Activation of Invariant NKT cells with glycolipid ligand α-galactosylceramide ameliorates glucose-6-phosphate isomerase peptide-induced arthritis

Berberine: A natural modulator of immune cells in multiple sclerosis

Berberine is a benzylisoquinoline alkaloid found in such plants as Berberis vulgaris, Berberis aristata, and others, revealing a variety of pharmacological properties as a result of interacting with different cellular and molecular targets. Recent studies have shown the immunomodulatory effects of Berberine which result from its impacts on immune cells and immune response mediators such as diverse T lymphocyte subsets, dendritic cells (DCs), and different inflammatory cytokines. Multiple sclerosis (MS) is a chronic disabling and neurodegenerative disease of the central nervous system (CNS) characterized by the recruitment of autoreactive T cells into the CNS causing demyelination, axonal damage, and oligodendrocyte loss. There have been considerable changes discovered in MS regards to the function and frequency of T cell subsets such as Th1 cells, Th17 cells, Th2 cells, Treg cells, and DCs. In the current research, we reviewed the outcomes of in vitro, experimental, and clinical investigations concerning the modulatory effects that Berberine provides on the function and numbers of T cell subsets and DCs, as well as important cytokines that are involved in MS.

Cell-Specific Gene Networks and Drivers in Rheumatoid Arthritis Synovial Tissues

Rheumatoid arthritis (RA) is a common autoimmune and inflammatory disease characterized by inflammation and hyperplasia of the synovial tissues. RA pathogenesis involves multiple cell types, genes, transcription factors (TFs) and networks. Yet, little is known about the TFs, and key drivers and networks regulating cell function and disease at the synovial tissue level, which is the site of disease. In the present study, we used available RNA-seq databases generated from synovial tissues and developed a novel approach to elucidate cell type-specific regulatory networks on synovial tissue genes in RA. We leverage established computational methodologies to infer sample-specific gene regulatory networks and applied statistical methods to compare network properties across phenotypic groups (RA versus osteoarthritis). We developed computational approaches to rank TFs based on their contribution to the observed phenotypic differences between RA and controls across different cell types. We identified 18,16,19,11 key regulators of fibroblast-like synoviocyte (FLS), T cells, B cells, and monocyte signatures and networks, respectively, in RA synovial tissues. Interestingly, FLS and B cells were driven by multiple independent co-regulatory TF clusters that included MITF, HLX, BACH1 (FLS) and KLF13, FOSB, FOSL1 (synovial B cells). However, monocytes were collectively governed by a single cluster of TF drivers, responsible for the main phenotypic differences between RA and controls, which included RFX5, IRF9, CREB5. Among several cell subset and pathway changes, we also detected reduced presence of NKT cell and eosinophils in RA synovial tissues. Overall, our novel approach identified new and previously unsuspected KDG, TF and networks and should help better understanding individual cell regulation and co-regulatory networks in RA pathogenesis, as well as potentially generate new targets for treatment.

Exploring the chondroprotective effect of Chaenomeles speciosa on Glucose-6-Phosphate Isomerase model mice using an integrated approach of network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) has been used in China for a long time and is gradually gaining more and more recognition worldwide. Chaenomeles speciosa (CSP) (Chinese Pinyin: mugua) is a medicinal and food herb that has long been used as a folk medicine for rheumatic diseases, yet its bioactive components and therapeutic mechanisms are not clear.

AIM OF THE STUDY

Exploring anti-inflammatory and chondroprotective effects of CSP on rheumatoid arthritis (RA) and its possible targets of action.

MATERIALS AND METHODS

In this study, we performed an integrated approach of network pharmacology, molecular docking and experimental studies to explore the potential mechanism of action of CSP in the treatment of cartilage damage in RA.

RESULTS

Studies have shown that Quercetin, ent-Epicatechin and Mairin may be the main active compounds of CSP in the treatment of RA, while AKT1, VEGFA, IL-1β, IL-6, MMP9 etc. are considered as core target proteins to which the main active compounds in CSP bind, as further confirmed by molecular docking. In addition, the potential molecular mechanism of CSP for the treatment of cartilage damage in RA predicted by network pharmacology analysis was validated by in vivo experiments. CSP was found to downregulate the expression of AKT1, VEGFA, IL-1β, IL-6, MMP9, ICAM1, VCAM1, MMP3, MMP13 and TNF-α and increase the expression of COL-2 in the joint tissue of Glucose-6-Phosphate Isomerase (G6PI) model mice. Thus CSP contributes to the treatment of rheumatoid arthritis cartilage destruction.

CONCLUSION

This study showed that CSP has multi-component, multi-target and multi-pathway characteristics in treating cartilage damage in RA, which can achieve the effect of treating RA by inhibiting the expression of inflammatory factors, reducing neovascularization and alleviating the damage to cartilage caused by the diffusion of synovial vascular opacities, and reducing the degradation of cartilage by MMPs to play a protective role in RA cartilage damage. In conclusion, this study indicates that CSP is a candidate Chinese medicine for further research in treating cartilage damage in RA.

Migration, Distribution, and Safety Evaluation of Specific Phenotypic and Functional Mouse Spleen-Derived Invariant Natural Killer T2 Cells after Adoptive Infusion

Herein, the migration distribution and safety of specific phenotypic and functionally identified spleen-derived invariant natural killer T2 (iNKT2) cells after adoptive infusion in mice were studied. The proliferation and differentiation of iNKT cells were induced by intraperitoneal injection of α-galactosylceramide (α-GalCer) in vivo. Mouse spleens were isolated in a sterile environment. iNKT cells were isolated by magnetic-activated cell sorting columns (MS columns). Cytometric bead array (CBA) assay was used to detect cytokine secretion in the supernatant stimulated by iNKT cells. The basic life status of the mice was observed, and systematic quantitative scoring was conducted after injecting spleen-derived iNKT cells through the tail vein. An in vivo imaging system was used to trace the migration and distribution of iNKT cells in DBA mice. The percentage of the iNKT2 subgroup was the highest in 3 days after intraperitoneal injection of α-GalCer, and iNKT2 subsets accounted for more than 92% after separation and purification by magnetic-activated cell sorting (MACS). Anti-inflammatory cytokine IL-4 was mainly found in the supernatant of cell cultures. The adoptive infusion of iNKT cells into healthy mice resulted in no significant change in the basic life status of mice compared with the noninjected group. iNKT cells were detected in the lung, spleen, and liver, but no fluorescence was detected in lymph nodes and thymus. After dissecting the mice, it was found that there were no significant abnormalities in the relevant immune organs, brain, heart, kidney, lung, and other organs. Intraperitoneal injection of α-GalCer results in a large number of iNKT2 cells, mainly secreting anti-inflammatory cytokine IL-4, from the spleen of mice. After adoptive infusion, the iNKT2 cells mainly settled in the liver and spleen of mice with a satisfactory safety profile.

Molecular Aspects and Future Perspectives of Cytokine-Based Anti-cancer Immunotherapy

Cytokine-based immunotherapy is a promising field in the cancer treatment, since cytokines, as proteins of the immune system, are able to modulate the host immune response toward cancer cell, as well as directly induce tumor cell death. Since a low dose monotherapy with some cytokines has no significant therapeutic results and a high dose treatment leads to a number of side effects caused by the pleiotropic effect of cytokines, the problem of understanding the influence of cytokines on the immune cells involved in the pro- and anti-tumor immune response remains a pressing one. Immune system cells carry CD makers on their surface which can be used to identify various populations of cells of the immune system that play different roles in pro- and anti-tumor immune responses. This review discusses the functions and specific CD markers of various immune cell populations which are reported to participate in the regulation of the immune response against the tumor. The results of research studies and clinical trials investigating the effect of cytokine therapy on the regulation of immune cell populations and their surface markers are also discussed. Current trends in the development of cancer immunotherapy, as well as the role of cytokines in combination with other therapeutic agents, are also discussed.

Subcutaneous administration of α-GalCer activates iNKT10 cells to promote M2 macrophage polarization and ameliorates chronic inflammation of obese adipose tissue

OBJECTIVE

The role of iNKT cells was investigated in chronic adipose tissue inflammation in obese mice after administration of α-GalCer in different pathways.

METHODS

C57BL/6J mice were fed high-fat diet (HFD) for 12 weeks to establish the obese mouse model. The pathology of adipose tissue was observed by H&E staining. The rates of iNKT cells, macrophages and cell subsets in adipose tissue were detected by FCM. Cytokine levels in serum and adipose tissue lymphocyte-stimulated supernatants were assessed with the CBA kit. The expression levels of related transcription factor in adipose tissue were detected by Western blot.

RESULTS

The proportions of iNKT cells, iNKT10 cells and M2 macrophages were decreased, while those of iNKT1 and M1 macrophages were increased in adipose tissue of HFD-fed mice. The expression levels of the related transcriptional proteins E4BP4 and Arg-1 were decreased while iNOS expression was increased in adipose tissue. Administration of α-GalCer by subcutaneous injection resulted in increased rates of iNKT10 cells and M2 macrophages, and decreased amounts of M1 macrophages in adipose tissue of HFD-fed mice. The expression of E4BP4 and Arg-1 were up-regulated, but iNOS was down-regulated. Meanwhile, infiltration of inflammatory cells into adipose tissue was further reduced.

CONCLUSION

The imbalance between the proportions of iNKT1 and iNKT10 cells may be involved in the development of chronic inflammation in obese adipose tissue. Administration of α-GalCer by subcutaneous injection in HFD-fed mice activates adipose tissue iNKT10 cells, which promote M2 macrophage polarization and improve chronic inflammation in obese adipose tissue.

Revisit of autoimmunity to glucose-6-phosphate isomerase in experimental and rheumatoid arthritis

Rheumatoid arthritis (RA) is an inflammatory disorder characterized by synovial inflammation in multiple joints. Autoantibodies (Abs) are the hallmark of RA, and as disease-specific and diagnostic markers, rheumatoid factor and anti-citrullinated protein antibody (ACPA) are produced pre-clinically, but their pathogenic roles in RA remain elusive. In this review, we focus on one of the candidate autoantigens in RA; glucose-6-phosphate isomerase (GPI). The arthritogenic role of GPI has been confirmed in two different mouse models: the K/BxN- and GPI-induced arthritis models. Both anti-GPI Abs and citrullinated-GPI peptide Abs have been detected in human RA. Studies conducted in these rodent models have confirmed that the pathogenesis of arthritis involves the localization of autoantigens not only in the joints but also in the circulation. In this review, we revisit and summarize the arthritogenic relevance of GPI in animal RA models and in human RA, and extend the discussion to joint-specific inflammation.

Methylation of H3K27 and H3K4 in key gene promoter regions of thymus in RA mice is involved in the abnormal development and differentiation of iNKT cells

Epigenetic modifications have been shown to be important for immune cell differentiation by regulating gene transcription. However, the role and mechanism of histone methylation in the development and differentiation of iNKT cells in rheumatoid arthritis (RA) mice have yet to be deciphered. The DBA/1 mouse RA model was established by using a modified GPI mixed peptide. We demonstrated that total peripheral blood, thymus, and spleen iNKT cells in RA mice decreased significantly, while iNKT1 in the thymus and spleen was increased significantly. PLZF protein and PLZF mRNA levels were significantly decreased in thymus DP T cells, while T-bet protein and mRNA were significantly increased in thymus iNKT cells. We found a marked accumulation in H3K27me3 around the promoter regions of the signature gene Zbtb16 in RA mice thymus DP T cells, and an accumulation of H3K4me3 around the promoters of the Tbx21 gene in iNKT cells. The expression levels of UTX in the thymus of RA mice were significantly reduced. The changes in the above indicators were particularly significant in the progressive phase of inflammation (11 days after modeling) and the peak phase of inflammation (14 days after modeling) in RA mice. Developmental and differentiation defects of iNKT cells in RA mice were associated with abnormal methylation levels (H3K27me3 and H3K4me3) in the promoters of key genes Zbtb16 (encoding PLZF) and Tbx21 (encoding T-bet). Decreased UTX of thymus histone demethylase levels resulted in the accumulation of H3K27me3 modification.

Activation of hepatic iNKT2 cells by α-GalCer ameliorates hepatic steatosis induced by high-fat diet in C57BL/6J mice

The existence of association between the subpopulation of iNKT cells with different functions and nonalcoholic fatty liver disease has not been confirmed. To investigative the role of iNKT cells in the pathogenesis of nonalcoholic fatty liver disease, we established a non-alcoholic fatty liver model by feeding C57BL/6J mice for 12 weeks with a high-fat diet and injecting α-GalCer through different routes to activate hepatic iNKT cells. The liver of the mice fed a high-fat diet (HFD) had severe hepatic steatosis appearance, elevated pro-inflammatory cytokines and reduced anti-inflammatory cytokines in the liver, and high serum levels of TC, LDL, HDL, and ALT. Our results showed that the percentage of iNKT cells in the liver of the HFD-fed mice was lower than that of the control mice. The expression levels of the related transcription factor of T-bet increased but that of GATA-3 decreased in the HFD-fed mice. The administration of α-GalCer by intraperitoneal injection resulted in increasing of hepatic iNKT and iNKT2 cells but decreasing of hepatic iNKT1 cells, and the expression of GATA-3 and anti-inflammatory cytokine (IL-4) was increased in the liver, and hepatic steatosis was ameliorated in the HFD-fed mice. The administration of α-GalCer by subcutaneous injection resulted in a decrease in hepatic iNKT and iNKT2 and an augmentation of hepatic iNKT1 cells. However, hepatic steatosis was not significantly improved. We concluded that the intraperitoneal injection with α-GalCer effectively improved hepatic steatosis, according to increasing the number of hepatic iNKT2 cells. The precise mechanism requires further exploration.

Immunoporosis: A New Role for Invariant Natural Killer T (NKT) Cells Through Overexpression of Nuclear Factor-κB Ligand (RANKL)

Background

Osteoporosis affects millions of postmenopausal women worldwide. Invariant natural killer T cells (iNKT) are important cells for bone homeostasis. The sim of this study was to investigate the contribution of invariant natural killer T cells (iNKT) in the increased receptor activator of the nuclear factor-κB ligand (RANKL) pool and bone resorption, a characteristic of patients with osteoporosis.

Material/Methods

Whole blood was collected from 79 female patients. The dual energy x-absorptiometry scan was performed in all patients, and the T-score was calculated in order to classify our patients according to the World Human Organization (WHO) criteria for diagnosis and classification of osteoporosis. Eleven patients had a T-score <−1.0 and were encompassed in our normal donors (ND) group, 46 patients had a T-score between −1 and −2.5 and were included in the osteopenia group, while 22 patients had a T-score > −2.5 and were included in the osteoporosis group. We performed a-galactosylceramide activation of iNKT cells in vitro. Surface RANKL expression was detected by multicolor flow cytometry in naive and activated lymphocytes. Beta-Crosslaps (β-CTx) levels were measured in whole blood plasma by ELISA (enzyme-linked immunosorbent assay).

Results

Although iNKT cells were not clonally expanded in patients with osteoporosis, iNKT cells from osteoporotic patients overexpressed RANKL compared to ND and osteopenic patients. This is a distinctive feature of iNKT cells and is not seen in conventional T-lymphocytes. RANKL expression in iNKT cells was not related to β-CTx levels in the blood. Finally, iNKT cell activation by the prototypal glycolipid ligand α-galactosylceramide increased by 8 times their RANKL expression.

Conclusions

In patients with osteoporosis, iNKT cells specifically overexpress RANKL, a cytokine that regulates osteoclast activity. It seems that iNKT cells have a long-standing effect of on the bone physiology, which plays an important role in the bone loss of patients with osteoporosis.

Therapeutic Potential of Invariant Natural Killer T Cells in Autoimmunity

Tolerance against self-antigens is regulated by a variety of cell types with immunoregulatory properties, such as CD1d-restricted invariant natural killer T (iNKT) cells. In many experimental models of autoimmunity, iNKT cells promote self-tolerance and protect against autoimmunity. These findings are supported by studies with patients suffering from autoimmune diseases. Based on these studies, the therapeutic potential of iNKT cells in autoimmunity has been explored. Many of these studies have been performed with the potent iNKT cell agonist KRN7000 or its structural variants. These findings have generated promising results in several autoimmune diseases, although mechanisms by which iNKT cells modulate autoimmunity remain incompletely understood. Here, we will review these preclinical studies and discuss the prospects for translating their findings to patients suffering from autoimmune diseases.

CD1d-dependent immune suppression mediated by regulatory B cells through modulations of iNKT cells

Regulatory B cells (Breg) express high levels of CD1d that presents lipid antigens to invariant natural killer T (iNKT) cells. The function of CD1d in Breg biology and iNKT cell activity during inflammation remains unclear. Here we show, using chimeric mice, cell depletion and adoptive cell transfer, that CD1d–lipid presentation by Bregs induces iNKT cells to secrete interferon (IFN)-γ to contribute, partially, to the downregulation of T helper (Th)1 and Th17-adaptive immune responses and ameliorate experimental arthritis. Mice lacking CD1d-expressing B cells develop exacerbated disease compared to wild-type mice, and fail to respond to treatment with the prototypical iNKT cell agonist α-galactosylceramide. The absence of lipid presentation by B cells alters iNKT cell activation with disruption of metabolism regulation and cytokine responses. Thus, we identify a mechanism by which Bregs restrain excessive inflammation via lipid presentation.

Regulatory B cells (Breg) are known to suppress immune responses by secreting interleukin-10 (IL-10). Here the authors show that, alternatively, Bregs may also present lipid antigens on surface CD1d to induce IFN-γ production from invariant natural killer cells to ameliorate experimental arthritis via IL-10-independent pathways.

What rheumatologists need to know about innate lymphocytes

Many rheumatic diseases are characterized by having an autoimmune background. Determining the mechanisms underlying autoimmunity is, therefore, important to further understand these diseases and to inform future lines of research aimed at developing new treatments and cures. As fast responders, innate lymphocytes have protective or pathogenic roles in the initiation as well as the maintenance of immune responses in general, and they contribute to tissue homeostasis, among other functions. Innate lymphocytes also seem to be involved in autoimmunity in particular. Since 2010, accumulating evidence clearly shows that different populations of innate lymphocytes have roles in responding to antigen-specific autoantibody and autoreactive T cells, thereby amplifying or attenuating disease processes. Cytotoxicity is a cardinal feature of many innate lymphocytes and can contribute to inflammatory tissue damage. Finally, innate lymphocytes can respond to biologic therapies for autoimmune diseases. Consequently, like TNF and other effector molecules, certain innate lymphocyte subsets might be appropriate therapeutic targets to ameliorate various autoimmune diseases. In this Review, we summarize the main characteristics and functions of innate lymphocyte subsets, and describe their roles in autoimmune disease. We also discuss how biologic therapies influence innate lymphocyte function and consider the potential for these cell subsets to act as future therapeutic targets.

Dysregulated osteoclastogenesis is related to natural killer T cell dysfunction in rheumatoid arthritis

OBJECTIVE

To investigate the role played by natural killer T (NKT) cells in osteoclastogenesis and their effects on inflammatory bone destruction.

METHODS

Patients with rheumatoid arthritis (RA) (n = 25) and healthy controls (n = 12) were enrolled in this study. In vitro osteoclastogenesis experiments were performed using peripheral blood mononuclear cells (PBMCs) in the presence of macrophage colony-stimulating factor and RANKL. PBMCs were cultured in vitro with α-galactosylceramide (αGalCer), and proliferation indices of NKT cells were estimated by flow cytometry. In vivo effects of αGalCer-stimulated NKT cells on inflammation and bone destruction were determined in mice with collagen-induced arthritis.

RESULTS

In vitro osteoclastogenesis was found to be significantly inhibited by αGalCer in healthy controls but not in RA patients. Proliferative responses of NKT cells and STAT-1 phosphorylation in monocytes in response to αGalCer were impaired in RA patients. Notably, αGalCer-stimulated NKT cells inhibited osteoclastogenesis mainly via interferon-γ production in a cytokine-dependent manner (not by cell-cell contact) and down-regulated osteoclast-associated genes. Mice treated with αGalCer showed less severe arthritis and reduced bone destruction. Moreover, proinflammatory cytokine expression in arthritic joints was found to be reduced by αGalCer treatment.

CONCLUSION

This study primarily demonstrates that αGalCer-stimulated NKT cells have a regulatory effect on osteoclastogenesis and a protective effect against inflammatory bone destruction. However, it also shows that these effects of αGalCer are diminished in RA patients and that this is related to NKT cell dysfunction. These findings provide important information for those searching for novel therapeutic strategies to prevent bone destruction in RA.

Role of Innate T Cells in Anti-Bacterial Immunity

Innate T cells are a heterogeneous group of αβ and γδ T cells that respond rapidly (<2 h) upon activation. These innate T cells also share a non MHC class I or II restriction requirement for antigen recognition. Three major populations within the innate T cell group are recognized, namely, invariant NKT cells, mucosal associated invariant T cells, and gamma delta T cells. These cells recognize foreign/self-lipid presented by non-classical MHC molecules, such as CD1d, MR1, and CD1a. They are activated during the early stages of bacterial infection and act as a bridge between the innate and adaptive immune systems. In this review, we focus on the functional properties of these three innate T cell populations and how they are purposed for antimicrobial defense. Furthermore, we address the mechanisms through which their effector functions are targeted for bacterial control and compare this in human and murine systems. Lastly, we speculate on future roles of these cell types in therapeutic settings such as vaccination.

Exposure of polyethylene particles induces interferon-γ expression in a natural killer T lymphocyte and dendritic cell coculture system in vitro: a preliminary study

Two major issues in total joint arthroplasty are loosening of implants and osteolysis caused by wear particle-induced inflammation. Wear particles stimulate the release of pro-inflammatory cytokines, chemokines, and other inflammatory mediators from macrophages and other cells. Although the biological response of macrophages to wear debris is well established, the role of other cell types such as natural killer T lymphocytes (NKT) and dendritic cells (DCs) is limited. Here we show that ultra-high molecular weight polyethylene (UHMWPE) particles stimulate NKT cells to secrete Interferon-γ (IFN-γ); coculture with DCs further enhanced IFN-γ secretion. Furthermore, UHMWPE particles did not stimulate NKT cells to secrete IL-4, while the NKT cell natural ligand α-galactosylceramide (α-GalCer) treatment in the coculture system significantly enhanced both IFN-γ and IL-4 expression by NKT cells. Comparatively, NKT cells and/or DCs exposed to polymethylmethacrylate particles did not stimulate IFN-γ or IL-4 expression. Mouse bone marrow derived macrophage polarization by lipopolysaccharide and conditioned medium from NKT cells and/or DCs exposed to UHMWPE particles increased tumor necrosis factor-α (TNF-α), but reduced arginase-1 expression in macrophages. The current findings indicate that UHMWPE particles stimulate NKT cells/DCs to produce pro-inflammatory cytokines; this pathway is a novel therapeutic target to mitigate wear particle induced peri-prosthetic osteolysis.

Natural killer cells and natural killer T cells in Lyme arthritis

Introduction

Natural killer (NK) and natural killer T (NKT) cells provide a first line of defense against infection. However, these cells have not yet been examined in patients with Lyme arthritis, a late disease manifestation. Lyme arthritis usually resolves with antibiotic treatment. However, some patients have persistent arthritis after spirochetal killing, which may result from excessive inflammation, immune dysregulation and infection-induced autoimmunity.

Methods

We determined the frequencies and phenotypes of NK cells and invariant NKT (iNKT) cells in paired peripheral blood (PB) and synovial fluid (SF) samples from eight patients with antibiotic-responsive arthritis and fifteen patients with antibiotic-refractory arthritis using flow cytometry and cytokine analyses.

Results

In antibiotic-responsive patients, who were seen during active infection, high frequencies of CD56bright NK cells were found in SF, the inflammatory site, compared with PB (P <0.001); at both sites, a high percentage of cells expressed the activation receptor NKG2D and the chaperone CD94, a low percentage expressed inhibitory killer immunoglobulin-like receptors (KIR), and a high percentage produced IFN-γ. In antibiotic-refractory patients, who were usually evaluated near the conclusion of antibiotics when few if any live spirochetes remained, the phenotype of CD56bright cells in SF was similar to that in patients with antibiotic-responsive arthritis, but the frequency of these cells was significantly less (P = 0.05), and the frequencies of CD56dim NK cells tended to be higher. However, unlike typical NKdim cells, these cells produced large amounts of IFN-γ, suggesting that they were not serving a cytotoxic function. Lastly, iNKT cell frequencies in the SF of antibiotic-responsive patients were significantly greater compared with that of antibiotic-refractory patients where these cells were often absent (P = 0.003).

Conclusions

In patients with antibiotic-responsive arthritis, the high percentage of activated, IFN-γ-producing CD56bright NK cells in SF and the presence of iNKT cells suggest that these cells still have a role in spirochetal killing late in the illness. In patients with antibiotic-refractory arthritis, the frequencies of IFN-γ-producing CD56bright and CD56dim NK cells remained high in SF, even after spirochetal killing, suggesting that these cells contribute to excessive inflammation and immune dysregulation in joints, and iNKT cells, which may have immunomodulatory effects, were often absent.

Proliferatory defect of invariant population and accumulation of non-invariant CD1d-restricted natural killer T cells in the joints of RA patients

OBJECTIVES

While numerical and functional defects of invariant NKT cells have been demonstrated in rheumatoid arthritis (RA), the detailed characterization of proliferative and secretory responses following CD1d-mediated presentation is lacking; the presence of non-invariant populations has never been assessed in human autoimmunity. We have evaluated both invariant and non-invariant populations in the blood and synovial fluid from patients to assess feasibility of NKT cell-directed manipulations in RA.

METHODS

NKT cell populations were quantified by anti-CD4/anti-Vα24 staining and/or CD1d tetramers. Proliferation was measured in cultures of mononuclear cells following stimulations with αGalCer and cytokine secretion determined by multi-bead assay.

RESULTS

We have confirmed a proliferative defect of iNKT cells in both peripheral blood and synovial fluid from RA patients, but no changes in baseline frequencies. Moreover, we have detected an enlargement of non-invariant cell pool in synovial fluid samples. In addition, we noted an evident Th2 shift following exposure to αGalCer and pronounced IL-6 secretion.

CONCLUSIONS

While RA patients suffer from defective proliferative responses of invariant NKT cells, non-invariant cells accumulate at the site of inflammation. While stimulation with αGalCer results in reduced TNF-α and increased suppressive IL-10, abundantly produced IL-6 could potentially contribute to the induction of Th17 cells in the joints.