40 healthy controls using a modified enzyme‐linked immunosorbent assay. Neutrophils were isolated by density gradient centrifugation. IgG antibodies were purified by affinity chromatography. NET formation in RA and control neutrophils was assessed by microscopy in vitro. NETs were purified and co‐incubated with fibroblast‐like synoviocyte (FLS) cells. Interleukin (IL)‐6 and IL‐8 mRNA expression and protein levels in FLS cells were determined by real‐time polymerase chain reaction and enzyme‐linked immunosorbent assay, respectively.

Results

In RA patients, NET remnants in the peripheral circulation were higher in extremely high ACPA titers when compared to in moderate ACPA titers. And IgG antibodies containing ACPA can stimulate neutrophils to form NETs in a concentration‐dependent manner. Furthermore, significantly higher expression of the pro‐inflammatory cytokines IL‐6 and IL‐8 is detected after FLS cells interacted with NETs which derived from neutrophils stimulated with ACPA‐containing IgG antibodies.

Conclusions

Anti‐citrullinated protein antibodies may enhance NET formation and contribute to inflammation development in RA by stimulating NET formation, such as by subsequent activation of FLS cells by NETs.

B7-H3 Immune Checkpoint Protein in Human Cancer

B7-H3 belongs to the B7 family of immune checkpoint proteins, which are important regulators of the adaptive immune response and emerging key players in human cancer. B7-H3 is a transmembrane protein expressed on the surface of tumor cells, antigen presenting cells, natural killer cells, tumor endothelial cells, but can also be present in intra- and extracellular vesicles. Additionally, B7-H3 may be present as a circulating soluble isoform in serum and other body fluids. B7-H3 is overexpressed in a variety of tumor types, in correlation with poor prognosis. B7-H3 is a promising new immunotherapy target for anti-cancer immune response, as well as a potential biomarker. Besides its immunoregulatory role, B7-H3 has intrinsic pro-tumorigenic activities related to enhanced cell proliferation, migration, invasion, angiogenesis, metastatic capacity and anti-cancer drug resistance. B7-H3 has also been found to regulate key metabolic enzymes, promoting the high glycolytic capacity of cancer cells. B7-H3 receptors are still not identified, and little is known about the molecular mechanisms underlying B7-H3 functions. Here, we review the current knowledge on the involvement of B7-H3 in human cancer.

News on immune checkpoint inhibitors as immunotherapy strategies in adult and pediatric solid tumors

Immune checkpoint inhibitors (ICIs) have shown unprecedented benefits in various adult cancers, and this success has prompted the exploration of ICI therapy even in childhood malignances. Although the use of ICIs as individual agents has achieved disappointing response rates, combinational therapies are likely to promise better results. However, only a subset of patients experienced prolonged clinical effects, thus suggesting the need to identify robust bio-markers that predict individual clinical response or resistance to ICI therapy as the main challenge. In this review, we focus on how the use of ICIs in adult cancers can be translated into pediatric malignances. We discuss the physiological mechanism of action of each IC, including PD-1, PD-L1 and CTLA-4 and the new emerging ones, LAG-3, TIM-3, TIGIT, B7-H3, BTLA and IDO-1, and evaluate their prognostic value in both adult and childhood tumors. Furthermore, we offer an overview of preclinical models and clinical trials currently under investigation to improve the effectiveness of cancer immunotherapies in these patients. Finally, we outline the main predictive factors that influence the efficacy of ICIs, in order to lay the basis for the development of a pan-cancer immunogenomic model, able to direct young patients towards more specific immunotherapy.

New insights into IFN-γ in rheumatoid arthritis: role in the era of JAK inhibitors

The treatment of rheumatoid arthritis (RA) is now entering a new era, the era of Janus kinase (JAK) inhibitors. JAK inhibitors target multiple cytokines including IL-6 and exhibit a beneficial treatment effect in patients with RA and inadequate response to conventional synthetic or biologic disease-modifying anti-rheumatic drugs. Since the treatment effect of JAK inhibitors is promising even for patients refractory to anti-IL-6 therapy, it needs to be considered how multiple cytokines play roles in the pathogenesis of RA. It is also worth noting that an increased risk of herpes zoster is specifically related to the use of JAK inhibitors. Among cytokines targeted by JAK inhibitors, the current review focuses on IFN-γ, particularly on its role in synovial biology, autoimmunity, bone metabolism, pain, and varicella zoster virus infection. Recent studies provided new insights into IFN-γ in the pathogenesis of RA, which may account for the efficacy of JAK inhibitors.

B7-H3: A promising therapeutic target for autoimmune diseases

B7-H3 as a newly identified costimulatory molecule that belongs to B7 ligand family, is broadly expressed in both lymphoid and non-lymphoid tissues. The overexpression of B7-H3 has been verified to be correlated with the poor prognosis and poor clinical outcome of several human cancers. In recent years, researchers reveal that B7-H3 is involved in the pathogenesis of various autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), Sjögren's syndrome (SS), ankylosing spondylitis (AS), etc. In this review, we will discuss the biological function of B7-H3 and summarize the progress made over past years regarding its role in the occurrence and development of autoimmune diseases. The insights gained from these findings could serve as the foundation for future therapies of these diseases.

B7-H3 modulates endothelial cell angiogenesis through the VEGF cytokine

B7-H3 is a cell surface molecule in the immunoglobulin superfamily that has been shown to perform both immunological and non-immunological functions. It has also been found that vascular endothelial growth factor (VEGF) is an important molecule in the modulation of endothelial cell behavior. In this study, we analyzed the serum expression of B7-H3 in 113 rheumatoid arthritis and systemic lupus erythematous patients using the ELISA and found a positive correlation between B7-H3 and VEGF. Next, we investigated the involvement of B7-H3 in angiogenesis using human umbilical vein endothelial cells (HUVECs) with transient knockdown of B7-H3 and an in vivo Matrigel model. Data from the in vitro experiments showed that B7-H3 increased cell proliferation, migration, and tube formation, and correlated with the expression of VEGF. Furthermore, B7-H3 affected the formation of functional vascular networks in Matrigel plugs, which were dissected from mice injected with different HUVECs. Our data suggest that B7-H3 promotes angiogenesis through the enhancement of VEGF secretion. This is the first study proposing a significant role for B7-H3 in the promotion of angiogenesis and may provide further understanding of this gene's biological function.

Overexpression of B7-H3 in α-SMA-Positive Fibroblasts Is Associated With Cancer Progression and Survival in Gastric Adenocarcinomas

Background: B7-H3 promotes tumor immune escape and is highly expressed in tumor tissues. Stromal cells in tumors, including fibroblasts, play an important role in this process; however, the role of B7-H3 in tumor fibroblasts has not been fully clarified.

Methods: We examined B7-H3, CD31, and alpha-smooth muscle actin (α-SMA) protein expression in 268 gastric adenocarcinomas (GACs) by immunohistochemistry. The coexpression of B7-H3 with CD31 or α-SMA was examined using immunofluorescence double staining. Cytokine expression from fibroblasts treated with B7-H3 small interfering RNA (siRNA) was analyzed by a Quantitative reverse transcription-polymerase chain reaction (qPCR) and Enzyme-linked immunosorbent assay (ELISA). The transwell tests were conducted to assess the migration and invasion ability of fibroblasts. The overall survival was analyzed by a Kaplan-Meier analysis. Associations between categorical variables were assessed using the Pearson's Chi-square test or Fisher's exact test.

Results: GAC patients with B7-H3 expression showed significantly poorer survival (P = 0.012). The overall survival of the group with high B7-H3 expression was significantly worse than the group with low B7-H3 expression in both tumor cells and in stromal cells (P = 0.007 and P = 0.048, respectively). B7-H3 expression correlated with many clinicopathological data, including tumor stage, tumor depth, lymph node involvement, and survival. Immunofluorescence staining showed that B7-H3 was expressed in tumor cells and α-SMA-positive fibroblasts. Remarkably, high expression of α-SMA was associated with a poor prognosis (P = 0.007), and the prognoses of patients with high stromal expression of B7-H3 and α-SMA were significantly worse than that of other combination types (P = 0.001). Additionally, the absence of B7-H3 led to decreased secretion of cytokines, such as interleukin (IL)-6 and vascular endothelial growth factor (VEGF), as well as a decline in migration and invasion ability in cancer-associated fibroblasts (CAFs).

Conclusions: Patients with high B7-H3 expression either in tumor cells or in stromal cells had significantly poorer overall survival. Stromal B7-H3 expression was mostly detected in α-SMA-positive CAFs. GAC patients with both stromal B7-H3-high and α-SMA-high expression had significantly poorer overall survival, suggesting that stromal B7-H3 and α-SMA expression status can serve as an indicator of poor prognosis for GAC patients.

Autophagy promotes citrullination of VIM (vimentin) and its interaction with major histocompatibility complex class II in synovial fibroblasts

We aimed to investigate the involvement of macroautophagy/autophagy in autoimmunity in rheumatoid arthritis (RA) through citrullination of VIM (vimentin) and its interaction with MHC class II in synovial fibroblasts (SFs). The cell surface expression of MHC class II and B7 costimulatory molecules on SFs was analyzed by flow cytometry after treatment with IFNG/IFN-γ (interferon gamma). Intracellular citrullinated autoantigens in SFs were analyzed by immunoblotting using serum from anti-citrullinated peptide antibodies (ACPA)-positive patient as a primary antibody. SFs were incubated in serum-free medium or treated with proteasome inhibitor MG132 to induce autophagy. An autophagy inhibitor 3-methyladenin (3-MA) was used. Intracellular citrullinated VIM (cVIM) was evaluated by immunoblotting and immunocytochemistry. The interaction between MHC class II and cVIM was evaluated with co-immunoprecipitation and proximity ligation assay (PLA). We demonstrated that MHC class II, CD274/B7-H1 and PDCD1LG2/B7-DC were expressed on SFs following treatment with IFNG whereas CD276/B7-H3 was detected on SFs regardless of the presence of IFNG. ACPA-positive sera recognized a 54 kDa protein in SFs. By immunoprecipitation, the 54 kDa protein recognized by RA sera was revealed to be cVIM. Following induction of autophagy, intracellular cVIM was increased in SFs but the effect was canceled by 3-MA. The interaction between MHC class II and cVIM was demonstrated by co-immunoprecipitation. Furthermore, PLA revealed the significant increase of MHC class II-cVIM interaction following induction of autophagy. Our findings suggest that SFs may contribute to the autoimmunity in RA through citrullination of VIM and its interaction with MHC class II promoted by autophagy.Abbreviations: 3-MA: 3-methyladenine; ACPA: anti-citrullinated peptide antibodies; anti-CCP: anti-cyclic citrullinated peptide antibody; cVIM: citrullinated VIM; BECN1: beclin1; DAPI: 4',6-diamidino-2-phenylindole; FBS: fetal bovine serum; HLA: human leukocyte antigen; IFNG/IFN-γ: interferon gamma; IL6: interleukin 6; IP: immunoprecipitation; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFI: mean fluorescence index; MHC: major histocompatibility complex; OA: osteoarthritis; PADI: peptidyl arginine deiminase; PepA: pepstatin A; PBS: phosphate-buffered saline; PtdIns3K: phosphatidylinositol 3-kinase; RA: rheumatoid arthritis; SFs: synovial fibroblasts; siRNA: small interfering RNA; VIM: vimentin.

KCa1.1 and Kv1.3 channels regulate the interactions between fibroblast-like synoviocytes and T lymphocytes during rheumatoid arthritis

BACKGROUND

Fibroblast-like synoviocytes (FLS) and CCR7- effector memory T (TEM) cells are two of the major cell types implicated in the progression of rheumatoid arthritis (RA). In particular, FLS become highly invasive, whereas TEM cells proliferate and secrete proinflammatory cytokines, during RA. FLS and T cells may also interact and influence each other's phenotypes. Inhibition of the pathogenic phenotypes of both FLS and TEM cells can be accomplished by selectively blocking the predominant potassium channels that they upregulate during RA: KCa1.1 (BK, Slo1, MaxiK, KCNMA1) upregulated by FLS and Kv1.3 (KCNA3) upregulated by activated TEM cells. In this study, we investigated the roles of KCa1.1 and Kv1.3 in regulating the interactions between FLS and TEM cells and determined if combination therapies of KCa1.1- and Kv1.3-selective blockers are more efficacious than monotherapies in ameliorating disease in rat models of RA.

METHODS

We used in vitro functional assays to assess the effects of selective KCa1.1 and Kv1.3 channel inhibitors on the interactions of FLS isolated from rats with collagen-induced arthritis (CIA) with syngeneic TEM cells. We also used flow cytometric analyses to determine the effects of KCa1.1 blockers on the expression of proteins used for antigen presentation on CIA-FLS. Finally, we used the CIA and pristane-induced arthritis models to determine the efficacy of combinatorial therapies of KCa1.1 and Kv1.3 blockers in reducing disease severity compared with monotherapies.

RESULTS

We show that the interactions of FLS from rats with CIA and of rat TEM cells are regulated by KCa1.1 and Kv1.3. Inhibiting KCa1.1 on FLS reduces the ability of FLS to stimulate TEM cell proliferation and migration, and inhibiting Kv1.3 on TEM cells reduces TEM cells' ability to enhance FLS expression of KCa1.1 and major histocompatibility complex class II protein, as well as stimulates their invasion. Furthermore, we show that combination therapies of selective KCa1.1 and Kv1.3 blockers are more efficacious than monotherapies at reducing signs of disease in two rat models of RA.

CONCLUSIONS

Our results demonstrate the importance of KCa1.1 and Kv1.3 in regulating FLS and TEM cells during RA, as well as the value of combined therapies targeting both of these cell types to treat RA.

Interferon-gamma production in Lyme arthritis synovial tissue promotes differentiation of fibroblast-like synoviocytes into immune effector cells

Lyme arthritis (LA), a late disease manifestation of Borrelia burgdorferi infection, usually resolves with antibiotic therapy. However, some patients develop proliferative synovitis lasting months to several years after spirochetal killing, called postinfectious LA. In this study, we phenotyped haematopoietic and stromal cell populations in the synovial lesion ex vivo and used these findings to generate an in vitro model of LA using patient-derived fibroblast-like synoviocytes (FLS). Ex vivo analysis of synovial tissue revealed high abundance of IFNγ-producing T cells and NK cells. Similar to marked IFNγ responses in tissue, postinfectious LA synovial fluid also had high levels of IFNγ. HLA-DR-positive FLS were present throughout the synovial lesion, particularly in areas of inflammation. FLS stimulated in vitro with B. burgdorferi, which were similar to conditions during infection, expressed 68 genes associated primarily with innate immune activation and neutrophil recruitment. In contrast, FLS stimulated with IFNγ, which were similar to conditions in the postinfectious phase, expressed >2,000 genes associated with pathogen sensing, inflammation, and MHC Class II antigen presentation, similar to the expression profile in postinfectious synovial tissue. Furthermore, costimulation of FLS with B. burgdorferi and IFNγ induced greater expression of IL-6 and other innate immune response proteins and genes than with IFNγ stimulation alone. These results suggest that B. burgdorferi infection, in combination with IFNγ, initiates the differentiation of FLS into a highly inflammatory phenotype. We hypothesise that overexpression of IFNγ by lymphocytes within synovia perpetuates these responses in the postinfectious period, causing proliferative synovitis and stalling appropriate repair of damaged tissue.

Immune Surveillance Plays a Role in Locally Aggressive Giant Cell Lesions of Bone

BACKGROUND

Giant cell lesions are locally aggressive intraosseous neoplasms with capacity to metastasize. The role of immune surveillance in the pathophysiology of giant cell lesions is poorly understood, and understanding what role the immune system plays in giant cell lesions may lead to the development of more effective treatment. The aim of this study was to explore the role of immune surveillance in giant cell lesions by examining the expression of the HLA class I and class II antigens and tumor infiltrating lymphocytes. In addition, we examined the role of the immune modulating surface antigen B7-H3, which belongs to the B7 superfamily, a group of molecules that modulates T-cell responses.

QUESTIONS/PURPOSES

(1) Is an immune response elicited by giant cell lesions? (2) Do clinically relevant human leukocyte antigen (HLA) defects exist in giant cell lesions? (3) Is B7-H3 a clinically relevant immune modulator?

METHODS

The study sample was derived from the population of patients presenting to the Massachusetts General Hospital for evaluation and management of giant cell lesions from 1993 to 2008. We included patients with histologically confirmed giant cell lesions with a minimum followup of 6 months. Patients with systemic diseases (n = 4 [3%]), syndromes associated with giant cell lesions (n = 4 [3%]), and those without sufficient followup (n = 26 [19%]), inadequate records (n = 7 [5%]), or inadequate tissue available (n = 2 [1%]) were excluded. Tissue microarray, containing 288 tissue cores for 93 patients, was carefully constructed. This contained tissue from 45 patients with maxillofacial lesions, 38 with aggressive and seven with nonaggressive lesions, and 48 patients with axial and appendicular lesions, 30 with aggressive lesions and 18 with nonaggressive lesions. The population mean age was 28 ± 12 years and the duration of followup was 4 ± 3 years. The tissue microarray was immunohistochemically stained with monoclonal antibodies specific for HLA classes I and II and B7-H3 antigens and analyzed for tumor infiltrating lymphocytes. Antigen expression was examined in multinucleated giant cells and mononuclear stromal cells. The results were correlated with local invasion and tumor aggressiveness, which is based on accepted staging criteria.

RESULTS

Tumor infiltrating lymphocytes were detected in all the tumors. The mean number of CD8+ T cell infiltration was lower in aggressive tumors (median, 4.8; interquartile range [IQR], 0.4-13.4), when compared with nonaggressive tumors (median, 15.8; IQR, 4.3-46.3; p = 0.007). HLA class I antigens were highly expressed by multinucleated giant cells in all tumors, but were lightly expressed on mononuclear stromal cells in 53% (45 of 84) to 73% (56 of 77) of tumors. HLA class I antigen low expression in mononuclear stromal cells was associated with tumor aggressiveness (odds ratio [OR], 4.3; p = 0.005). Low HLA class I expression combined with low CD8+ T cell infiltration was most highly associated with tumor aggressiveness (OR, 7.81; p = 0.011). B7-H3 antigen was expressed in 36.9% mononuclear stroma cells and also was associated with local tumor invasion (OR, 1.36; p < 0.001). Similarly, giant cell lesions with high B7-H3 expression and low CD8+ tumor infiltrating lymphocytes were associated with increased tumor aggressiveness (OR, 8.89; p = 0.0491).

CONCLUSIONS

Locally aggressive giant cell lesions are associated with low HLA class 1 antigen expression, low CD8+T cell infiltration, and high expression of the immune modulator B7-H3.

CLINICAL RELEVANCE

Failure of immune surveillance implies that there may be an opportunity to target aspects of the immune surveillance machinery to treat giant cell lesions.

Co-stimulatory and Co-inhibitory Pathways in Autoimmunity

The immune system is guided by a series of checks and balances, a major component of which is a large array of co-stimulatory and co-inhibitory pathways that modulate the host response. Although co-stimulation is essential for boosting and shaping the initial response following signaling through the antigen receptor, inhibitory pathways are also critical for modulating the immune response. Excessive co-stimulation and/or insufficient co-inhibition can lead to a breakdown of self-tolerance and thus to autoimmunity. In this review, we will focus on the role of co-stimulatory and co-inhibitory pathways in two systemic (systemic lupus erythematosus and rheumatoid arthritis) and two organ-specific (multiple sclerosis and type 1 diabetes) emblematic autoimmune diseases. We will also discuss how mechanistic analysis of these pathways has led to the identification of potential therapeutic targets and initiation of clinical trials for autoimmune diseases, as well as outline some of the challenges that lie ahead.

Synovial cellular and molecular markers in rheumatoid arthritis

The profound alterations in the structure, cellular composition, and function of synovial tissue in rheumatoid arthritis (RA) are the basis for the persistent inflammation and cumulative joint destruction that are hallmarks of this disease. In RA, the synovium develops characteristics of a tertiary lymphoid organ, with extensive infiltration of lymphocytes and myeloid cells. Concurrently, the fibroblast-like synoviocytes undergo massive hyperplasia and acquire a tissue-invasive phenotype. In this review, we summarize key components of these processes, focusing on recently-described roles of selected molecular markers of these cellular components of RA synovitis.

The expanding repertoire of targets for immune checkpoint inhibition in bladder cancer: What lies beneath the tip of the iceberg, PD-L1

Over the last decade, a new understanding of tumor-immune system interplay has been ushered in, lead in large part by the discovery of immune checkpoints mediated through B7-CD28 family interactions. Therapeutic blockade of the PD-L1 immune checkpoint pathway has already shown great success as a cancer immunotherapy for advanced urothelial carcinoma, leading to durable clinical remissions in an otherwise incurable disease. There are newly described members of the B7-CD28 family including B7-H3, B7x, and HHLA2. These ligands are thought to play an essential role in suppressing T-cell response, leading to immune tolerance of tumors. This feature makes them attractive targets for novel immunotherapy treatment paradigms. Here, we review the literature of current strategies and future directions of immune checkpoint blockade therapy for bladder cancer.

Different expression of B7-H3 in the caput, corpus, and cauda of the epididymis in mouse

Background

B7-H3, a member of the B7 family of the Ig superfamily of proteins, has been detected in the epididymis, which is a storage organ related to sperm maturation. However, the characteristics of its expression in different regions of the epididymis remain unknown. Our aim was to investigate the expression of B7-H3 in the caput, corpus, and cauda of the epididymis.

Methods

We extracted epididymis specimens from adult male C57BL/6 mice. The expression of B7-H3 was then measured with immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and western blotting.

Results

B7-H3 protein was predominantly detected on the membrane and in the cytoplasm of the principal cells in the epididymis. Moreover, the level of B7-H3 in the corpus of the mouse epididymis was significantly higher than that in the caput (p < 0.05) or the cauda of the epididymis (P < 0.05). However, there was no remarkable difference in the level of B7-H3 between the caput and the cauda (p > 0.05).

Conclusions

The caput, corpus, and cauda of the mouse epididymis all expressed B7-H3 protein. However, the levels of B7-H3 were different in the three regions of the epididymis.

Localization, Shedding, Regulation and Function of Aminopeptidase N/CD13 on Fibroblast like Synoviocytes

Aminopeptidase N/CD13 is highly expressed by fibroblast like synoviocytes (FLS) and may play a role in rheumatoid arthritis (RA). CD13 was previously detected in human synovial fluid where it was significantly increased in RA compared to osteoarthritis. In this study we found that CD13 in biological fluids (plasma, synovial fluid, FLS culture supernatant) is present as both a soluble molecule and on extracellular vesicles, including exosomes, as assessed by differential ultracentrifugation and density gradient separation. Having determined CD13 could be released as a soluble molecule from FLS, we examined potential mechanisms by which CD13 might be shed from the FLS membrane. The use of protease inhibitors revealed that CD13 is cleaved from the FLS surface by metalloproteinases. siRNA treatment of FLS revealed one of those proteases to be MMP14. We determined that pro-inflammatory cytokines (TNFα, IFNγ, IL-17) upregulated CD13 mRNA in FLS, which may contribute to the increased CD13 in RA synovium and synovial fluid. Inhibition of CD13 function by either inhibitors of enzymatic activity or anti-CD13 antibodies resulted in decreased growth and diminished migration of FLS. This suggests that CD13 may be involved in the pathogenic hyperplasia of RA FLS. This data expands potential roles for CD13 in the pathogenesis of RA.

Preferential Induction of the T Cell Auxiliary Signaling Molecule B7-H3 on Synovial Monocytes in Rheumatoid Arthritis

B7-H3, a newly identified B7 family member, has functional duality as a co-stimulator and co-inhibitor that fine-tunes T cell-mediated immune responses. Given that B7-H3 expression on human monocytes and dendritic cells is enhanced by inflammatory cytokines, its potential inmmunoregulatory role at sites of inflammation has been suggested. Further, monocytes play crucial roles in the pathophysiology of various inflammatory disorders including autoimmune diseases; however, the immunological role of B7-H3 in rheumatoid arthritis (RA) has not been defined. Thus, we aimed to investigate the possible roles of monocyte B7-H3 in the pathogenesis of RA. Synovial monocytes, but not peripheral monocytes, in RA patients predominantly express surface B7-H3. The 4Ig isoform of B7-H3 is exclusively induced on the cell surface, whereas the 2Ig B7-H3 isoform is constitutively expressed in the intracytoplasmic region of both peripheral and synovial monocytes. B7-H3 knockdown experiments reveal that surface B7-H3 has an inhibitory effect on IFN-γ production in CD4 memory cells. Moreover, surface B7-H3 expression on synovial monocytes inversely correlates with RA clinical parameters. Our findings demonstrate that activation-induced B7-H3 expression on synovial monocytes has the potential to inhibit Th1-mediated immune responses and immunomodulatory roles affecting RA pathogenesis.

Use of Mesothelial Cells and Biological Matrices for Tissue Engineering of Simple Epithelium Surrogates

Tissue-engineering technologies have progressed rapidly through last decades resulting in the manufacture of quite complex bioartificial tissues with potential use for human organ and tissue regeneration. The manufacture of avascular monolayered tissues such as simple squamous epithelia was initiated a few decades ago and is attracting increasing interest. Their relative morphostructural simplicity makes of their biomimetization a goal, which is currently accessible. The mesothelium is a simple squamous epithelium in nature and is the monolayered tissue lining the walls of large celomic cavities (peritoneal, pericardial, and pleural) and internal organs housed inside. Interestingly, mesothelial cells can be harvested in clinically relevant numbers from several anatomical sources and not less important, they also display high transdifferentiation capacities and are low immunogenic characteristics, which endow these cells with therapeutic interest. Their combination with a suitable scaffold (biocompatible, degradable, and non-immunogenic) may allow the manufacture of tailored serosal membranes biomimetics with potential spanning a wide range of therapeutic applications, principally for the regeneration of simple squamous-like epithelia such as the visceral and parietal mesothelium vascular endothelium and corneal endothelium among others. Herein, we review recent research progresses in mesothelial cells biology and their clinical sources. We make a particular emphasis on reviewing the different types of biological scaffolds suitable for the manufacture of serosal mesothelial membranes biomimetics. Finally, we also review progresses made in mesothelial cells-based therapeutic applications and propose some possible future directions.

B7-H3 expression in breast cancer and upregulation of VEGF through gene silence

B7-H3, a novel member of the B7 family, was previously known as a regulatory ligand regulating T-cell-mediated immune response, and in recent years it was found to take a significant role in various cancers. In some tumor types, high expression of B7-H3 had been linked to a poor prognosis, whereas in other cancers the opposite effect had been observed. The precise role of B7-H3 in tumor immunity is unclear, and further investigations are needed. In the present study, we studied the expression of B7-H3 in the pathologic specimens of 221 patients treated for breast cancer by immunohistochemistry. Strong B7-H3 expression was found in cancer tissues from 80.55% patients, and B7-H3 expression had a negative relation with vascular endothelial growth factor (VEGF) expression, microvascular density for CD34, and tumor size. Furthermore, through lipopolysaccharide-mediated delivery of stable short hairpin ribonucleic acid we observed that silencing of B7-H3 could increase the transcription and secreting of VEGF in breast cancer cell line MCF-7. In summary, the present study demonstrated that B7-H3 suppressed tumor growth through inhibiting VEGF expression. These results increased knowledge of the nonimmunological role of B7-H3 protein and provided novel insights into great biological functions and a putative therapeutic target in breast cancer.

The characteristic expression of B7-H3 and B7-H4 in liver biopsies from patients with HBV-related acute-on-chronic liver failure

Hepatitis B virus (HBV) is a major public health problem, and HBV-related acute-on-chronic liver failure (HBV-ACLF) has an extremely poor prognosis due to a lack of effective treatments. B7-H3 and B7-H4 are two novel members of the B7 superfamily that are actively involved in regulating the pathogenesis of infectious diseases. However, the intrahepatic expression of both members in HBV-ACLF patients has yet to be described. In this study, we analyzed the expression of B7-H3 and B7-H4 in HBV-ACLF biopsies by immunohistochemistry. Our results showed that both members were observed in all HBV-ACLF samples, and their expression was chiefly observed on infiltrating inflammatory cells and the damaged bile ducts. Immunofluorescence double staining showed that B7-H4 was expressed chiefly on CD3(+) T cells, CD68(+) macrophages, CK-18(+) bile ducts, and CD31(+) endothelial cells, while B7-H3 was found on all cell types detected. The expression of the programmed death (PD)-1 ligands, PD-L1 and PD-L2, was also detected in these liver tissues and they were found to be co-expressed with B7-H3 and B7-H4. These results suggest that the B7-family signaling is most likely to affect the pathogenesis of this disease, and a clear understanding of their functional roles may further elucidate the disease process.

T cells and costimulation in cancer

Optimal T cell response is dependent not only on T cell receptor activation, but also on additional signaling from coreceptors. The main coreceptors include B7 and tumor necrosis factor family members. They exert costimulatory or coinhibitory effects, and their balance determines the fate of T cell response. In normal conditions, costimulators facilitate the development of protective immune response, whereas coinhibitors dampen inflammation to avoid organ/tissue damage from excessive immune reaction. In the tumor microenvironment, the balance is garbled: inhibitory pathways predominate, and T cell response is impaired. The importance of cosignaling in the tumor immune response has been experimentally and clinically demonstrated. New therapeutic strategies targeting T cell cosignaling, especially coinhibitory molecules, are under active experimental and clinical investigation. This review summarizes the functions of main T cell cosignaling axes and discusses their clinical application.

Modulation of TNF-induced macrophage polarization by synovial fibroblasts

Mesenchymal stromal cells have emerged as powerful modulators of the immune system. In this study, we explored how the human macrophage response to TNF is regulated by human synovial fibroblasts, the representative stromal cell type in the synovial lining of joints that become activated during inflammatory arthritis. We found that synovial fibroblasts strongly suppressed TNF-mediated induction of an IFN-β autocrine loop and downstream expression of IFN-stimulated genes (ISGs), including chemokines CXCL9 and CXCL10 that are characteristic of classical macrophage activation. TNF induced the production of soluble synovial fibroblast factors that suppressed the macrophage production of IFN-β, and cooperated with TNF to limit the responsiveness of macrophages to IFN-β by suppressing activation of Jak-STAT signaling. Genome-wide transcriptome analysis showed that cocultured synovial fibroblasts modulate the expression of approximately one third of TNF-regulated genes in macrophages, including genes in pathways important for macrophage survival and polarization toward an alternatively activated phenotype. Pathway analysis revealed that gene expression programs regulated by synovial fibroblasts in our coculture system were also regulated in rheumatoid arthritis synovial macrophages, suggesting that these fibroblast-mediated changes may contribute to rheumatoid arthritis pathogenesis. This work furthers our understanding of the interplay between innate immune and stromal cells during an inflammatory response, one that is particularly relevant to inflammatory arthritis. Our findings also identify modulation of macrophage phenotype as a new function for synovial fibroblasts that may prove to be a contributing factor in arthritis pathogenesis.

Generation and characterization of two novel monoclonal antibodies produced against human TLT-2 molecule

Trem-like transcript 2 (TLT-2), one of the TREM family members, which is expressed on B cells, T cells, and macrophages, plays a critical role in immune response mechanism. In this study, two novel mouse anti-human TLT-2 monoclonal antibodies (MAbs) were prepared using hybridoma technology and their immunological characteristics were determined. The results showed that the two MAbs (clones 10F5 and 8C10) were both IgG1 (κ) and bound specifically to human TLT-2. Furthermore, 10F5 and 8C10 seemed to recognize a different site (epitope) of TLT-2 by competition assay. MAb 10F5 was proven in Western blot analysis to specifically bind to denatured TLT-2 protein while both MAbs were proven in dot blot analyses and immunofluorescence to specifically bind to natural TLT-2 protein. In addition, crosslinking of TLT-2 with MAb 8C10 markedly blocked TLT-2 positive signal and T cell proliferation. Taken together, these two monoclonal antibodies might be of great value as tools for further exploration of the expression and function of TLT-2.

Role of major histocompatibility complex class II expression by non-hematopoietic cells in autoimmune and inflammatory disorders: facts and fiction

It is well established that interactions between CD4(+) T cells and major histocompatibility complex class II (MHCII) positive antigen-presenting cells (APCs) of hematopoietic origin play key roles in both the maintenance of tolerance and the initiation and development of autoimmune and inflammatory disorders. In sharp contrast, despite nearly three decades of intensive research, the functional relevance of MHCII expression by non-hematopoietic tissue-resident cells has remained obscure. The widespread assumption that MHCII expression by non-hematopoietic APCs has an impact on autoimmune and inflammatory diseases has in most instances neither been confirmed nor excluded by indisputable in vivo data. Here we review and put into perspective conflicting in vitro and in vivo results on the putative impact of MHCII expression by non-hematopoietic APCs--in both target organs and secondary lymphoid tissues--on the initiation and development of representative autoimmune and inflammatory disorders. Emphasis will be placed on the lacunar status of our knowledge in this field. We also discuss new mouse models--developed on the basis of our understanding of the molecular mechanisms that regulate MHCII expression--that constitute valuable tools for filling the severe gaps in our knowledge on the functions of non-hematopoietic APCs in inflammatory conditions.

NETs are a source of citrullinated autoantigens and stimulate inflammatory responses in rheumatoid arthritis

The early events leading to the development of rheumatoid arthritis (RA) remain unclear, but formation of autoantibodies to citrullinated protein antigens (ACPAs) is considered a key pathogenic event. Neutrophils isolated from patients with various autoimmune diseases display enhanced neutrophil extracellular trap (NET) formation, a phenomenon that exposes autoantigens in the context of immunostimulatory molecules. We investigated whether aberrant NETosis occurs in RA, determined its triggers, and examined its deleterious inflammatory consequences. Enhanced NETosis was observed in circulating and RA synovial fluid neutrophils compared to neutrophils from healthy controls and from patients with osteoarthritis (OA). Further, netting neutrophils infiltrated RA synovial tissue, rheumatoid nodules, and skin. NETosis correlated with ACPA presence and levels and with systemic inflammatory markers. RA sera and immunoglobulin fractions from RA patients with high levels of ACPA and/or rheumatoid factor significantly enhanced NETosis, and the NETs induced by these autoantibodies displayed distinct protein content. Indeed, during NETosis, neutrophils externalized the citrullinated autoantigens implicated in RA pathogenesis, and anti-citrullinated vimentin antibodies potently induced NET formation. Moreover, the inflammatory cytokines interleukin-17A (IL-17A) and tumor necrosis factor-α (TNF-α) induced NETosis in RA neutrophils. In turn, NETs significantly augmented inflammatory responses in RA and OA synovial fibroblasts, including induction of IL-6, IL-8, chemokines, and adhesion molecules. These observations implicate accelerated NETosis in RA pathogenesis, through externalization of citrullinated autoantigens and immunostimulatory molecules that may promote aberrant adaptive and innate immune responses in the joint and in the periphery, and perpetuate pathogenic mechanisms in this disease.

Clinical significance of the induction of macrophage differentiation by the costimulatory molecule B7-H3 in human non-small cell lung cancer

B7-H3, a member of the B7 family of molecules, is expressed in certain types of human cancer and is important in tumor development and progression. Although several studies have reported that the expression of B7-H3 is correlated with poor outcomes in patients with cancer, its exact role in cancer remains unknown. In the present study, the expression levels of B7-H3 in the pathological specimens of 105 patients treated for non-small cell lung cancer (NSCLC) were examined by immunohistochemistry. A high expression level of B7-H3 was observed in 46.9% of the 105 NSCLC tissue specimens. These patients demonstrated a more advanced tumor grade and a shorter survival time. In addition, we also examined the levels of tumor-associated macrophages (TAMs) in NSCLC tissues and observed that the levels were positively correlated with the expression of B7-H3, and that higher levels of macrophages were associated with lower levels of infiltrating T cells and a shorter survival time. These results demonstrated that TAMs are important in the evasion of tumor immune surveillance in NSCLC. Furthermore, through knockdown of B7-H3 by RNA interference, we observed that soluble B7-H3 was capable of inducing macrophages to express higher levels of macrophage mannose receptor (MMR) and lower levels of human leukocyte antigen (HLA)-DR, as well as higher levels of interleukin-10 (IL-10) and lower levels of IL-1β in vitro. These observations are characteristic of an anti-inflammatory/reparatory (alternative/M2) phenotype. Therefore, our data suggests that B7-H3 proteins are involved in the progression of NSCLC by inducing the development of monocytes into anti-inflammatory cells.

Expression of co-stimulatory molecule B7-H4 in patients suffering from rheumatoid arthritis

B7-H4, an inhibitory modulator of T-cell response, is one of the most recently identified cell surface molecules in the B7-CD28 signaling pathway. However, its role in the pathogenesis of rheumatoid arthritis (RA) remains unclear. In the present study, the immunofluorescence staining, confocal laser scanning microscopy and flow cytometry techniques were used to characterize B7-H4 protein expression in RA synovium tissues and peripheral blood mononuclear cell (PBMC) subsets, respectively. Our data showed that the immunolocalization of B7-H4 could be found on the membrane and in the cytoplasm of synoviocytes and CD19(+) B cells in rheumatoid synovium tissues, while B7-H4 was weakly or negatively expressed on CD3(+) T cells, CD14(+) monocytes and CD68(+) macrophages. Moreover, B7-H4 expression was observed in CD34(+) endothelial cells of neovessels in rheumatoid synovium. Flow cytometric analysis also showed that positive B7-H4 expression was found in CD19(+) B cells and CD14(+) monocytes, but not in CD3(+) T cells. Thus, our work identified the expression pattern of B7-H4 in the synovium tissues and PBMC subsets from RA patients, suggesting that B7-H4 involves in the pathological changes of rheumatoid synovium in RA progression, and its detailed biological function needs further investigations.

Autoimmunity and inflammation are independent of class II transactivator type PIV-dependent class II major histocompatibility complex expression in peripheral tissues during collagen-induced arthritis

OBJECTIVE

To determine the regulation of class II major histocompatibility complex (MHC) expression in fibroblast-like synoviocytes (FLS) in order to investigate their role as nonprofessional antigen-presenting cells in collagen-induced arthritis (CIA).

METHODS

Expression of class II MHC, class II MHC transactivator (CIITA), and Ciita isoforms PI, PIII, and PIV was examined by real-time quantitative polymerase chain reaction, immunohistochemistry, and flow cytometry in human synovial tissues, arthritic mouse joints, and human and murine FLS. CIA was induced in mice in which isoform PIV of Ciita was knocked out (PIV(-/-) ), in PIV(-/-) mice transgenic for CIITA in the thymus (K14 CIITA), and in their control littermates.

RESULTS

HLA-DRA, total CIITA, and CIITA PIII messenger RNA levels were significantly increased in synovial tissue samples from patients with rheumatoid arthritis compared with the levels in tissue from patients with osteoarthritis. Human FLS expressed surface class II MHC via CIITA PIII and PIV, while class II MHC expression in murine FLS was entirely mediated by PIV. Mice with a targeted deletion of CIITA PIV lack CD4+ T cells and were protected against CIA. The expression of CIITA was restored in the thymus of PIV(-/-) K14 CIITA-transgenic mice, which had a normal CD4+ T cell repertoire and normal surface levels of class II MHC on professional antigen-presenting cells, but did not induce class II MHC on FLS. Synovial inflammation and immune responses against type II collagen were similar in PIV(-/-) K14 CIITA-transgenic mice and control mice with CIA, but bone erosion was significantly reduced in the absence of PIV.

CONCLUSION

Overexpression of class II MHC is tightly correlated with CIITA expression in arthritic synovium and in FLS. Selective targeting of Ciita PIV in peripheral tissues abrogates class II MHC expression by murine FLS but does not protect against inflammation and autoimmune responses in CIA.

The roles of IFN-γ versus IL-17 in pathogenic effects of human Th17 cells on synovial fibroblasts

OBJECTIVES

Th17 cells, while indispensable in host defense, may play pathogenic roles in many autoimmune diseases, including rheumatoid arthritis (RA). However, the mechanisms by which human Th17 cells drive autoimmunity have not been fully defined. We assessed the potential of the human Th17 CD4 T cell subset to induce expression of cell-cell interaction molecules and inflammatory mediators by fibroblast-like synoviocytes (FLS), and the roles of IFN-γ and IL-17 in these interactions.

METHODS

Th1 or Th17 cells were induced from healthy adult donor CD4 T cells and were co-cultured with FLS for 48 h with/without neutralization of IFN-γ, IL-17A, or both. Alternatively, FLS were treated only with IFN-γ or IL-17 for 48 h. FLS expression of CD40, CD54, and MHC-II, as well as IL-6 and IL-8 secretion, were assessed by surface staining followed by flow cytometry and ELISA, respectively.

RESULTS

Both Th1 and Th17 cells secreted IL-17 as well as IFN-γ, although IFN-γ production was much greater from Th1 cells. FLS expression of CD40, CD54, and MHC-II significantly increased upon co-culture with Th1 cells, while Th17 cells increased only the percentage of FLS that were CD54+. Both T cell subsets induced IL-6 and IL-8 secretion by RA FLS. Neutralization of IL-17A did not reduce FLS expression of CD40, MHC-II, or CD54, but did inhibit IL-6 and IL-8 secretion. Although IFN-γ was a weak inducer of IL-6 secretion and significantly inhibited IL-8 secretion from FLS when used as a single stimulus, neutralization of IFN-γ inhibited the secretion of both cytokines in Th17/FLS co-cultures with RA but not OA FLS.

CONCLUSION

FLS cell-cell interaction molecules and soluble inflammatory mediators are differentially regulated by IFN-γ and IL-17. The effects of IFN-γ may depend in part on the particular milieu of other co-existing cytokines and its potential to induce cell-cell interactions. The potential benefit of therapeutic neutralization of either IL-17 or IFN-γ could depend on the relative proportions of these cytokines in the synovial compartment of an RA patient.

Origination of new immunological functions in the costimulatory molecule B7-H3: the role of exon duplication in evolution of the immune system

B7-H3, a recently identified B7 family member, has different isoforms in human and mouse. Mouse B7-H3 gene has only one isoform (2IgB7-H3) with two Ig-like domains, whereas human B7-H3 has two isoforms (2IgB7-H3 and 4IgB7-H3). In this study a systematic genomic survey across various species from teleost fishes to mammals revealed that 4IgB7-H3 isoform also appeared in pigs, guinea pigs, cows, dogs, African elephants, pandas, megabats and higher primate animals, which resulted from tandem exon duplication. Further sequence analysis indicated that this duplication generated a new conserved region in the first IgC domain, which might disable 4IgB7-H3 from releasing soluble form, while 2IgB7-H3 presented both membrane and soluble forms. Through three-dimensional (3D) structure modeling and fusion-protein binding assays, we discovered that the duplicated isoform had a different structure and might bind to another potential receptor on activated T cells. In T cell proliferation assay, human 2IgB7-H3 (h2IgB7-H3) and mouse B7-H3 (mB7-H3) both increased T cell proliferation and IL-2, IFN-γ production, whereas human 4IgB7-H3 (h4IgB7-H3) reduced cytokine production and T cell proliferation compared to control. Furthermore, both h2IgB7-H3 and mB7-H3 upregulated the function of lipopolysacharide (LPS)-activated monocyte in vitro. Taken together, our data implied that during the evolution of vertebrates, B7-H3 exon duplication contributed to the generation of a new 4IgB7-H3 isoform in many mammalian species, which have carried out distinct functions in the immune responses.

The expression and distribution of immunomodulatory proteins B7-H1, B7-DC, B7-H3, and B7-H4 in rheumatoid synovium

CD28/B7 signals have been shown to have the capacity to regulate T cell activation and participate in regulating the development of rheumatoid arthritis (RA). However, the expression and anatomical distribution of some members of the B7 superfamily including B7-H1, B7-DC, B7-H3 and B7-H4 in RA synovium is still unclear. We analyzed the expression of these molecules in synovial tissues from RA patients. Immunohistochemistry showed that all of these molecules were observed in synovium. On the cellular level, all of them were found on cell membrane and in cytoplasma. The expression of B7-DC and B7-H3 was major on capillaries, synovicytes and infiltrated inflammatory cells in the lining layer, while B7-H1 and B7-H4 were detected in some inflammatory cells residing in the sublining and lining layer. Fluorescent dual staining indicated that all these molecules were principally associated with CD31(+) endothelial cells and CD68(+) macrophages. In addition, B7-H1 and B7-H3 were also observed on CD3(+) T cells (including CD4(+) and CD8(+) T cells). Interestingly, B7-H1/B7-H4, B7-H3/B7-DC were co-expressed on the same cells. The characteristic expression and distribution of these molecules in synovium indicated that they probably have different effects during the progress of RA, and a clear understanding of their functional roles may further elucidate the pathogenesis of this disease.