The role of human T-lymphocyte-monocyte contact in inflammation and tissue destruction

Metabolic signature and proteasome activity controls synovial migration of CDC42hiCD14+ cells in rheumatoid arthritis

Objective

Activation of Rho-GTPases in macrophages causes inflammation and severe arthritis in mice. In this study, we explore if Rho-GTPases define the joint destination of pathogenic leukocytes, the mechanism by which they perpetuate rheumatoid arthritis (RA), and how JAK inhibition mitigates these effects.

Methods

CD14+ cells of 136 RA patients were characterized by RNA sequencing and cytokine measurement to identify biological processes and transcriptional regulators specific for CDC42 hiCD14+ cells, which were summarized in a metabolic signature (MetSig). The effect of hypoxia and IFN-γ signaling on the metabolic signature of CD14+ cells was assessed experimentally. To investigate its connection with joint inflammation, the signature was translated into the single-cell characteristics of CDC42 hi synovial tissue macrophages. The sensitivity of MetSig to the RA disease activity and the treatment effect were assessed experimentally and clinically.

Results

CDC42 hiCD14+ cells carried MetSig of genes functional in the oxidative phosphorylation and proteasome-dependent cell remodeling, which correlated with the cytokine-rich migratory phenotype and antigen-presenting capacity of these cells. Integration of CDC42 hiCD14+ and synovial macrophages marked with MetSig revealed the important role of the interferon-rich environment and immunoproteasome expression in the homeostasis of these pathogenic macrophages. The CDC42 hiCD14+ cells were targeted by JAK inhibitors and responded with the downregulation of immunoproteasome and MHC-II molecules, which disintegrated the immunological synapse, reduced cytokine production, and alleviated arthritis.

Conclusion

This study shows that the CDC42-related MetSig identifies the antigen-presenting CD14+ cells that migrate to joints to coordinate autoimmunity. The accumulation of CDC42 hiCD14+ cells discloses patients perceptive to the JAKi treatment.

New Targets and Strategies for Rheumatoid Arthritis: From Signal Transduction to Epigenetic Aspect

Rheumatoid arthritis (RA) is a chronic autoimmune disease that can lead to joint damage and even permanent disability, seriously affecting patients' quality of life. At present, the complete cure for RA is not achievable, only to relieve the symptoms to reduce the pain of patients. Factors such as environment, genes, and sex can induce RA. Presently, non-steroidal anti-inflammatory drugs, DRMADs, and glucocorticoids are commonly used in treating RA. In recent years, some biological agents have also been applied in clinical practice, but most have side effects. Therefore, finding new mechanisms and targets for treating RA is necessary. This review summarizes some potential targets discovered from the perspective of epigenetics and RA mechanisms.

The Role of M1/M2 Macrophage Polarization in Rheumatoid Arthritis Synovitis

Innate and adaptive immunity represent a harmonic counterbalanced system involved in the induction, progression, and possibly resolution of the inflammatory reaction that characterize autoimmune rheumatic diseases (ARDs), including rheumatoid arthritis (RA). Although the immunopathophysiological mechanisms of the ARDs are not fully clarified, they are often associated with an inappropriate macrophage/T-cell interaction, where classical (M1) or alternative (M2) macrophage activation may influence the occurrence of T-helper (Th)1 or Th2 responses. In RA patients, M1/Th1 activation occurs in an inflammatory environment dominated by Toll-like receptor (TLR) and interferon (IFN) signaling, and it promotes a massive production of pro-inflammatory cytokines [i.e., tumor necrosis factor-α (TNFα), interleukin (IL)-1, IL-12, IL-18, and IFNγ], chemotactic factors, and matrix metalloproteinases resulting in osteoclastogenesis, erosion, and progressive joint destruction. On the other hand, the activation of M2/Th2 response determines the release of growth factors and cytokines [i.e., IL-4, IL-10, IL-13, and transforming growth factor (TGF)-β] involved in the anti-inflammatory process leading to the clinical remission of RA. Several subtypes of macrophages have been described. Five polarization states from M1 to M2 have been confirmed in in vitro studies analyzing morphological characteristics, gene expression of phenotype markers (CD80, CD86, TLR2, TLR4, or CD206, CD204, CD163, MerTK), and functional aspect, including the production of reactive oxygen species (ROS). An M1 and M2 macrophage imbalance may induce pathological consequences and contribute to several diseases, such as asthma or osteoclastogenesis in RA patients. In addition, the macrophage dynamic polarization from M1 to M2 includes the presence of intermediate polarity stages distinguished by the expression of specific surface markers and the production/release of distinct molecules (i.e., nitric oxide, cytokines), which characterize their morphological and functional state. This suggests a “continuum” of macrophage activation states playing an important role during inflammation and its resolution. This review discusses the importance of the delicate M1/M2 imbalance in the different phases of the inflammatory process together with the identification of specific pathways, cytokines, and chemokines involved, and its clinical outcomes in RA. The analysis of these aspects could shed a light on the abnormal inflammatory activation, leading to novel therapeutical approaches which may contribute to restore the M1/M2 balance.

Stimulation of the PD-1 Pathway Decreases Atherosclerotic Lesion Development in Ldlr Deficient Mice

Aim: Signaling through the coinhibitory programmed death (PD)-1/PD-L1 pathway regulates T cell responses and can inhibit ongoing immune responses. Inflammation is a key process in the development of atherosclerosis, the underlying cause for the majority of cardiovascular diseases. Dampening the excessive immune response that occurs during atherosclerosis progression by promoting PD-1/PD-L1 signaling may have a high therapeutic potential to limit disease burden. In this study we therefore aimed to assess whether an agonistic PD-1 antibody can diminish atherosclerosis development.

Methods and Results: Ldlr^−/− mice were fed a western-type diet (WTD) while receiving 100 μg of an agonistic PD-1 antibody or control vehicle twice a week. Stimulation of the PD-1 pathway delayed the WTD-induced monocyte increase in the circulation up to 3 weeks and reduced T cell activation and proliferation. CD4⁺ T cell numbers in the atherosclerotic plaque were reduced upon PD-1 treatment. More specifically, we observed a 23% decrease in atherogenic IFNγ-producing splenic CD4⁺ T cells and a 20% decrease in cytotoxic CD8⁺ T cells, whereas atheroprotective IL-10 producing CD4⁺ T cells were increased with 47%. Furthermore, we found an increase in regulatory B cells, B1 cells and associated atheroprotective circulating oxLDL-specific IgM levels in agonistic PD-1-treated mice. This dampened immune activation following agonistic PD-1 treatment resulted in reduced atherosclerosis development (p < 0.05).

Conclusions: Our data show that stimulation of the coinhibitory PD-1 pathway inhibits atherosclerosis development by modulation of T- and B cell responses. These data support stimulation of coinhibitory pathways as a potential therapeutic strategy to combat atherosclerosis.

TRAM-Related TLR4 Pathway Antagonized by IRAK-M Mediates the Expression of Adhesion/Coactivating Molecules on Low-Grade Inflammatory Monocytes

Low-grade inflammatory monocytes critically contribute to the pathogenesis of chronic inflammatory diseases such as atherosclerosis. The elevated expression of coactivating molecule CD40 as well as key adhesion molecule CD11a is a critical signature of inflammatory monocytes from both human patients with coronary artery diseases as well as in animal models of atherosclerosis. In this study, we report that subclinical superlow-dose LPS, a key risk factor for low-grade inflammation and atherosclerosis, can potently trigger the induction of CD40 and CD11a on low-grade inflammatory monocytes. Subclinical endotoxin-derived monocytes demonstrate immune-enhancing effects and suppress the generation of regulatory CD8+CD122+ T cells, which further exacerbate the inflammatory environment conducive for chronic diseases. Mechanistically, subclinical endotoxemia activates TRAM-mediated signaling processes, leading to the activation of MAPK and STAT5, which is responsible for the expression of CD40 and CD11a. We also demonstrate that TRAM-mediated monocyte polarization can be suppressed by IRAK-M. IRAK-M-deficient monocytes have increased expression of TRAM, elevated induction of CD40 and CD11a by subclinical-dose endotoxin, and are more potent in suppressing the CD8 regulatory T cells. Mice with IRAK-M deficiency generate an increased population of inflammatory monocytes and a reduced population of CD8 T regulatory cells. In contrast, mice with TRAM deficiency exhibit a significantly reduced inflammatory monocyte population and an elevated CD8 T regulatory cell population. Together, our data reveal a competing intracellular circuitry involving TRAM and IRAK-M that modulate the polarization of low-grade inflammatory monocytes with an immune-enhancing function.

Cytokines TNFα, IFNγ and IL-2 Are Responsible for Signal Transmission from the Innate Immunity Protein Tag7 (PGLYRP1) to Cytotoxic Effector Lymphocytes

Studies on the mechanisms of activation of cytotoxic lymphocyte subpopulations are an important research direction in modern immunology. This study provides a detailed analysis of the effect of Tag7 (PGRP-S, PGLYRP1) on the development of lymphocyte subpopulations cytotoxic against MHC-negative tumor cells in a pool of peripheral blood mononuclear cells (PBMCs). The results show that Tag7 can bind to the TREM-1 receptor on the surfaces of monocytes, thereby triggering the expression of mRNA TNFα and IFNγ. The appearance of these cytokines in conditioned medium leads to IL-2 cytokine secretion by CD3⁺CD4⁺ lymphocytes. In turn, IL-2 facilitates unspecific activation of three cytotoxic cell subpopulations in the PBMC pool: NK (CD16⁺CD56⁺), CD3⁺CD4⁺ and CD3⁺CD8⁺. These subpopulations appear after a certain period of incubation with Tag7 and show toxicity against tumor cells.

Fibronectin Fragments and Inflammation During Canine Intervertebral Disc Disease

Background: Canine intervertebral disc disease (IVDD) represents a significant clinical problem in veterinary medicine, with similarities to the human pathology. Host-derived damage-associated molecular patterns like fibronectin fragments (FnF) that develop during tissue dysfunction may be of specific relevance to IVD pathologies by inducing an inflammatory response in resident cells. Aim: This project aimed to determine the presence and pathobiological role of FnF during IVD herniation in dogs, with a focus on inflammation. Methods: Herniated nucleus pulposus (NP) material from five dogs as well as non-herniated adjacent NP material from three dogs was collected during spinal surgery required due to acute IVD herniation. The presence of different types of FnF were determined by Western blot analysis. NP cells isolated from six herniated canine IVDs were then exposed to 30 kDa FnF. NP cell inflammation and catabolism was examined by investigating the expression of IL-1β, IL-6, IL-8, and COX-2, as well as MMP-1 and MMP-3 by qPCR (all targets) and ELISA (IL-6, PGE₂). Results: Amongst multiple sized FnF (30, 35, 45, and >170kDa), N-terminal fragments at a size of ~30 kDa were most consistently expressed in all five herniated IVDs. Importantly, these fragments were exclusively present in herniated, but not in non-herniated IVDs. Exposure of canine NP cells to 500 nM 30 kDa FnF caused a significant upregulation of IL-6 (62.5 ± 79.9, p = 0.032) and IL-8 (53.0 ± 75.7, p = 0.031) on the gene level, whereas IL-6 protein analysis was inconclusive. Donor-donor variation was observed in response to FnF treatment, whereby this phenomenon was most evident for COX-2, with three donors demonstrating a significant downregulation (0.67 ± 0.03, p = 0.003) and three donors showing upregulation (6.9 ± 5.5, p = 0.21). Co-treatment with Sparstolonin B, a TRL-2/TRL-4 antagonist, showed no statistical difference to FnF treatment alone in all tested target genes. Conclusion: Given the presence of the 30 kDa FnF in canine herniated IVDs and the proinflammatory effect of 30 kDa FnF on NP cells, we concluded that the accumulation of FnF may be involved in the pathogenesis of canine IVDD. These results correspond to the findings in humans with IVDD.

Impact of Immunoglobulin M-Type Donor-Specific Human Leukocyte Antigen-Antibody Levels in Supernatants from Cultured Peripheral Blood Mononuclear Cells as Predictors of Antibody-Mediated Rejection

Background: Antibody-mediated rejection (AMR) is a crucial barrier in the long-term prognosis of transplant recipients. Methods: Peripheral blood mononuclear cells (PBMCs) were collected from kidney allograft recipients (N = 41) and cultured in vitro for 1 week. Furthermore, the supernatants of the cultured PBMCs were analyzed by Luminex single-antigen beads. Results: Analyses using Luminex single-antigen beads revealed the presence of immunoglobulin (Ig) G donor-specific anti-HLA antibodies (DSAs) was detected in the supernatants of cultured PBMCs collected more frequently than IgM in de novo DSA-sensitized patients with AMR, and IgM were detectable in patients with stable graft function mainly and several IgM DSAs were detectable in the supernatants of the cultured PBMCs before detecting the IgG levels in sera. We also found that the DSA-specific IgM-secreting memory B cells (mBCs) were more sensitive to the chronic use of immunosuppressive agents than to the IgG-secreting mBCs. Conclusions: In the transplant recipients, the assessment of supernatants of cultured PBMCs provide more details of immune reactions than the commonly used method that directly measures IgG DSA levels in patient sera and some IgM DSA detection may be a better predictor of IgG DSAs production, which may cause AMR and enable early intervention, in initial stages of AMR development.

The model of cytokine release syndrome in CAR T-cell treatment for B-cell non-Hodgkin lymphoma

Chimeric antigen receptor T (CAR T) cell therapy has demonstrated efficacy in the treatment of haematologic malignancies. However, the accompanying adverse events, the most common of which is cytokine release syndrome (CRS), substantially limit its wide application. Due to its unique physiological characteristics, CRS in CAR T-cell treatment for B-cell non-Hodgkin lymphoma (B-NHL) may exhibit some special features. Although existing guidelines had greatly promoted the recognition and management of CRS, many recommendations are not fully applicable to B-NHL. Therefore, it is imperative to identify responses that are specific to CRS observed following CAR T treatment for B-NHL. Based on underlying biological processes and known pathophysiological mechanisms, we tentatively propose a new model to illustrate the occurrence and evolution of CAR T-cell-therapy-related CRS in B-NHL. In this model, tumour burden and bone marrow suppression are considered determinants of CRS. Novel phenomena after CAR T-cell infusion (such as local inflammatory response) are further identified. The proposed model will help us better understand the basic biology of CRS and recognize and manage it more rationally.

The effect of lipoxin A4 on E. coli LPS-induced osteoclastogenesis

Objectives

The objective of the present study was to investigate the effect of lipoxin-type A4 (LXA4) on bacterial-induced osteoclastogenesis.

Material and methods

Human periodontal ligament cells (PDLCs) in coculture with osteoclast precursors (RAW264.7 cells) were exposed to bacterial stimulation with lipopolysaccharide (LPS) to induce inflammation. After 24 h, cells were treated to 100 ng/ml of LXA4 and 50 ng/ml of forymul peptide receptor 2 (FPR2/ALX) receptor antagonist (Boc-2). After 5 days, osteoclastic resorptive activity was assessed on calcium phosphate (CaP) synthetic bone substitute. Additionally, osteoclastic differentiation was evaluated using tartrate-resistant acid phosphatase (TRAP) staining, TRAP enzymatic activity assay, and on the expression of osteoclast-specific genes.

Results

We found that stimulation of in the osteoclasts with LPS-stimulated PDLCs induced a significant increase in tartrate-resistant acid phosphatase (TRAP) positive cells, higher resorptive activity, and enhanced expression of specific genes. Meanwhile, LXA4-treatment exhibited strong anti-inflammatory activity, and was able to reverse these inflammatory effects.

Conclusions

We conclude that (1) PDLCs are a potential target for treating bacterial-induced bone resorption in patients with periodontal disease, and (2) LXA4 is a suitable candidate for such therapy.

Clinical relevance

The results prove that lipoxins have a protective role in bacterial-induced periodontal inflammation and alveolar bone resorption, which can be translated into a clinical beneficial alterative treatment.

The role of microbiome in rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is an autoimmune disorder with multifactorial etiology; both genetic and environmental factors are known to be involved in pathogenesis. Treatment with disease-modifying antirheumatic drugs (DMARDs) plays an essential role in controlling disease progression and symptoms. DMARDs have immunomodulatory properties and suppress immune response by interfering in various pro-inflammatory pathways. Recent evidence has shown that the gut microbiota directly and indirectly modulates the host immune system. RA has been associated with dysbiosis of the gut microbiota. Patients with RA treated with DMARDs show partial restoration of eubiotic gut microbiome. Hence, it is essential to understand the impact of DMARDs on the microbial composition and its consequent influences on the host immune system to identify novel therapies for RA. In this review, we discuss the importance of antirheumatic-drug-induced host microbiota modulations and possible probiotics that can generate eubiosis.

The many facets of macrophages in rheumatoid arthritis

Macrophages are central to the pathophysiology of rheumatoid arthritis (RA). They constitute the main source of pro-inflammatory cytokines and chemokines such as TNF and IL-1β, they activate a wide range of immune and non-immune cells, and they secrete diverse tissue degrading enzymes driving chronic pro-inflammatory, tissue destructive and pain responses in RA. However, they can also produce anti-inflammatory cytokines such as IL-10, secrete inhibitors of tissue degrading enzymes and promote immunoregulatory and protective responses, suggesting the existence of macrophages with distinct and diverse functional activities. Although the underlying basis of this phenomenon has remained obscure for years, emerging evidence has now provided insight into the mechanisms and molecular processes involved. Here, we review current knowledge on the biology of macrophages in RA, and highlight recent literature on the heterogeneity, origins and ontogeny of macrophages as part of the mononuclear phagocyte system. We also discuss their plasticity in the context of the M1/M2 paradigm, and the emerging theme of metabolic rewiring as a major mechanism for programming macrophage functions and pro-inflammatory activities. This sheds light into the many facets of macrophages in RA, their molecular regulation and their translational potential for developing novel protective and therapeutic strategies in the clinic.

Immunopathogenic Mechanisms and Novel Immune-Modulated Therapies in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disease of unknown etiology. It is characterized by the presence of rheumatoid factor and anticitrullinated peptide antibodies. The orchestra of the inflammatory process among various immune cells, cytokines, chemokines, proteases, matrix metalloproteinases (MMPs), and reactive oxidative stress play critical immunopathologic roles in the inflammatory cascade of the joint environment, leading to clinical impairment and RA. With the growing understanding of the immunopathogenic mechanisms, increasingly novel marked and potential biologic agents have merged for the treatment of RA in recent years. In this review, we focus on the current understanding of pathogenic mechanisms, highlight novel biologic disease-modifying antirheumatic drugs (DMRADs), targeted synthetic DMRADs, and immune-modulating agents, and identify the applicable immune-mediated therapeutic strategies of the near future. In conclusion, new therapeutic approaches are emerging through a better understanding of the immunopathophysiology of RA, which is improving disease outcomes better than ever.

Differences of the Structure of Immune Regulatory Cell Populations between Cellular Material from Sonographically Detected Focal Thyroid Lesions and Peripheral Blood in Humans

Focal thyroid lesions are common ultrasound findings with the estimated prevalence up to 67% of the population. They form characteristically enveloped regions with individual encapsulated microenvironment that may involve the specific distribution of immune system compounds—especially antigen presenting cells (APC). We analyzed and compared the most potent APC—plasmacytoid and conventional dendritic cells (DCs) subpopulations and three monocyte subpopulations as well as other immune cells—in peripheral blood and local blood of thyroid gland obtained parallelly in patients with focal thyroid lesions using flow cytometry. The analysis revealed significant differences in the distribution of main subsets of assessed cells between peripheral blood and biopsy material. The results support the existence of local, organ-specific immune reaction control networks within thyroid nodules.

Ontology and Function of Fibroblast-Like and Macrophage-Like Synoviocytes: How Do They Talk to Each Other and Can They Be Targeted for Rheumatoid Arthritis Therapy?

Fibroblast-like synoviocytes (FLS) and macrophage-like synoviocytes (MLS) are the two main cellular components of the synovium. It has been widely reported that FLS and MLS play essential roles in the joint pathology of rheumatoid arthritis (RA). Although various studies have analyzed both human and animal tissues and have shown that both cell types are involved in different stages of RA, ontology, and specific functions of both cell populations and their interactions are not well understood. In this review, we will summarize recent research on FLS and MLS in RA and focus on the development and function of two predominant synovial cell types. In addition, we will discuss the communication between FLS or MLS and highlight potential treatments for RA that involve synoviocytes.

From supernatants to cytokines: a personal view on the early history of IL-1, IL-1Ra, TNF and its inhibitor in rheumatology

Long-term cell cultures developed early in the twentieth century allowed identification in their supernatants of biological mediators subsequently defined as migration factors, interferons, lymphokines, monokines, cytokines and interleukins. In rheumatology, early in the 1930s, synovial cell cultures revealed two major distinct populations, i.e. synovial fibroblasts and monocyte-macrophages. Discovery of the interstitial collagenase (MMP-1) and its role in tissue destruction, such as in rheumatoid arthritis (RA), raised the question of the cellular source for this enzyme. My personal interest in the field was driven by the lack of understanding for the link between tissue destruction and immunology. This triggered our seminal contribution to the field, establishing in 1976-79 at the Arthritis Unit (Massachusetts General Hospital, with SM Krane) that a mononuclear factor (MCF, around 15 kDa) produced by stimulated macrophage, under direct contact with activated T cells, induced large amounts of collagenase and prostaglandin E2 (PGE2, a bone resorbing agent) in human synovial fibroblasts from RA patients. Our original "MCF" biological observations preceded cloning, and recombinant IL-1β confirmed the biological activity of the purified natural IL-1. Following my return to Geneva in 1980 and searching for a high level of IL-1 in urine and serum of patients with high fever or Still's disease, to our surprise-"a finding of absence"-we found that IL-1 was masked by a factor of approximately 17 kDa and first presented this in 1984 at the Fourth International Lymphokine Workshop. In 1987, before IL-Ra cloning, my co-worker P Seckinger and I demonstrated first-time observation in cytokine biology that the mechanism was due to the inhibition of IL-1 binding the cell surface receptor, leading to the concept of IL-1 receptor antagonist (IL-1Ra). Having reported in 1985 that TNF/cachectin also induced collagenase and PGE2 in human synovial cells, we found that IL-1Ra did not block TNF-α but was due to another inhibitor. As other investigators, we confirmed that this inhibitory factor was a soluble TNF receptor. The years between the 1970s and 1990s were probably the most exciting period in the field of cytokines and cytokine antagonists; it gave rise to two concepts in the cytokine field-one of the receptor antagonist, and the other of soluble receptor antagonists.

Inflammatory pattern of the infrapatellar fat pad in dogs with canine cruciate ligament disease

BACKGROUND

Despite the importance of inflammation during the pathogenesis of cranial cruciate ligament disease (CCLD) in dogs and despite the latest knowledge suggesting a significant role of adipose tissue in osteoarthritis, the infrapatellar fat pad (IFP) was up to now mostly disregarded in veterinary investigations. In the present study, the inflammatory activity of the IFP, the main adipose structure within the stifle joint, was thoroughly investigated to evaluate its potential impact in the pathogenesis of this common disease of our canine companions. Samples of IFP, subcutaneous adipose tissue (ScAT) of the thigh and synovial fluid in both diseased (n = 36) and healthy control (n = 23) dogs were tested for their immune cell composition but also for interleukins (IL-1β, IL-6, IL-8, IL-10), degradative enzymes (MMP-1, MMP-3, MMP-13, TIMP-2, iNOS) and adipokines (leptin and adiponectin). Characterization of the immune cell composition was ascertained by fluorescence activated cell sorting. Gene expression and protein release of the inflammatory markers was determined by real RT-qPCR and ELISA.

RESULTS

IFPs of dogs with CCLD had a significantly increased immune cell count with T cells (CD3) as the most abundant immune cells. T cells and macrophages (CD14) were significantly increased compared to healthy controls or corresponding ScAT. In addition, IFPs of dogs with CCLD demonstrated a significant increase on gene as well as protein level of multiple inflammatory indicators (IL-1β, IL-6, MMP-1, MMP-13) compared to the other tissues. TNFα was only increased on gene expression. Adipokine analysis showed higher secretion of adiponectin and lower leptin secretion in IFP from dogs with CCLD than from controls. In the synovial fluid from dogs with CCLD concentrations of IL-1β, MMP-1, MMP-13 as well as leptin were significantly increased compared to the synovial fluid from healthy control dogs.

CONCLUSIONS

The present study indicates that the IFP is a potential contributory factor in the pathogenesis of CCLD, due to its inflammatory phenotype and the proximity within the stifle joint. To determine the extent of this possible inter-relationship, further studies need to be undertaken.

Forward and Reverse Signaling Mediated by Transmembrane Tumor Necrosis Factor-Alpha and TNF Receptor 2: Potential Roles in an Immunosuppressive Tumor Microenvironment

Tumor necrosis factor-alpha (TNF-α) is a pleiotropic inflammatory cytokine produced mainly by activated macrophages, lymphocytes and other cell types. Two distinct forms of TNF-α have been identified: soluble TNF-α (sTNF-α) and transmembrane TNF-α (mTNF-α). mTNF-α, which is the precursor of sTNF-α, can be cleaved by the TNF-α converting enzyme (TACE) and is released as sTNF-α. sTNF-α binds primarily to TNF receptor 1 (TNFR1) and plays an important role in the inflammatory immune response, whereas mTNF-α interacts primarily with TNF receptor 2 (TNFR2) and mediates the promotion of cellular proliferation and survival and other biological effects. It has been reported that the interaction between mTNF-α and TNFR2 induces bi-directional (forward and reverse) signaling in both mTNF-α- and TNFR2-expressing cells. Increasing evidence shows that the forward and reverse signaling mediated by mTNF-α and TNFR2 might play a significant role in the tumor microenvironment. In this review, the role of the crosstalk between mTNF-α and TNFR2 in the tumor microenvironment will be discussed.

Cellular and molecular perspectives in rheumatoid arthritis

Synovial immunopathology in rheumatoid arthritis is complex involving both resident and infiltrating cells. The synovial tissue undergoes significant neovascularization, facilitating an influx of lymphocytes and monocytes that transform a typically acellular loose areolar membrane into an invasive tumour-like pannus. The microvasculature proliferates to form straight regularly-branching vessels; however, they are highly dysfunctional resulting in reduced oxygen supply and a hypoxic microenvironment. Autoantibodies such as rheumatoid factor and anti-citrullinated protein antibodies are found at an early stage, often before arthritis has developed, and they have been implicated in the pathogenesis of RA. Abnormal cellular metabolism and mitochondrial dysfunction thus ensue and, in turn, through the increased production of reactive oxygen species actively induce inflammation. Key pro-inflammatory cytokines, chemokines and growth factors and their signalling pathways, including nuclear factor κB, Janus kinase-signal transducer, are highly activated when immune cells are exposed to hypoxia in the inflamed rheumatoid joint show adaptive survival reactions by activating. This review attempts to highlight those aberrations in the innate and adaptive immune systems including the role of genetic and environmental factors, autoantibodies, cellular alterations, signalling pathways and metabolism that are implicated in the pathogenesis of RA and may therefore provide an opportunity for therapeutic intervention.

Serum apoprotein A1 levels are inversely associated with disease activity in gout: From a southern Chinese Han population

To analyze the alteration of lipid profile and inflammatory markers in the serum of patients with gouty arthritis (GA), the levels of serum lipid profile, C-reactive protein (CRP), and erythrocyte sedimentation rates (ESRs) were measured in the serum of 69 gout patients, 35 patients with rheumatoid arthritis (RA), 23 patients with ankylosing spondylitis (AS)/spondyloarthropathy (SpA), and 25 patients with osteoarthritis (OA). The serum levels of apoprotein A1 (Apo-A1) were significantly decreased in patients with gout when compared with RA, AS/SpA, and OA patients. The serum levels of CRP were significantly increased in gouty patients when compared with RA, AS/SpA, and OA patients. Furthermore, the serum levels of ESR were significantly increased in patients with gout compared to patients with OA. Correlation analysis indicated that the levels of Apo-A1 were negatively correlated with serum ESR and CRP (r = -0.475, P < .001; r = -0.380, P = .001, respectively) in the patients with GA. Taken together, this study gives us a better understanding of the relationships between serum lipid profile and inflammatory markers in gout patients.

The Interplay Between Monocytes/Macrophages and CD4(+) T Cell Subsets in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by inflammation of the synovial lining (synovitis). The inflammation in the RA joint is associated with and driven by immune cell infiltration, synovial hyperproliferation, and excessive production of proinflammatory mediators, such as tumor necrosis factor α (TNFα), interferon γ (IFNγ), interleukin (IL)-1β, IL-6, and IL-17, eventually resulting in damage to the cartilage and underlying bone. The RA joint harbors a wide range of immune cell types, including monocytes, macrophages, and CD4(+) T cells (both proinflammatory and regulatory). The interplay between CD14(+) myeloid cells and CD4(+) T cells can significantly influence CD4(+) T cell function, and conversely, effector vs. regulatory CD4(+) T cell subsets can exert profound effects on monocyte/macrophage function. In this review, we will discuss how the interplay between CD4(+) T cells and monocytes/macrophages may contribute to the immunopathology of RA.

TLR costimulation causes oxidative stress with unbalance of proinflammatory and anti-inflammatory cytokine production

IL-1β acts in concert with anti-inflammatory cytokines, in particular, IL-1R antagonist (IL-1Ra), to ensure the correct development and outcome of the inflammation: imbalance in the IL-1β/IL-1Ra ratio is implicated in many human diseases and may lead to dramatic consequences. In this article, we show that single TLR engagement induces IL-1β and, with a little delay, IL-1Ra. Differently, costimulation of TLR2, TLR4, and TLR7/8 enhances IL-1β secretion but severely inhibits IL-1Ra production. The IL-1β/IL-1Ra unbalance after activation of multiple TLRs depends on the insurgence of oxidative stress, because of enhanced production of reactive oxygen species and failure of the antioxidant systems. Increased reactive oxygen species levels increase ATP externalization by monocytes, resulting in enhanced inflammasome activation and IL-1β secretion. Oxidative stress then induces cell responses to stress, including inhibition of protein synthesis, which, in turn, is responsible for the impaired production of IL-1Ra. IL-1Ra secretion is restored by exogenous antioxidants that oppose oxidative stress. Similar effects are evident also on other cytokines: TNF-α is induced, whereas IL-6 is inhibited by costimulation. Our findings provide a molecular basis to the imbalance between proinflammatory and regulatory cytokine circuits that occur in various pathologic conditions, and suggest new strategies for controlling inflammation.

Targeting monocytes/macrophages in the treatment of rheumatoid arthritis

Biotherapies have revolutionized the treatment of RA. However, much work is needed to understand all the mechanisms of these biotherapies, and alternatives are needed to circumvent adverse effects and the high cost of these long-lasting treatments. In this article we outline some of the approaches we have used to target monocytes/macrophages as major components of inflammation and bone homeostasis. We also discuss how anti-TNF-α antibodies target monocytes/macrophages in the complex mechanisms contributing to inhibition of inflammation.

FAS/FAS-L dependent killing of activated human monocytes and macrophages by CD4+CD25- responder T cells, but not CD4+CD25+ regulatory T cells

Conclusive resolution of an immune response is critical for the prevention of autoimmunity and chronic inflammation. We report that following co-culture with autologous CD4+CD25- responder T cells, human CD14+ monocytes and monocyte-derived macrophages become activated but also significantly more prone to apoptosis than monocytes/macrophages cultured alone. In contrast, in the presence of CD4+CD25+ regulatory T cells (Tregs), monocytes and macrophages survive whilst adopting an anti-inflammatory phenotype. The induction of monocyte death requires responder T cell activation and cell-contact between responder T cells and monocytes. We demonstrate a critical role for FAS/FAS-L ligation in responder T cell-induced monocyte killing since responder T cells, but not Tregs, upregulate FAS-ligand (FAS-L) mRNA, and induce FAS expression on monocytes. Furthermore, responder T cell-induced monocyte apoptosis is blocked by neutralising FAS/FAS-L interaction, and is not observed when monocytes from an autoimmune lymphoproliferative syndrome (ALPS) patient with complete FAS-deficiency are used as target cells. Finally, we show that responder T cell-induced killing of monocytes is impaired in patients with active rheumatoid arthritis (RA). Our data suggest that resolution of inflammation in the course of a healthy immune response is aided by the unperturbed killing of monocytes with inflammatory potential by responder T cells and the induction of longer-lived, Treg-induced, anti-inflammatory monocytes.

The influence of interleukin-4 on ligament healing

Despite a complex cascade of cellular events to reconstruct the damaged extracellular matrix, ligament healing results in a mechanically inferior scarred ligament. During normal healing, granulation tissue expands into any residual normal ligamentous tissue (creeping substitution), resulting in a larger region of healing, greater mechanical compromise and an inefficient repair process. To control creeping substitution and possibly enhance the repair process, the antiinflammatory cytokine, interleukin-4 (IL-4), was administered to rats before and after rupture of their medial collateral ligaments. In vitro experiments showed a time-dependent effect on fibroblast proliferation after IL-4 treatment. In vivo treatments with IL-4 (100 ng/mL IV) for 5 days resulted in decreased wound size and type III collagen and increased type I procollagen, indicating a more regenerative early healing in response to the IL-4 treatment. However, continued treatment of IL-4 to day 11 antagonized this early benefit and slowed healing. Together, these results suggest that IL-4 not only influences the macrophages and T lymphocytes but also stimulates fibroblasts associated with the proliferative phase of healing in a dose-, cell-, and time-dependent manner. Although treatment significantly influenced healing in the first week after injury, IL-4 alone was unable to maintain this early regenerative response.

Hyaluronan inhibits Akt, leading to nuclear factor-κB down-regulation in lipopolysaccharide-stimulated U937 macrophages

Hyaluronan (HA) of high molecular weight is used in the treatment of osteoarthritis and rheumatoid arthritis by intra-articular injection. While HA has been shown to suppress nuclear factor (NF)-κB activation by proinflammatory cytokines and lipopolysaccharide (LPS), intracellular upstream events that cause NF-κB down-regulation in response to HA remain unclear. Thus, this study was performed to investigate the involvement of phosphoinositide-3-OH kinase (PI3K)/Akt in the inhibition of the LPS-activated NF-κB pathway by HA in U937 macrophages. In adherent U937 macrophage cultures, pretreatment with HA of 2700 kDa (1 mg/ml, 1 h) significantly inhibited interleukin-6 (IL-6) production by LPS (200 ng/ml, 24 h)-stimulated U937 cells. LPS (200 ng/ml) activated Akt and NF-κB, whereas HA (1 mg/ml) down-regulated LPS-stimulated phosphorylation of Akt and NF-κB. Inhibition studies using LY294002 (20 µM) revealed the requirement of the PI3K/Akt pathway for LPS-stimulated IL-6 production and NF-κB activation. Pretreatment with anti-intercellular adhesion molecule-1 (ICAM-1) antibody (20 µg/ml) reversed the inhibitory effects of HA on LPS-induced production of IL-6 and activation of Akt and NF-κB. Herein, we provided the first evidence that HA suppresses the LPS-activated PI3K/Akt pathway, leading to down-regulation of NF-κB with diminished IL-6 production through interaction with ICAM-1.

Gene expression profiles in peripheral blood for the diagnosis of autoimmune diseases

Gene expression profiling in clinical genomics has yet to deliver robust and reliable approaches for developing diagnostics and contributing to personalized medicine. Owing to technological developments and the recent accumulation of expression profiles, it is a timely and relevant question whether peripheral blood gene expression profiling can be used routinely in clinical decision making. Here, we review the available gene expression profiling data of peripheral blood in autoimmune and chronic inflammatory diseases and suggest that peripheral blood mononuclear cells are suitable for descriptive and comparative gene expression analyses. A gene-disease interaction network in chronic inflammatory diseases, a general protocol for future studies and a decision tree for researchers are presented to facilitate standardization and adoption of this approach.

Plasma levels of apolipoprotein A1 in malaria-exposed primigravidae are associated with severe anemia

Background

Plasmodium falciparum placental malaria (PM) contributes to 10,000 maternal deaths due to severe anemia (SA) each year in Africa, primarily among primigravid women who are most susceptible. Increased levels of proinflammatory cytokines like TNF-α are associated with maternal anemia in first time mothers but not in other women. Here we aimed to identify additional changes in the plasma proteome associated with pregnancy malaria that may contribute to the development of malaria-related maternal anemia.

Principal Findings

A semi-quantitative mass spectrometry approach was used to compare the relative abundance of plasma proteins in anemic versus non-anemic women with PM. Levels of 24 proteins differed significantly between anemic and non-anemic primigravidae, including several lipid metabolism proteins and molecular transport proteins involved in the acute phase response signaling network. These differences were not observed in multigravid women who enjoy specific immunity that protect them from PM. In a confirmatory study of a larger cohort of primigravid women, levels of the lipid metabolism protein Apolipoprotein (Apo)-AI were significantly lower in PM+ women with SA.

Conclusions

Apo-AI levels are significantly lower in severely anemic primigravidae with PM, and ApoA1 levels positively correlate with hemoglobin levels in primigravid but not multigravid women. Apo-AI is known to have anti-inflammatory effects, and thus Apo-AI reductions may contribute to the inflammatory processes that result in SA.

Direct cell-cell contact between periodontal ligament fibroblasts and osteoclast precursors synergistically increases the expression of genes related to osteoclastogenesis

The formation of bone resorbing osteoclasts in vivo is orchestrated by cells of the osteoblast lineage such as periodontal ligament fibroblasts that provide the proper signals to osteoclast precursors. Although the requirement of cell-cell interactions is widely acknowledged, it is unknown whether these interactions influence the expression of genes required for osteoclastogenesis and the ultimate formation of osteoclasts. In the present study we investigated the effect of cell-cell interaction on the mRNA expression of adhesion molecules and molecules involved in osteoclast formation in cultures of peripheral blood mononuclear cells (PBMCs) and human primary periodontal ligament fibroblasts, both as solitary cultures and in co-culture. We further analyzed the formation of multinucleated, tartrate resistant acid phosphatase (TRACP) positive cells and assessed their bone resorbing abilities. Interestingly, gene expression of intercellular adhesion molecule-1 (ICAM-1) and of osteoclastogenesis-related genes (RANKL, RANK, TNF-alpha, and IL-1beta) was highly up-regulated in the co-cultures compared to mono-cultures and the 5-10-fold up-regulation reflected a synergistic increase due to direct cell-cell interaction. This induction strongly overpowered the effects of known osteoclastogenesis inducers 1,25(OH)(2)VitD(3) and dexamethasone. In case of indirect cell-cell contact mRNA expression was not altered, indicating that heterotypic adhesion is required for the increase in gene expression. In addition, the number of osteoclast-like cells that were formed in co-culture with periodontal ligament fibroblasts was significantly augmented compared to mono-cultures. Our data indicate that cell-cell adhesion between osteoclast precursors and periodontal ligament fibroblasts significantly modulates the cellular response which favors the expression of osteoclast differentiation genes and the ultimate formation of osteoclasts.

Stratification and monitoring of juvenile idiopathic arthritis patients by synovial proteome analysis

Juvenile idiopathic arthritis (JIA) comprises a poorly understood group of chronic, childhood onset, autoimmune diseases with variable clinical outcomes. We investigated whether profiling of the synovial fluid (SF) proteome by a fluorescent dye based, two-dimensional gel (DIGE) approach could distinguish patients in whom inflammation extends to affect a large number of joints, early in the disease process. SF samples from 22 JIA patients were analyzed: 10 with oligoarticular arthritis, 5 extended oligoarticular and 7 polyarticular disease. SF samples were labeled with Cy dyes and separated by two-dimensional electrophoresis. Multivariate analyses were used to isolate a panel of proteins which distinguish patient subgroups. Proteins were identified using MALDI-TOF mass spectrometry with expression further verified by Western immunoblotting and immunohistochemistry. Hierarchical clustering based on the expression levels of a set of 40 proteins segregated the extended oligoarticular from the oligoarticular patients (p < 0.05). Expression patterns of the isolated protein panel have also been observed over time, as disease spreads to multiple joints. The data indicates that synovial fluid proteome profiles could be used to stratify patients based on risk of disease extension. These protein profiles may also assist in monitoring therapeutic responses over time and help predict joint damage.

Liver X receptor agonism promotes articular inflammation in murine collagen-induced arthritis

OBJECTIVE

Liver X receptors (LXRs) have previously been implicated in the regulation of inflammation and have, in general, been ascribed an antiinflammatory role. This study was therefore undertaken to explore the biologic mechanisms of LXRs in vivo and in vitro in an experimental inflammatory arthritis model.

METHODS

Male DBA/1 mice were immunized with type II collagen and treated from an early or established stage of arthritis with 2 different concentrations of the LXR agonists T1317 and GW3965 or vehicle control. The mice were monitored for articular inflammation and cartilage degradation by scoring for clinical signs of arthritis, histologic examination of the joints, and analysis of serum cytokine and antibody levels. In vitro, primary human monocytes and T cells were cultured in the presence of GW3965 or T1317, and the concentrations of proinflammatory cytokines were measured by multiplex assay.

RESULTS

Contrary to expectations, LXR agonism with the use of 2 discrete, specific molecular entities led to substantial exacerbation of articular inflammation and cartilage destruction in this murine collagen-induced arthritis model. This was associated ex vivo with elevated cytokine expression, with enhanced Th1 and Th17 cellular responses, and with elevated collagen-specific autoantibody production. In vitro, LXR agonists, in concert with lipopolysaccharide, promoted cytokine and chemokine release from human monocytes, and similar effects were observed in a T cell-macrophage coculture model that closely recapitulates the pathways that drive synovial cytokine release.

CONCLUSION

Since LXRs are present in rheumatoid arthritis (RA) synovium, these results suggest that LXR-mediated pathways could exacerbate the chronic inflammatory response typical of RA.

Developments in the scientific understanding of rheumatoid arthritis

Rheumatoid arthritis (RA) is recognized to be an autoimmune disease that causes preclinical systemic abnormalities and eventually leads to synovial inflammation and destruction of the joint architecture. Recently identified genetic risk factors and novel insights from animal models of spontaneous arthritis have lent support to the concept that thymic selection of an autoreactive T-cell repertoire is an important risk factor for this disease. With advancing age, defects in the homeostatic control of the T-cell pool and in the setting of signaling thresholds lead to the accumulation of pro-inflammatory T-effector cell populations and loss of tolerance to neo-antigens, such as citrullinated peptides. As the breakdown of tolerance to modified self-antigens can precede synovitis by decades, repair of homeostatic defects may open a unique window of opportunity for preventive interventions in RA. The end result of RA, destruction of cartilage and bone, appears to be driven by cytokine- and cell contact-induced activation of synoviocytes and monocytic cells, some of which differentiate into tissue-destructive osteoclasts. Targeting mediators involved in this process has greatly improved the management of this chronic inflammatory syndrome.

Comparative analysis of synovial fluid and plasma proteomes in juvenile arthritis--proteomic patterns of joint inflammation in early stage disease

Synovial fluid is a potential source of novel biomarkers for many arthritic disorders involving joint inflammation, including juvenile idiopathic arthritis. We first compared the distinctive protein 'fingerprints' of local inflammation in synovial fluid with systemic profiles within matched plasma samples. The synovial fluid proteome at the time of joint inflammation was then evaluated across clinical subgroups to identify early disease associated proteins. We measured the synovial fluid and plasma proteomes using the two-dimensional fluorescence difference gel electrophoresis approach. Image analysis software was used to highlight the expression levels of joint and subgroup associated proteins across the study cohort (n = 32). A defined subset of 30 proteins had statistically significant differences (p < 0.05) between sample types such that synovial fluid could be differentiated from plasma. Furthermore distinctive synovial proteome expression patterns segregate patient subgroups. Protein expression patterns localized in the chronically inflamed joint therefore have the potential to identify patients more likely to suffer disease which will spread from a single joint to multiple joints. The proteins identified could act as criteria to prevent disease extension by more aggressive therapeutic intervention directed at an earlier stage than is currently possible.

T cells dampen innate immune responses through inhibition of NLRP1 and NLRP3 inflammasomes

Inflammation is a protective attempt by the host to remove injurious stimuli and initiate the tissue healing process. The inflammatory response must be actively terminated, however, because failure to do so can result in 'bystander' damage to tissues and diseases such as arthritis or type-2 diabetes. Yet the mechanisms controlling excessive inflammatory responses are still poorly understood. Here we show that mouse effector and memory CD4(+) T cells abolish macrophage inflammasome-mediated caspase-1 activation and subsequent interleukin 1beta release in a cognate manner. Inflammasome inhibition is observed for all tested NLRP1 (commonly called NALP1) and NLRP3 (NALP3 or cryopyrin) activators, whereas NLRC4 (IPAF) inflammasome function and release of other inflammatory mediators such as CXCL2, interleukin 6 and tumour necrosis factor are not affected. Suppression of the NLRP3 inflammasome requires cell-to-cell contact and can be mimicked by macrophage stimulation with selected ligands of the tumour necrosis factor family, such as CD40L (also known as CD40LG). In a NLRP3-dependent peritonitis model, effector CD4(+) T cells are responsible for decreasing neutrophil recruitment in an antigen-dependent manner. Our findings reveal an unexpected mechanism of inflammasome inhibition, whereby effector and memory T cells suppress potentially damaging inflammation, yet leave the primary inflammatory response, crucial for the onset of immunity, intact.

In vivo activated monocytes from the site of inflammation in humans specifically promote Th17 responses

Th17 cells are a recently defined subset of proinflammatory T cells that contribute to pathogen clearance and tissue inflammation by means of the production of their signature cytokine IL-17A (henceforth termed IL-17). Although the in vitro requirements for human Th17 development are reasonably well established, it is less clear what their in vivo requirements are. Here, we show that the production of IL-17 by human Th17 cells critically depends on both the activation status and the anatomical location of accessory cells. In vivo activated CD14+ monocytes were derived from the inflamed joints of patients with active rheumatoid arthritis (RA). These cells were found to spontaneously and specifically promote Th17, but not Th1 or Th2 responses, compared with resting CD14+ monocytes from the blood. Surprisingly, unlike Th17 stimulation by monocytes that were in vitro activated with lipopolysaccharide, intracellular IL-17 expression was induced by in vivo activated monocytes in a TNF-alpha- and IL-1beta-independent fashion. No role for IL-6 or IL-23 production by either in vitro or in vivo activated monocytes was found. Instead, in vivo activated monocytes promoted Th17 responses in a cell-contact dependent manner. We propose that, in humans, newly recruited memory CD4(+) T cells can be induced to produce IL-17 in nonlymphoid inflamed tissue after cell-cell interactions with activated monocytes. Our data also suggest that different pathways may be utilized for the generation of Th17 responses in situ depending on the site or route of accessory cell activation.

Effect of N-acetyl-L-cysteine on Cytokine Production by Human Peripheral Blood Mononuclear Cells

OBJECTIVES

This study investigates the in vitro effect of the antioxidant drug, N-acetyl-L-cysteine (NAC), on cytokine production by peripheral blood mononuclear cells (PBMC).

METHODS

PBMC were isolated by Ficoll-Hypaque, and stimulated with anti-CD3 antibodies, phytohaemagglutinin (PHA), lipopolysaccharide (LPS) for 24 hours in the presence or absence of 5 mM NAC. The cytokines produced were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Treatment with NAC significantly up-regulates the secretion of IL-1β, IL-5 (interleukin) and IFN-γ (interferon) and down regulates IL-10 production, after anti-CD3 or PHA (p<0.05), but not after LPS stimulation. NAC also significantly increased total IL-12 secretion after anti-CD3 (but not PHA or LPS) stimulation and IL-12p40 after anti-CD3, PHA, and LPS stimulation (p <0.05).

CONCLUSION

These results indicate that NAC up-regulated the production of pro-inflammatory cytokines, and down regulated anti-inflammatory cytokine production by PBMC, in a process which may be associated with increased levels of glutathione (GSH). Further work is required to determine whether this increase or decrease in cytokine production is due to direct effect of NAC.

Glatiramer acetate increases IL-1 receptor antagonist but decreases T cell-induced IL-1beta in human monocytes and multiple sclerosis

Mechanisms of action as well as cellular targets of glatiramer acetate (GA) in multiple sclerosis (MS) are still not entirely understood. IL-1beta is present in CNS-infiltrating macrophages and microglial cells and is an important mediator of inflammation in experimental autoimmune encephalitis (EAE), the MS animal model. A natural inhibitor of IL-1beta, the secreted form of IL-1 receptor antagonist (sIL-1Ra) improves EAE disease course. In this study we examined the effects of GA on the IL-1 system. In vivo, GA treatment enhanced sIL-1Ra blood levels in both EAE mice and patients with MS, whereas IL-1beta levels remained undetectable. In vitro, GA per se induced the transcription and production of sIL-1Ra in isolated human monocytes. Furthermore, in T cell contact-activated monocytes, a mechanism relevant to chronic inflammation, GA strongly diminished the expression of IL-1beta and enhanced that of sIL-1Ra. This contrasts with the effect of GA in monocytes activated upon acute inflammatory conditions. Indeed, in LPS-activated monocytes, IL-1beta and sIL-1Ra production were increased in the presence of GA. These results demonstrate that, in chronic inflammatory conditions, GA enhances circulating sIL-1Ra levels and directly affects monocytes by triggering a bias toward a less inflammatory profile, increasing sIL-1Ra while diminishing IL-1beta production. This study sheds light on a mechanism that is likely to participate in the therapeutic effects of GA in MS.

Lymphocyte/macrophage interactions: biomaterial surface-dependent cytokine, chemokine, and matrix protein production

The role of lymphocytes in the biological response to synthetic polymers is poorly understood despite the transient appearance of lymphocytes at the biomaterial implant site. To investigate cytokines, chemokines, and extracellular matrix (ECM) proteins produced by lymphocytes and macrophages in response to biomaterial surfaces, human peripheral blood monocytes and lymphocytes were co-cultured on polyethylene terephthalate (PET)-based material surfaces displaying distinct hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic chemistries. Antibody array screening showed the majority of detected proteins are inflammatory mediators that guide the early inflammatory phases of wound healing. Proteomic ELISA quantification and adherent cell analysis were performed after 3, 7, and 10 days of culture. IL-2 and IFN-gamma were not detected in any co-cultures suggesting lack of lymphocyte activation. The hydrophilic/neutral surfaces increased IL-8 relative to the hydrophobic PET surface (p < 0.05). The hydrophilic/anionic surfaces promoted increased TNF-alpha over hydrophobic and cationic surfaces and increased MIP-1beta compared to hydrophobic surfaces (p < 0.05). Since enhanced macrophage fusion was observed on hydrophilic/anionic surfaces, the production of these cytokines likely plays an important role in the fusion process. The hydrophilic/cationic surface promoted IL-10 production and increased matrix metalloproteinase (MMP)-9/tissue inhibitor of MMP (TIMP) relative to hydrophilic/neutral and anionic surfaces (p < 0.05). These results suggest hydrophilic/neutral and anionic surfaces promote pro-inflammatory responses and reduced degradation of the ECM, whereas the hydrophilic/cationic surfaces induce an anti-inflammatory response and greater MMP-9/TIMP with an enhanced potential for ECM breakdown. The study also underscores the usefulness of protein arrays in assessing the role of soluble mediators in the inflammatory response to biomaterials.

Autoantibodies to myelin basic protein (MBP) in healthy individuals and in patients with multiple sclerosis: a role in regulating cytokine responses to MBP

Anti-myelin basic protein (-MBP) autoantibodies have generally been considered to be absent from sera from healthy individuals, but to be detectable in sera from some patients with multiple sclerosis (MS). However, their pathogenic role is uncertain. We demonstrate the presence of MBP-reactive autoantibodies in sera from 17 healthy individuals and 17 MS patients. The addition of MBP to the sera caused a dose-dependent deposition of MBP and co-deposition of immunoglobulin M (IgM) and fragments of complement component 3 (C3) on allogeneic monocytes. Calcium chelation abrogated the immunoglobulin deposition, indicating that formation of complement-activating immune complexes played a role in the binding process. Furthermore, MBP elicited tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 production by normal mononuclear cells in the presence of serum from both patients and controls. Mononuclear cells from MS patients responded to MBP with the production of interferon (IFN)-gamma, IL-4 and IL-5, in addition to TNF-alpha and IL-10. The production of IFN-gamma and IL-5 was increased when MS serum was added rather than normal serum. Denaturation of MBP strongly inhibited MBP deposition and the MBP-induced IgM deposition and cytokine production, indicating that these events were facilitated by autoantibodies recognizing conformational epitopes on MBP. We infer that MBP-elicited TNF-alpha and IL-10 responses are promoted to equal extents by naturally occurring MBP autoantibodies and autoantibodies contained in MS sera. However, the latter seem to be more efficient in facilitating the production of IFN-gamma and IL-5.

T cells in rheumatoid arthritis

Over the past decade and a half, advances in our understanding of the pathogenesis of immune-mediated diseases such as rheumatoid arthritis (RA) have translated directly into benefit for patients. Much of this benefit has arisen through the introduction of targeted biological therapies. At the same time, technological advances have made it possible to define, at the cellular and molecular levels, the key pathways that influence the initiation and persistence of chronic inflammatory autoimmune reactions. As our understanding grows, it is likely that this knowledge will be translated into a second generation of biological therapies that are tailor-made for the patient. This review summarizes current perspectives on RA disease pathogenesis, with particular emphasis on what RA T cells look like, what they are likely to see, and how they contribute to persistence of the chronic inflammatory response.

Co-stimulatory modulation in rheumatoid arthritis: the role of (CTLA4-Ig) abatacept

Associations between rheumatoid arthritis (RA) susceptibility and polymorphism in multiple immunoregulatory genes suggest a role of altered T cell function in the disease. The growing relevance of the oxidative stress in RA synovitis, which results in a number of T cell signalling abnormalities, is reinforced by the demonstration of a direct NO inducing activity through the shared epitope of the HLA class II molecules HLA-DRbeta1, with secondary lymphocytes oxidative damage. Direct T cell/macrophage contact-dependent activation, one of the driving mechanisms of synovitis, is mediated by co-stimulatory molecules as well as cell membrane cytokines and may also result in an impaired suppressive function of T regulatory cells (Treg) in RA joints. The fusion of CTLA4 extracellular binding domain to the Fcgamma1 allows to obtain a soluble CTLA4 receptor, the dimeric recombinant human fusion protein abatacept (CTLA4-Ig). The improved knowledge of the CTLA4-B7 co-stimulation regulatory mechanisms by signals delivered into DCs and Tregs provides multiple potential targets for the abatacept treatment. CTLA4-Ig shows the capacity, either ex vivo or in vivo, to interrupt at multiple steps the ongoing inflammatory and destructive process, and to concur in restoring the immunoregulatory balance in RA.

T helper cell type 1 (Th1), Th2 and Th17 responses to myelin basic protein and disease activity in multiple sclerosis

Autoreactive T cells are thought to play an essential role in the pathogenesis of multiple sclerosis (MS). We examined the stimulatory effect of human myelin basic protein (MBP) on mononuclear cell (MNC) cultures from 22 patients with MS and 22 sex-matched and age-matched healthy individuals, and related the patient responses to disease activity, as indicated by magnetic resonance imaging. The MBP induced a dose-dependent release of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) by patient-derived MNCs. The patients' cells produced higher amounts of IFN-gamma and TNF-alpha, and lower amounts of IL-10, than cells from healthy controls (P<0.03 to P<0.04). Five patients with MS and no controls, displayed MBP-induced CD4+ T-cell proliferation. These high-responders exhibited enhanced production of IL-17, IFN-gamma, IL-5 and IL-4 upon challenge with MBP, as compared with the remaining patients and the healthy controls (P<0.002 to P<0.01). A strong correlation was found between the MBP-induced CD4+ T-cell proliferation and production of IL-17, IFN-gamma, IL-5 and IL-4 (P<0.0001 to P<0.01) within the patient group, and the production of IL-17 and IL-5 correlated with the number of active plaques on magnetic resonance images (P=0.04 and P=0.007). These data suggest that autoantigen-driven CD4+ T-cell proliferation and release of IL-17 and IL-5 may be associated with disease activity. Larger studies are needed to confirm this.

Resting CD4+ effector memory T cells are precursors of bystander-activated effectors: a surrogate model of rheumatoid arthritis synovial T-cell function

Background

Previously we described a system whereby human peripheral blood T cells stimulated for 8 days in a cytokine cocktail acquired effector function for contact-dependent induction of proinflammatory cytokines from monocytes. We termed these cells cytokine-activated (Tck) cells and found that the signalling pathways elicited in the responding monocytes were identical whether they were placed in contact with Tck cells or with T cells isolated from rheumatoid arthritis (RA) synovial tissue.

Methods

Here, using magnetic beads and fluorescence-activated cell sorting, we extensively phenotype the Tck effector cells and conclude that effector function resides within the CD4⁺CD45RO⁺, CCR7^-, CD49d^high population, and that these cells are derived from the effector memory CD4⁺ T cells in resting blood.

Results

After stimulation in culture, these cells produce a wide range of T-cell cytokines, undergo proliferation and differentiate to acquire an extensively activated phenotype resembling RA synovial T cells. Blocking antibodies against CD69, CD18, or CD49d resulted in a reduction of tumour necrosis factor-α production from monocytes stimulated with CD4⁺CD45RO⁺ Tck cells in the co-culture assay. Moreover, blockade of these ligands also resulted in inhibition of spontaneous tumour necrosis factor-α production in RA synovial mononuclear cell cultures.

Conclusion

Taken together, these data strengthen our understanding of T-cell effector function, highlight the multiple involvement of different cell surface ligands in cell-cell contact and, provide novel insights into the pathogenesis of inflammatory RA disease.

Reduced arthritis in MIF deficient mice is associated with reduced T cell activation: down-regulation of ERK MAP kinase phosphorylation

Macrophage migration inhibitory factor (MIF) is a pleiotropic pro-inflammatory cytokine with many cellular targets in rheumatoid arthritis (RA). MIF has been reported to activate cells via mitogen-activated protein kinase and serine/threonine kinase (AKT or protein kinase B)-dependent signal transduction pathways. Its contribution to T cell activation and signalling in RA is not known. Using MIF -/- mice and a T cell-mediated model of RA, antigen-induced arthritis, we investigated the role of MIF in T cell activation and signalling. Arthritis severity was significantly reduced in MIF -/- mice compared with wildtype mice. This reduction was associated with decreased T cell activation parameters including footpad delayed type hypersensitivity, antigen-induced splenocyte proliferation and cytokine production. Splenocyte proliferation required extracellular signal-regulated kinase (ERK)1/2 phosphorylation, and decreased T cell activation in MIF -/- mice was associated with decreased phosphorylation of ERK1/2 but not AKT. Collectively, these data suggest that MIF promotes antigen-specific immune responses via regulation of ERK phosphorylation in T cells.

MHC class I chain-related molecules induced on monocytes by IFN-gamma promote NK cell activation

NKG2D receptor-ligand interaction triggers NK cell-mediated cytolysis and IFN-gamma secretion. IFN-gamma produced by NK cells has been found to promote the interaction between NK cells and monocytes; however, the underlying mechanism remains elusive. We demonstrate here that IFN-gamma exclusively induced or upregulated the expression of MHC class I chain-related (MIC) molecules, which are ligands of the NKG2D receptor, on the surface of human monocytes of the PBMC population. The IFN-gamma-induced MIC molecules on monocytes played an essential role in triggering the activation of NK cells because mAb-mediated masking of the MIC molecules and the inhibition of cell-to-cell contact using transwell inserts significantly abolished NK cell activation. Meanwhile, membrane-bound IL-15 (mIL-15) was concomitantly induced with MIC molecules on IFN-gamma-treated monocytes and played an essential role in protecting NK cells cocultured with monocytes from MIC-induced NKG2D down-modulation. Therefore, we conclude that the IFN-gamma-induced MIC molecules participated in monocyte/NK cell interaction and that this interaction also involved mIL-15.