Cytokines in Rheumatoid Arthritis Margriet J. B. M. Vervoordeldonk, PhD, and Paul P. Tak, MD, PhD

Address Division of Clinical Immunology and Rheumatology, Department of Medicine, Academic Medical Center, University of Amsterdam, PO box 22660, 1100 DD Amsterdam, The Netherlands. E-mail: [email protected] Current Rheumatology Reports 2002, 4:208–217 Current Science Inc. ISSN 1523–3774 Copyright © 2002 by Current Science Inc.

Rheumatoid arthritis (RA) is a chronic disease characterized by synovial inflammation that leads to the destruction of cartilage and bone. In the last decade, there was a lot of successful research in the field of cytokine expression and regulation. It has become clear that pro- and antiinflammatory cytokines, derived predominantely from cells of macrophage lineage, play a major role in the initiation and perpetuation of the chronic inflammatory process in the RA synovial membrane. Monokines are abundant in rheumatoid synovial tissue, whereas low amounts of lymphokines are found. The involvement of pro-inflammatory cytokines, particularly interleukin (IL)-1 and tumor necrosis factor-alpha, in the pathogenesis of RA is well accepted. Recent data provide evidence that the pro-inflammatory cytokine IL-18 plays a crucial role in the development and sustenance of inflammatory joint diseases. There also appears to be a compensatory anti-inflammatory response in RA synovial membrane. It has become clear in the last few years that T cell-derived cytokines expressed preferentially by Th1 cells contribute to joint destruction and inflammation in RA. However, products from Th2 cells may be protective.

Introduction Rheumatoid arthritis (RA) is associated with an increased production of a range of cytokines. The easily accessible rheumatoid synovium has become the most extensively analyzed site to provide insight into the local immune and inflammatory reaction. Analysis of the synovial cell infiltrate in early RA revealed a positive correlation between the scores for local disease activity, the number of macrophages, and interleukin (IL)-6 and tumor necrosis factoralpha (TNFα) expression in the synovium, suggesting that macrophage-derived cytokines play an important role in maintaining clinical signs of inflammation [1,2]. Successful drug treatment of patients with RA is characterized by a decrease in synovial membrane cytokines, including TNFα and IL-1β production. Several cell types produce these

cytokines in rheumatoid synovial tissue. In particular, high levels of IL-1, TNFα, IL-6, IL-15, IL-18, transforming growth factor-beta (TGFβ), and granulocyte-macrophage colonystimulating factor (GM-CSF) are produced in RA synovial tissue. TNFα may be the major cytokine involved in the inflammatory process, whereas IL-1 is a key mediator with regard to cartilage and bone destruction [3,4]. There appears to be a compensatory anti-inflammatory response in the RA synovial membrane, which includes IL-1 receptor antagonist (IL-1RA), p55 and p75 soluble TNF receptors (sTNFR), IL-10, IL-11, and IL-13. The exception is IL-4; this cytokine is rarely present in RA synovium [5]. Furthermore, T cell-derived cytokines, such as IL-17 [6], and counterregulatory cytokines, such as interferon-beta (IFNβ) (van Holten et al., unpublished data) are expressed in the synovium of patients with RA. The complexity of cytokine expression in synovium obscures the role that a single cytokine may play in the pathogenesis of the disease. This review discusses the role of some recently discovered cytokines in RA synovium and briefly mentions the role of other cytokines. Table 1 provides an overview of these cytokines. Although chemokines and chemoattractants, such as IL-8, macrophage inflammatory protein (MIP-1), and monocyte chemoattractant protein (MCP-1), are expressed in the synovium and play an important role in the pathogenesis, they are not the subject of this review. Their role has been reviewed extensively in other publications [7].

Pro-inflammatory Cytokines Tumor necrosis factor-alpha and interleukin-1 Tumor necrosis factor-alpha and IL-1 are thought to play a key role in inflammation and joint damage that occur in RA. The pathologic effects caused by these cytokines include leukocytic infiltration leading to synovial hyperplasia, cell activation, cartilage breakdown, and inhibition of cartilage matrix synthesis. Despite the similarities of their effects, in vitro studies suggest that TNFα seems to be important because of its place in the hierarchy of the cascade that regulates the production of pro-inflammatory cytokines in the rheumatoid synovial tissue [8]. For example, TNFα controls the production of IL-1 and other pro-inflammatory cytokines, including IL-6 and IL-8. Furthermore, it increases the expression of adhesion molecul es, pr os t agl andi n E 2 (PGE 2 ), and matri x metalloproteinases (MMPs). IL-1 shares many biologic functions with TNFα and is potent in inducing damage to cartilage and bone [3], because it induces proteoglycan

FLS, macrophages Macrophages, dendritic cells FLS, macrophages Activated memory CD4+ T cells Macrophages

IL-6

IL-12

IL-15

IL-17

IL-18

No expression in RA synovium Th2 cells, macrophages, B cells FLS Th2 cells

IL-4

IL-10 IL-11

IL-13

Inhibits proliferation of lymphocytes; inhibits cartilage and bone destruction; high concentrations of TGF␤ can be pro-inflammatory Down-regulates pro-inflammatory cytokines, expression of adhesion molecules, and activation markers; enhances production of IL-10 and IL-1RA; inhibits T-cell proliferation and migration; inhibits MMP activity Antagonizes Th1 responses by direct inhibition of IFN␥ production, thereby shifting the Th1/Th2 balance; inhibits production of pro-inflammatory cytokines by macrophages and induces expression of IL-1RA; inhibits bone resorption and suppresses MMP production Shares many properties with IL-4; at high concentrations can induce IL-1␤ and IL-6 synthesis Decreases the production of TNF and IL from activated macrophages; inhibits NF␬B binding activity; prevents joint damage Shares many properties with IL-4, but cannot act directly on T cells

Induces synthesis of pro-inflammatory cytokines, chemokines, and adhesion molecules; stimulates production and release of MMPs, PGE2, and NO; promotes bone resorption; inhibits production of matrix components Shares many actions with TNF␣. Induces synthesis of pro-inflammatory cytokines, but not TNF␣; is more potent than TNF␣ in inducing cartilage destruction Exerts pro- and anti-inflammatory effects, including activation of T and B cells, induction of chemokines on endothelial cells, activation of osteoclasts to absorb bone, suppression of proinflammatory cytokine production, and induction of IL-1RA production Promotes development of Th1 responses; induces production of IFN␥; activates NK cells and T cells; acts in synergy with IL-18 T-cell chemoattractant and activator; an indirect enhancer of cytokine and chemokine production by macrophages; induces B-cell maturation and isotype switching; enhances NK cell cytotoxicity Induces secretion of cytokines and growth factors by endothelial, epithelial, and fibroblastic stromal cells and macrophages; suppresses matrix synthesis in vitro; induces expression of RANKL Synergistic effect with IL-12 to increase IFN␥ production, NK cell cytotoxicity, and Th1 responses; can induce Th2 responses depending on its cytokine milieu; induces production of chemokines and pro-inflammatory cytokines; acts as angiogenic factor

Major actions

CRP—C-reactive protein; FLS—fibroblast-like synoviocytes; IFN—interferon; IL—interleukin; IL-1RA—interleukin-1 receptor antagonist; MMP—matrix metalloproteinase; NF␬B—nuclear factor kappaB; NK—natural killer; NO—nitric oxide; PGE2—prostaglandin E2; RANKL—receptor activator of NF␬B ligand; RA—rheumatoid arthritis; Th—T helper; TGF␤—transforming growth factor-beta; TNF␣—tumor necrosis factor-alpha.

FLS

IFN␤

Anti-inflammatory and immunoregulatory TGF␤ Macrophages

Macrophages

Macrophages

Pro-inflammatory TNF␣

IL-1

Main producing cells in RA synovial tissue

Cytokine

Table 1. Cytokine expression and function in rheumatoid synovium

Cytokines in Rheumatoid Arthritis • Vervoordeldonk and Tak 209

210

Rheumatoid Arthritis

degradation and inhibits proteoglycan synthesis. In addition, IL-1 induces the production of the MMPs stromelysin and collagenase and enhances bone resorption. Both cytokines are found at high levels in the synovial fluid of patients with RA. In RA, TNFα is mostly produced by macrophages in the synovial membrane and at the cartilage-pannus junction. Two distinct TNF receptors, p55 and p75, are expressed on the surface of a variety of cells, including fibroblast-like synoviocytes [9]. sTNFRs have been detected at high levels in the synovial fluid of patients with RA. sTNFR may play a regulatory role in normal physiologic responses by binding excess extracellular TNFα. Interleukin-1 is expressed within the synovial membrane and in blood mononuclear cells [10]. Two IL-1 receptors have been detected on the cell surface. Soluble forms have been identified in plasma [9]. Only the type I receptor appears to mediate signal transduction, whereas the type II receptor may act as a decoy. There is a natural inhibitor of IL-1, referred to as IL-1 receptor antagonist (IL1RA) [11]. Endogenous production of IL-1RA is an important anti-inflammatory mechanism in animal models and in human disease. In the RA synovium, an imbalance exists in this system because the IL-1RA levels are insufficient to effectively block the pro-inflammatory effects of IL-1 [12]. In vitro data suggest that a biologic response can occur when only 2% to 3% of the IL-1 receptors (IL-1Rs) are occupied by IL-1. Therefore, up to 98% of all IL-1Rs may need to be occupied by IL-1RA before an antagonistic effect is observed. The importance of TNFα in RA is evidenced by several experimental and clinical observations. In vitro, neutralization of TNFα resulted in decreased production of IL-1, IL-6, IL-8, and GM-CSF in synovial cell cultures [8]. Several independent in vivo studies demonstrated that neutralization of TNFα before the onset of the disease suppressed collageninduced arthritis (CIA) in mice. TNFα blockade after the onset of disease resulted in amelioration of clinical symptoms and prevention of joint destruction [13,14]. In a murine model, overexpression of the human TNFα transgene caused the development of a destructive form of polyarthritis 4 to 6 weeks after birth [15]. This could be prevented by administration of a human TNFα-specific monoclonal antibody. Evidence that TNFα exerted its pathogenic effect in part through IL-1 was provided by the therapeutic benefit observed with anti–IL-1R antibody [16], reflecting the cytokine hierarchy observed in RA cultures. Studies in animal models of arthritis have demonstrated an important role for IL-1 in RA. In mice, intraarticular injections of IL-1 caused active synovitis and marked depletion of cartilage matrix [17]. Human IL-1α overproduction in mice induced chronic inflammatory polyarthritis with remarkable synovial proliferation and severe bone and cartilage destruction [18]. The use of genetically modified mice demonstrated the physiologic significance of IL-1RA because deletion of this gene in mice resulted in the spontaneous development of arthritis [19].

In vivo studies have demonstrated the therapeutic potential of IL-1 blockade [3]. Human IL-1RA gene transfer into fibroblast-like synoviocytes prevented cartilage destruction in human cartilage that was co-implanted with the transduced cells in SCID mice [20]. Studies of CIA in mice revealed that blocking IL-1 activity can reduce the severity of synovitis and prevent cartilage and bone destruction [3]. Therapeutic approaches in RA have focused mainly on TNFα; anti-TNF therapy shows efficacy in most patients with RA [21,22,23•]. The investigated approaches include sTNFR (ie, etanercept) and monoclonal antibodies against TNFα (ie, infliximab). Clinical investigations in which the activity of TNFα in patients with RA was blocked by intravenously administered infliximab provided evidence that TNF regulates IL-1, IL-6, IL-8, MCP-1, vascular endothelial growth factor production, recruitment of immune and inflammatory cells into the joints, angiogenesis, and reduction of serum levels of MMP-1 and -3. Randomized placebo-controlled, multicenter clinical trials of human TNF inhibitors have demonstrated their consistent and remarkable efficacy in controlling signs and symptoms, with a favorable safety profile, in approximately 70% of the patients and their ability to retard joint damage [23•]. Soluble IL-1R (sIL-1R) and IL-1RA have been tested in clinical trials [9]. In studies in which recombinant human soluble type I IL-1R was administered to patients with active RA, no clinical improvement was observed. This may be explained by the high affinity of sIL-1R for IL-1RA, thus scavenging the endogenous IL-1 inhibitor. Targeted therapy with IL-1RA significantly reduced joint erosions, but the effect on joint inflammation was limited [24]. Two large well-controlled studies in patients with RA led to the conclusion that IL-1RA is clinically effective, safe, and welltolerated [25]. The observation that anti-TNF therapy combined with methotrexate shows an unexpected degree of protective effect on the joints could suggest that that the additional benefit from targeting other anticytokines may be small. However, at least 30% of the RA does not respond satisfactorily to TNFα blockade with regard to inhibition of arthritis activity. Anti–IL-1 therapy may prove beneficial in patients unresponsive to anti-TNF therapy or in combination with TNFα blockade. Interleukin-6 Interleukin-6 is one member of a family of related cytokines (IL-6, IL-11, oncostatin M, and leukocyte inhibitory factor) that share the gp130 signaling receptor unit. IL-6 appears to have different actions on different cell types and can promote or suppress arthritis. IL-6 activates T and B cells, induces chemokine expression on endothelial cells, and activates osteoclasts to absorb bone. The reported antiinflammatory effects of IL-6 include induction of antiinflammatory cytokines (such as IL-1RA) and acute phase reactants that subserve anti-inflammatory functions, suppression of cytokine production (IL-1, TNF, and IL-12) and adhesion molecule expression, inhibition of protease

Cytokines in Rheumatoid Arthritis • Vervoordeldonk and Tak

expression, and induction of protease inhibitors in RA fibroblast-like synoviocytes. Interleukin-6 levels are highly elevated in RA, especially in the synovial fluid and tissue during active disease. In RA, IL-6 is mostly produced by fibroblast-like synoviocytes and partly by other cells present in the RA synovium, such as macrophages. IL-6 levels in the synovial fluid correlate with the degree of radiologic joint damage. Synovial tissue levels are associated with arthritis activity [1]. However, direct involvement of IL-6 in joint destruction is controversial. Interleukin-6 appears to be critical in the initiation phase of CIA, which is mediated by lymphocyte responses against type II collagen [26]. However, consistent with the anti-inflammatory effects of IL-6, reduced cartilage destruction was found during experimental arthritis in IL-6 gene knockout mice [27]. Mice containing a mutation that partially abrogates IL-6 signal transduction spontaneously developed arthritis [28]. Despite the anti-inflammatory properties of IL-6, clinical improvement has been reported in a small, uncontrolled group of patients with active RA after 10 consecutive days of once-daily intravenous injection of murine anti–IL6 monoclonal antibody (mAB) [29]. In a Japanese openlabel study using humanized anti–IL-6R mAb to treat patients with severe RA, clinical symptoms improved within 1 week of treatment. Therapeutic efficacy was maintained over 6 months of continuous treatment without major adverse events [30]. Thus IL-6 blockade could provide a promising novel anti-rheumatic treatment. Interleukin-12 Interleukin-12 is a potent inducer of cell-mediated immunity by promoting differentiation of Th0 cells into Th1type cells, and activating natural killer (NK) cells and CD8+ cells. In RA, IL-12 acts synergistically with IL-18 in the induction of Th1 responses. IL-12 is produced by activated macrophages, dendritic cells, and to a lesser extent by granulocytes. The active IL-12 is a heterodimer (p70) composed of a p35 and a p40 subunit. The p40 subunit is important for receptor binding. It has been demonstrated that the expression of p35 and p40 is differentially regulated. Homodimers of p40 are produced in excess over p70 heterodimers, and may antagonize bioactive IL-12p70 by competitive binding to the IL-12 receptor. Expression of IL12 has been shown in the synovial tissue of patients with RA [31]. Through immunohistochemical analysis, IL-12– producing cells were localized mainly in the sublining layer of RA synovium, mostly in CD68+ macrophages. Levels of IFNγ production by RA synovial tissue cells were potently and selectively enhanced by IL-12. An important role for IL-12 in the development of arthritis has been shown in the murine CIA model. Blockade of IL-12 during the induction of CIA, using neutralizing antibodies, markedly attenuated the severity of arthritis clinically and histopathologically [32]. The incidence and overall severity of CIA were significantly reduced in IL-12–deficient mice

211

[33]. Furthermore, a recent study revealed that local delivery of IL-12p40 by retroviral-transduced type II collagenspecific T cells ameliorated CIA [34]. However, IL-12 had a suppressive role in the established phase of CIA [35]. These studies suggest that inhibition of IL-12 activity could have a beneficial effect in RA. Interleukin-15 Interleukin-15 is a cytokine that shares biologic activities with IL-2. IL-15 uses the IL-2Rβ and common γ-chain subunits in combination with a unique α-chain, IL-15Rα, for signaling. IL-15 can exert a variety of immunologic effects. IL-15 serves as a powerful T-cell chemoattractant and activator and induces B-cell maturation and isotype switching. It activates neutrophils and NK cell proliferation, cytotoxicity and cytokine production, and regulates NK cell/macrophage interaction [36]. Activation of T cells by IL-15 increases their ability to stimulate TNFα, IL-1, IL-8, and MCP-1, but does not increase IL-10 production by macrophages. Because IL15 is produced by macrophages, this cytokine may contribute to a self-perpetuating pro-inflammatory loop through restimulation of T cells. IL-15 may be generated by cells within the immune system and by cells belonging to other tissues, including keratinocytes and synoviocytes [37]. Immunohistochemically, IL-15 can be detected in the RA synovial membrane, where it is localized to macrophages and fibroblast-like synoviocytes in the synovial lining layer and within lymphocytic aggregates [38]. IL-15 expression is significantly increased in RA synovium compared with reactive arthritis and osteoarthritis [37]. Furthermore, the concentration of this cytokine is elevated in the synovial fluid of patients with RA compared with patients with osteoarthritis (OA) [39,40]. Elevated levels of IL-15 were present in the serum of patients with RA, but not in that of patients with OA [39]. Fibroblast-like synoviocytes isolated from joints of patients with RA spontaneously secrete large amounts of IL-15 that may be increased after stimulation with TNFα and IL-1β [41]. The induction of macrophage-derived TNFα production in response to IL-15–activated T cells from patients with RA depends on cell contact [40]. Therefore, IL-15 can act upstream of TNFα, orchestrating the production of inflammatory cytokines in the inflamed RA synovium. In vivo studies revealed direct evidence that IL-15 can play an important role in arthritis. Using the soluble IL-15Rα chain, the development of murine CIA was prevented with marked inhibition of the onset of the Th1 cell-mediated anticollagen response [42•]. Because of the potential role in the perpetuation of synovial inflammation in RA, apparently operating upstream of TNFα, IL-15 is another cytokine that may be blocked in future studies in patients with RA. Interleukin-17 Interleukin-17 is a recently discovered cytokine that is secreted by a restricted set of cells, whereas its receptor is

212

Rheumatoid Arthritis

ubiquitously expressed on many cell types. T lymphocytes, particularly the activated memory CD4+ T-cell subset, are the major source of IL-17 [6]. IL-17 may play an upstream role in T cell-triggered inflammation by stimulating stromal cells to secrete other cytokines and growth factors. IL17 can induce IL-6, IL-8, granulocyte colony-stimulating factor (G-CSF), and PGE2 secretion from epithelial, endothelial, and fibroblastic stromal cells, and TNFα and IL-1 production by macrophages. A pro-inflammatory role of IL-17 is suggested by its capacity to induce neutrophil recruitment through chemokine release [43] and stimulation of granulopoiesis [44]. Interleukin-17 has been demonstrated in the synovium of patients with RA [45]. Synovial fluid levels of IL-17 are much higher in RA than in OA. The presence of the IL-17 receptor (IL-17R) has been demonstrated in vitro on the surface of various cells of human origin such as NK cells, fibroblasts and fibroblast-like synoviocytes, macrophages, osteoclasts, and stromal cells [46]. However, in the synovium, IL-17R was expressed almost exclusively by endothelial cells and had low expression on chondrocytes. IL-17R expression was observed in most patients with various arthritides. Interleukin-17 shares many properties with IL-1, suggesting that infiltrated IL-17–producing Th1 cells may contribute to cartilage damage. In vitro, it has been shown that IL-17 suppresses matrix synthesis by articular chondrocytes through induction of nitric oxide (NO) production [47•]. Furthermore, IL-17 induced the expression of receptor activator of nuclear factor kappaB (NFκB) ligand (RANKL; also known as OPGL, TRANCE, or ODF) [48]. This TNF-related cytokine plays an important role in bone resorption. In addition, IL-17 dose-dependently induces expression of RANKL mRNA in osteoblasts. These observations indicate that IL-17 may promote joint inflammation and tissue destruction, a notion supported by recent in vivo studies. Local overexpression of IL-17 was shown to promote destructive arthritis in mice with CIA [49]. Conversely, blocking IL-17 significantly reduced CIA, including protection against joint damage. IL-17 blockade reduced inflammation and joint damage in adjuvant arthritis in rats [50]. Because IL-17 shows synergy with IL-1 in cartilage destruction, low levels of IL17 and IL-1 may have additive or synergistic effects [51]. Blocking IL-1 had no effect on IL-17–induced inflammation and joint damage, suggesting a partially IL-1– independent role for IL-17 [49]. The synergistic or additive effects of IL-17, IL-1, and TNFα suggest that strategies targeting multiple pro-inflammatory pathways may be more effective than those targeting a single effector mechanism. In vitro data suggest that the combination of sTNFR, sIL-17R, and sIL-RII may be synergistic in controlling synovial inflammation and bone resorption [52•]. Taken together, these studies suggest the potential role of IL-17 blockade as a novel strategy for the treatment of T cell-mediated conditions.

Interleukin-18 Interleukin-18 is a cytokine of the IL-1 protein family that may be involved in several immune-mediated diseases, including RA [53]. Similar to the IL-1β precursor, the IL-18 precursor (pro–IL-18) lacks a signal peptide and requires caspase-1 (also known as IL-1β–converting enzyme [ICE]) for cleavage and release of the mature molecule from the intracellular compartment. IL-18 expression has been identified in various cells, including macrophages, dendritic cells, Kupffer cells, keratinocytes, chondrocytes, fibroblast-like synoviocytes, and osteoblasts. The IL-18 receptor (IL-18R) consists of two amino acid chains, IL18Rα and IL-18Rβ, which are members of the IL-1 receptor family. The IL-18R is present on T and B cells, NK cells, macrophages, fibroblast-like synoviocytes, neutrophils, and chondrocytes. IL-18R signals through the IL-1 pathway to activate NFκB. Interleukin-18 is overexpressed in RA synovium, but not in OA synovium [53]. In the RA synovial membrane, IL-18 is localized in the CD68+ cells of dendritic morphology in aggregates, in intimal macrophages, and in fibroblast-like synoviocytes. Pro–IL-18 and mature IL-18 can be detected in synovial biopsy specimens by Western blot analysis. In addition, increased serum levels of IL-18 are present in patients with RA. IL-18Rα is expressed by synovial lymphocytes and macrophages. Interleukin-18 is a strong inducer of IFNγ production by T cells and NK cells and enhances the cytotoxicity in acquired and innate immunity. IL-18 acts directly as a proinflammatory cytokine by inducing CC and CXC chemokines and IL-18 production [54]. IL-18 also induces the production of TNFα , IL-1β , GM-CSF, IL-2, PGE2, and inducible NO. A counterregulatory loop may exist through NO production because NO inhibits ICE, which is necessary to process pro–IL-18. There is remarkable synergy between IL-12 and IL-18 in the induction of Th1 cells because of a reciprocal regulation of the receptors. Although most published reports link IL-18 with Th1associated functions, IL-18 has recently been shown also to augment Th2 responses, suggesting a broader role in T-cell maturation [54]. IL-18 promotes other activities relevant to disease pathogenesis. Recently, a novel role for IL-18 has been reported as an angiogenic factor [55•] and activator of neutrophils [56]. In addition, IL-18 was shown to reduce chondrocyte proliferation, up-regulate stromelysin expression, and enhance glucosaminoglycan release [57]. Not all activities are pro-inflammatory. IL-18 may inhibit osteoclast maturation through GM-CSF and suppress cyclooxygenase-2 (COX-2) expression through IFNγ synthesis [58]. However, in vivo data indicate that the net effect of IL-18 in the development of arthritis is proinflammatory. IL-18 plays an important role in the development of CIA and streptococcal cell wall (SCW) arthritis in mice [59,60]. IL-18 administration promoted the development of collagen-induced erosive arthritis [59], predominantly by driving TNFα production. The role of IL-18 in

Cytokines in Rheumatoid Arthritis • Vervoordeldonk and Tak

articular inflammation was confirmed in mice lacking the IL-18 gene that had a reduced incidence and severity of CIA, which was reversed by treatment with recombinant IL-18 [61•]. The absence of IL-18 was associated with reduced TNFα expression and decreased collagen-specific Th1 responses in vitro. In the SCW model, the role of endogenous IL-18 was investigated by neutralization of IL18 before induction of arthritis. IL-18 blockade ameliorated joint pathology by reducing TNFα and IL-1 levels. This role for IL-18 was shown to be IFNγ independent [60]. Recently, IL-18 binding protein (IL-18BP) was described as a novel modulator of the Th1 cytokine response. IL-18BP is not a variant of a cell surface receptor, but a part of a novel family of secreted proteins. In animal models, IL-18BP blocks 90% of IFNγ production after lipopolysaccharide (LPS) injection [54]. In preliminary studies in established murine CIA, IL-18 blockade through polyclonal antibody or recombinant human IL-18BP significantly reduced clinical scores and protected against joint damage [62]. It remains to be shown if IL-18BP will be useful for the treatment of patients with RA or other Th1-related diseases.

Anti-inflammatory and Immunoregulatory Cytokines Transforming growth factor-beta Transforming growth factor-beta is a potent immunomodulator with pro- and anti-inflammatory activities. In vitro, TGFβ isoforms exert effects that can be grouped into three broad areas: modulation of inflammatory cell function, growth inhibition and differentiation, and control of extracellular matrix production. Studies in animals and humans strongly suggest that TGFβ is important in the pathogenesis of several disorders, including RA. In RA, different forms of TGFβ and its receptors are expressed by macrophages in the intimal lining layer, synovial sublining, and the cartilagepannus junction. In the synovial fluid, there are elevated levels of TGFβ. In animal models, TGFβ is able to induce synovial inflammation but may suppress acute and chronic arthritis. Systemic administration of TGFβ has been shown to reverse inflammation and immune-mediated pathology in vivo. In addition, systemic delivery of DNA-encoding TGFβ was shown to suppress chronic disease in rats with SCWinduced arthritis [63]. The route of administration appears to be critical because, in contrast to systemic delivery, direct local injection of TGFβ into the joint could elicit an arthritic response [64]. Furthermore, it was reported that local injection of TGFβ enhanced fibrosis [65] and that overexpression of TGFβ in the murine knee joint may induce chondro-osteophyte formation [66]. These studies indicate a dual role for TGFβ in arthritis. TGFβ has other pro-inflammatory effects, such as chemotactic effects on monocytes. Recently, it was shown that TGFβ also contributes to the inappropriate retention of T cells within the

213

synovial microenvironment [67]. Consistent with its dual role are the effects of TGFβ on MMPs. While inhibition of gelatinase B and collagenase suggests a protective role in tissue destruction, the increase in collagenase-3 in chondrocytes may exacerbate cartilage damage. Although experimental data show a dual activity for TGFβ in arthritis, the repeated demonstration that systemically delivered TGFβ can effectively control autoimmune pathology, including arthritic lesions, suggests that TGFβ may be a potential candidate to develop for therapeutic purposes. Interferon-beta Interferons are a family of naturally secreted proteins with immunomodulatory functions. IFNβ appears to downregulate the pro-inflammatory cytokines IL-1β and TNFα, and enhances IL-10 and IL-1RA production. In addition, IFNβ may down-regulate activation antigens and expression of several adhesion molecules, resulting in inhibition of Tcell proliferation and migration. However, IFNβ may also contribute to the persistence of memory T cells by its ability to prevent apoptosis in these cells [68]. IFNβ has other activities that may be involved in the pathogenesis of RA. IFNβ could down-regulate basic fibroblast growth factor (bFGF), which is important in angiogenesis. Furthermore, IFNβ therapy may protect against cartilage destruction by inhibition of MMP activity in patients with RA. A recent study examined the effect of IFNβ gene therapy in CIA in DBA/1 mice [69]. IFNβ-expressing fibroblasts were injected intraperitoneally into mice with CIA before or after the onset of arthritis. The transfected cells produced constant levels of IFNβ, which may be an advantage considering the short half-life of the compound. One injection of IFNβ-secreting fibroblasts was sufficient to prevent arthritis or ameliorate existing disease. Little is known about the effects of systemic administration of exogenous IFNβ on arthritis activity. One study recently revealed that daily injections with IFNβ led to a significant decrease in synovial inflammation and joint destruction in murine [70]. A similar beneficial effect was shown in CIA in rhesus monkeys [71]. Pilot studies in RA [71] and juvenile rheumatoid arthritis [72] confirmed the potential of IFNβ therapy for the treatment of chronic arthritis. A placebocontrolled study on the effects of IFNβ in patients with RA is in progress. Interleukin-4, -10, and -13 Interleukin-4 and IL-10 may have major roles as antiinflammatory cytokines [73]. IL-4 is a potent mediator able to shift the balance of Th1/Th2 cells, and is produced specifically by Th2 cells. IL-4 antagonizes Th1 responses by direct inhibition of IFNγ production by activated T cells. IL4 down-regulates monocyte/macrophage cytotoxicity, cytokine production (including TNFα and IL-1), and IL15–induced cytokine production. In addition, IL-4 induces expression of IL-1RA by activated macrophages. IL-4 also has effects on the integrity of cartilage and bone. This may

214

Rheumatoid Arthritis

be explained in part by the suppression of MMP production by monocytes and inhibition of osteoclast activity and survival, thereby blocking bone resorption. There is little IL-4 in the RA synovium, which is in agreement with the predominant Th1 response [5]. In contrast to IL-4, IL-13 (another Th2-like cytokine) has been detected at low concentrations in rheumatoid synovium and synovial fluid of patients with RA. IL-13 is strongly homologous with IL-4. Both cytokines share many functions as a result of shared receptors. IL-13 has profound effects on monocytes in vitro, deactivating them and acting in a complex manner to change monocytic morphology, phenotype, function, and cytokine production. IL-13 profoundly inhibited the production of proinflammatory cytokines by LPS-stimulated monocytes. IL13 can maintain this anti-inflammatory property in vivo, as demonstrated by suppression of experimental autoimmune encephalomyelitis in rats. IL-13 can significantly decrease quantities of IL-1β, TNFα, and several chemokines by RA synovial tissue explants when administered through ex vivo gene therapy [74]. In combination with its ability to reduce CIA in vivo [75], IL-13 appears worthy of future considerations as a therapeutic agent for RA. Interleukin-10 cannot be considered a specific Th2 cytokine because it can also be produced by B cells, monocyte/ macrophages, and Th1-like cells. Although IL-10 is produced in substantial amounts in RA synovium and synovial fluid, the levels are insufficient to control inflammation. IL-10 shares many properties with IL-4, such as suppression of IL-1 and TNFα production. In addition, IL-10 has an inhibitory effect on the production of destructive enzymes, by direct inhibition of monocyte/macrophages and suppression of pro-inflammatory cytokines. Furthermore, IL-10 induces the expression of tissue inhibitor of metalloproteinase 1 (TIMP1) by monocytes. Interleukin-4 and IL-10 may be capable of preventing joint destruction, a view supported by studies in animal models. Transferring anti-inflammatory cytokine genes, such as IL-4 and IL-10, resulted in anti-arthritic effects in experimental models of RA [73]. Cartilage destruction and subchondral bone erosion as a result of CIA were significantly reduced by administration of IL-4 and IL-10 gene therapy. The anti-arthritic effect was more pronounced after systemic administration of dendritic cells genetically engineered to express IL-4 [76]. Similarly, adenoviral IL-4 gene therapy had a beneficial effect on rat adjuvant arthritis [77]. Joint abnormalities of CIA were prevented by the combined administration of IL-4 and IL-10 [73]. Although IL-4 and IL-10 inhibit inflammatory responses in vitro and in vivo in experimental animal models, the clinical benefit of systemic treatment with either cytokine is limited in the treatment of RA. Clinical trials with human IL-4 [78] or IL-10 [79] in patients with RA have shown diverse responses and limited disease suppression because these cytokines have some potentially proinflammatory properties. IL-4/IL-10 combination therapy

may be beneficial because the partial pro-inflammatory effects of the one could be inhibited by the other [73]. This approach has not been tested in patients with RA. Interleukin-11 Interleukin-11 is a pleiotropic cytokine that regulates the growth and development of hematopoietic stem cells and decreases the pro-inflammatory mediators of cytokine and NO production. IL-11 has anti-inflammatory effects, especially on macrophages and fibroblasts, and suppresses the expression of IL-12, IFNγ, TNFα, adhesion molecules, and proteases. Interleukin-11 is present in the serum, synovial fluid, and synovial membrane of patients with RA [80]. Treatment with recombinant human IL-11 (rH-IL-11) decreased the production of TNFα, IL-1β, and NFκB-binding activity in RA synovium in vitro [80]. rH-IL-11 therapy inhibited clinical severity and prevented joint damage in murine CIA and adjuvant-induced arthritis [81]. However, no therapeutic benefit of rH-IL-11 therapy has been detected in a phase I/II trial in patients with RA [82]. Larger clinical trials with rH-IL-11 using different dosing regimens may provide more definitive data on the efficacy of rH-IL-11 in the treatment of patients with RA.

Conclusions Cytokines play a crucial role in the pathogenesis of RA. The recent advent of TNFα and IL-1 blockade to the clinic has shown the therapeutic potential of targeting specific cytokines. Newly discovered cytokines such as IL-15, IL-17, and IL-18 may be valuable targets for the treatment of chronic destructive arthritis. The function of these cytokines has been evaluated in vitro. Some preclinical studies demonstrated amelioration of arthritis in experimental models after interfering with these cytokines. An alternative approach could be to apply immunomodulatory cytokines such as IL-4, IL-10, IL-11, and IFNβ. Combination therapy using biologics targeting various cytokines may emerge, although its use may be limited by cost and potential side effects. The development of targeted small molecules interfering with signal transduction pathways involved in cytokine production or inhibiting migration of cytokineproducing effector cells may provide another approach to regulate cytokine balance at the site of inflammation. Some of these therapies will likely improve our ability to reduce synovial inflammation and to protect the joints.

References and Recommended Reading Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance 1.

Tak PP, Smeets TJ, Daha MR, et al.: Analysis of the synovial cellular infiltrate in early rheumatoid synovial tissue in relation to disease activity. Arthritis Rheum 1997, 40:217–225.

Cytokines in Rheumatoid Arthritis • Vervoordeldonk and Tak

2.

3. 4.

5.

6.

7.

8.

9. 10.

11.

12.

13.

14.

15.

16.

17.

18.

19. 20.

21.

22.

Kraan MC, Patel DD, Haringman JJ, et al.: The development of clinical signs of rheumatoid synovial inflammation is associated with increased synthesis of the chemokine CXCL8 (interleukin-8). Arthritis Res 2001, 3:65–71. van den Berg WB: Anti-cytokine therapy in chronic destructive arthritis. Arthritis Res 2001, 3:18–26. Tak PP, Bresnihan B: The pathogenesis and prevention of joint damage in rheumatoid arthritis: advances from synovial biopsy and tissue analysis. Arthritis Rheum 2000, 43:2619–2633. Smeets TJ, Dolhain RJ, Breedveld FC, Tak PP: Analysis of the cellular infiltrates and expression of cytokines in synovial tissue from patients with rheumatoid arthritis and reactive arthritis. J Pathol 1998, 186:75–81. Aarvak T, Chabaud M, Miossec P, Natvig JB: IL-17 is produced by some proinflammatory Th1/Th0 cells but not by Th2 cells. J Immunol 1999, 162:1246–1251. Szekanecz Z, Strieter RM, Kunkel SL, Koch AE: Chemokines in rheumatoid arthritis. Springer Semin Immunopathol 1998, 20:115–132. Maini RN, Elliott M, Brennan FM, Williams RO, Feldmann M: TNF blockade in rheumatoid arthritis: implications for therapy and pathogenesis. APMIS 1997, 105:257–263. Carteron NL: Cytokines in rheumatoid arthritis: trials and tribulations. Mol Med Today 2000, 6:315–323. Ulfgren AK, Grondal L, Lindblad S, et al.: Interindividual and intra-articular variation of proinflammatory cytokines in patients with rheumatoid arthritis: potential implications for treatment. Ann Rheum Dis 2000, 59:439–447. Arend WP: Cytokine imbalance in the pathogenesis of rheumatoid arthritis: the role of interleukin-1 receptor antagonist. Semin Arthritis Rheum 2001, 30:1–6. Firestein GS, Boyle DL, Yu C, et al.: Synovial interleukin-1 receptor antagonist and interleukin-1 balance in rheumatoid arthritis. Arthritis Rheum 1994, 37:644–652. Williams RO, Feldmann M, Maini RN: Anti-tumor necrosis factor ameliorates joint disease in murine collagen-induced arthritis. Proc Natl Acad Sci U S A 1992, 89:9784–9788. Thorbecke GJ, Shah R, Leu CH, et al.: Involvement of endogenous tumor necrosis factor alpha and transforming growth factor beta during induction of collagen type II arthritis in mice. Proc Natl Acad Sci U S A 1992, 89:7375–7379. Keffer J, Probert L, Cazlaris H, et al.: Transgenic mice expressing human tumour necrosis factor: a predictive genetic model of arthritis. EMBO J 1991, 10:4025–4031. Probert L, Plows D, Kontogeorgos G, Kollias G: The type I interleukin-1 receptor acts in series with tumor necrosis factor (TNF) to induce arthritis in TNF-transgenic mice. Eur J Immunol 1995, 25:1794–1797. van de Loo AA, van den Berg WB: Effects of murine recombinant interleukin 1 on synovial joints in mice: measurement of patellar cartilage metabolism and joint inflammation. Ann Rheum Dis 1990, 49:238–245. Niki Y, Yamada H, Seki S, et al.: Macrophage- and neutrophildominant arthritis in human IL-1 alpha transgenic mice. J Clin Invest 2001, 107:1127–1135. Luster AD: Chemokines—chemotactic cytokines that mediate inflammation. N Engl J Med 1998, 338:436–445. Muller-Ladner U, Roberts CR, Franklin BN, et al.: Human IL1Ra gene transfer into human synovial fibroblasts is chondroprotective. J Immunol 1997, 158:3492–3498. Maini R, St Clair EW, Breedveld F, et al.: Infliximab (chimeric anti-tumour necrosis factor alpha monoclonal antibody) versus placebo in rheumatoid arthritis patients receiving concomitant methotrexate: a randomised phase III trial. ATTRACT Study Group. Lancet 1999, 354:1932–1939. Bathon JM, Martin RW, Fleischmann RM, et al.: A comparison of etanercept and methotrexate in patients with early rheumatoid arthritis. N Engl J Med 2000, 343:1586–1593.

215

23.• Feldmann M, Maini RN: Anti-TNF alpha therapy of rheumatoid arthritis: what have we learned? Annu Rev Immunol 2001, 19:163–196. This review provides a nice overview of inhibitors of tumor necrosis factor-alpha in clinical use and their mechanism of action. 24. Bresnihan B: The safety and efficacy of interleukin-1 receptor antagonist in the treatment of rheumatoid arthritis. Semin Arthritis Rheum 2001, 30:17–20. 25. Dayer JM, Feige U, Edwards CK 3rd, Burger D: Anti-interleukin1 therapy in rheumatic diseases. Curr Opin Rheumatol 2001, 13:170–176. 26. Alonzi T, Fattori E, Lazzaro D, et al.: Interleukin 6 is required for the development of collagen-induced arthritis. J Exp Med 1998, 187:461–468. 27. van de Loo FA, Kuiper S, van Enckevort FH, Arntz OJ, van den Berg WB: Interleukin-6 reduces cartilage destruction during experimental arthritis: a study in interleukin-6-deficient mice. Am J Pathol 1997, 151:177–191. 28. Ernst M, Inglese M, Waring P, et al.: Defective gp130-mediated signal transducer and activator of transcription (STAT) signaling results in degenerative joint disease, gastrointestinal ulceration, and failure of uterine implantation. J Exp Med 2001, 194:189–203. 29. Taylor PC, Williams RO, Maini RN: Immunotherapy for rheumatoid arthritis. Curr Opin Immunol 2001, 13:611–616. 30. Nishimoto N, Maede K, Kuritani T, et al.: Safety and efficacy of repetitive treatment with humanized anti-interleukin-6 receptor antibody (MRA) in rheumatoid arthritis [abstract]. Arthritis Rheum 2001, 44:S84. 31. Morita Y, Yamamura M, Nishida K, et al.: Expression of interleukin-12 in synovial tissue from patients with rheumatoid arthritis. Arthritis Rheum 1998, 41:306–314. 32. Malfait AM, Butler DM, Presky DH, et al.: Blockade of IL-12 during the induction of collagen-induced arthritis (CIA) markedly attenuates the severity of the arthritis. Clin Exp Immunol 1998, 111:377–383. 33. McIntyre KW, Shuster DJ, Gillooly KM, et al.: Reduced incidence and severity of collagen-induced arthritis in interleukin-12-deficient mice. Eur J Immunol 1996, 26:2933–2938. 34. Nakajima A, Seroogy CM, Sandora MR, et al.: Antigen-specific T cell-mediated gene therapy in collagen-induced arthritis. J Clin Invest 2001, 107:1293–1301. 35. Joosten LA, Lubberts E, Helsen MM, van den Berg WB: Dual role of IL-12 in early and late stages of murine collagen type II arthritis. J Immunol 1997, 159:4094–4102. 36. Fehniger TA, Caligiuri MA: Interleukin 15: biology and relevance to human disease. Blood 2001, 97:14–32. 37. Thurkow EW, van der Heijden IM, Breedveld FC, et al.: Increased expression of IL-15 in the synovium of patients with rheumatoid arthritis compared with patients with Yersinia-induced arthritis and osteoarthritis. J Pathol 1997, 181:444–450. 38. McInnes IB, al-Mughales J, Field M, et al.: The role of interleukin-15 in T-cell migration and activation in rheumatoid arthritis. Nat Med 1996, 2:175–182. 39. Ziolkowska M, Koc A, Luszczykiewicz G, et al.: High levels of IL-17 in rheumatoid arthritis patients: IL-15 triggers in vitro IL-17 production via cyclosporin A-sensitive mechanism. J Immunol 2000, 164:2832–2838. 40. McInnes IB, Leung BP, Sturrock RD, Field M, Liew FY: Interleukin-15 mediates T cell-dependent regulation of tumor necrosis factor-alpha production in rheumatoid arthritis. Nat Med 1997, 3:189–195. 41. Harada S, Yamamura M, Okamoto H, et al.: Production of interleukin-7 and interleukin-15 by fibroblast-like synoviocytes from patients with rheumatoid arthritis. Arthritis Rheum 1999, 42:1508–1516.

216

Rheumatoid Arthritis

42.• Ruchatz H, Leung BP, Wei XQ, McInnes IB, Liew FY: Soluble IL15 receptor alpha-chain administration prevents murine collagen-induced arthritis: a role for IL-15 in development of antigen-induced immunopathology. J Immunol 1998, 160:5654–5660. This paper presents data that demonstrate a pivotal role for interleukin (IL)-15 in the development of arthritis and suggest that antagonists to IL-15 may have therapeutic potential in rheumatic diseases. 43. Laan M, Cui ZH, Hoshino H, et al.: Neutrophil recruitment by human IL-17 via C-X-C chemokine release in the airways. J Immunol 1999, 162:2347–2352. 44. Schwarzenberger P, La Russa V, Miller A, et al.: IL-17 stimulates granulopoiesis in mice: use of an alternate, novel gene therapy-derived method for in vivo evaluation of cytokines. J Immunol 1998, 161:6383–6389. 45. Chabaud M, Durand JM, Buchs N, et al.: Human interleukin17: a T cell-derived proinflammatory cytokine produced by the rheumatoid synovium. Arthritis Rheum 1999, 42:963–970. 46. Honorati MC, Meliconi R, Pulsatelli L, et al.: High in vivo expression of interleukin-17 receptor in synovial endothelial cells and chondrocytes from arthritis patients. Rheumatology (Oxford) 2001, 40:522–527. 47.• Lubberts E, Joosten LA, van de Loo FA, et al.: Reduction of interleukin-17-induced inhibition of chondrocyte proteoglycan synthesis in intact murine articular cartilage by interleukin-4. Arthritis Rheum 2000, 43:1300–1306. This paper shows that blocking of endogenous interleukin (IL)-17 in CIA in mice results in suppression of arthritis, including a clear suppression of joint damage. Local overexpression of IL-17 promoted destructive arthritis. Neutralization of IL-1 had no effect on IL-17induced inflammation and joint damage, identifying an IL-1-independent role for IL-17. 48. Kong YY, Yoshida H, Sarosi I, et al.: OPGL is a key regulator of osteoclastogenesis, lymphocyte development and lymphnode organogenesis. Nature 1999, 397:315–323. 49. Lubberts E, Joosten LA, Oppers B, et al.: IL-1-independent role of IL-17 in synovial inflammation and joint destruction during collagen-induced arthritis. J Immunol 2001, 167:1004–1013. 50. Bush KA, Lenarczyk A, Portek I, et al.: Interleukin-17 in rheumatoid arthritis (RA): production by RA synovial membrane cultures and IL-17 receptor (IgG1) fusion protein treatment in rat adjuvant arthritis (AA) [abstract]. Arthritis Rheum 2001, 44:S113. 51. Chabaud M, Lubberts E, Joosten L, van Den BW, Miossec P: IL17 derived from juxta-articular bone and synovium contributes to joint degradation in rheumatoid arthritis. Arthritis Res 2001, 3:168–177. 52.• Chabaud M, Miossec P: The combination of tumor necrosis factor alpha blockade with interleukin-1 and interleukin-17 blockade is more effective for controlling synovial inflammation and bone resorption in an ex vivo model. Arthritis Rheum 2001, 44:1293–1303. The inhibitory effect of sTNFR on IL-6 production and collagen degradation in RA synovium and bone was increased in combination with sIL-17R and sIL-1RII. These results support the concept of combination therapy, which may increase the percentage of responding patients and the degree of the patient response. 53. Gracie JA, Forsey RJ, Chan WL, et al.: A proinflammatory role for IL-18 in rheumatoid arthritis. J Clin Invest 1999, 104:1393–1401. 54. Nakanishi K, Yoshimoto T, Tsutsui H, Okamura H: Interleukin18 is a unique cytokine that stimulates both Th1 and Th2 responses depending on its cytokine milieu. Cytokine Growth Factor Rev 2001, 12:53–72. 55.• Park CC, Morel JC, Amin MA, et al.: Evidence of IL-18 as a novel angiogenic mediator. J Immunol 2001, 167:1644–1653. A novel function of IL-18 as an angiogenic mediator is reported. This activity can be relevant for the pathogenesis of rheumatoid arthritis. 56. Leung BP, Culshaw S, Gracie JA, et al.: A role for IL-18 in neutrophil activation. J Immunol 2001, 167:2879–2886. 57. Olee T, Hashimoto S, Quach J, Lotz M: IL-18 is produced by articular chondrocytes and induces proinflammatory and catabolic responses. J Immunol 1999, 162:1096–1100.

58.

Horwood NJ, Udagawa N, Elliott J, et al.: Interleukin 18 inhibits osteoclast formation via T cell production of granulocyte macrophage colony-stimulating factor. J Clin Invest 1998, 101:595–603. 59. Leung BP, McInnes IB, Esfandiari E, Wei XQ, Liew FY: Combined effects of IL-12 and IL-18 on the induction of collageninduced arthritis. J Immunol 2000, 164:6495–6502. 60. Joosten LA, van de Loo FA, Lubberts E, et al.: An IFN-gammaindependent proinflammatory role of IL-18 in murine streptococcal cell wall arthritis. J Immunol 2000, 165:6553–6558. 61.• Wei XQ, Leung BP, Arthur HM, McInnes IB, Liew FY: Reduced incidence and severity of collagen-induced arthritis in mice lacking IL-18. J Immunol 2001, 166:517–521. The results of this paper provide definitive evidence that IL-18 plays a crucial role in the development and sustenance of arthritis. 62. Plater-Zyberk C, Joosten L, Helsen MM, et al.: IL-18 blockade is a potential disease-modifying therapy for rheumatoid arthritis. Arthritis Res 2001, 3:P092. 63. Song XY, Gu M, Jin WW, et al.: Plasmid DNA encoding transforming growth factor-beta1 suppresses chronic disease in a streptococcal cell wall-induced arthritis model. J Clin Invest 1998, 101:2615–2621. 64. Fava R, Olsen N, Keski-Oja J, et al.: Active and latent forms of transforming growth factor beta activity in synovial effusions. J Exp Med 1989, 169:291–296. 65. van den Berg WB: Joint inflammation and cartilage destruction may occur uncoupled. Springer Semin Immunopathol 1998, 20:149–164. 66. Bakker AC, van de Loo FA, van Beuningen HM, et al.: Overexpression of active TGF-beta-1 in the murine knee joint: evidence for synovial-layer-dependent chondro-osteophyte formation. Osteoarthritis Cartilage 2001, 9:128–136. 67. Buckley CD, Amft N, Bradfield PF, et al.: Persistent induction of the chemokine receptor CXCR4 by TGF-beta 1 on synovial T cells contributes to their accumulation within the rheumatoid synovium. J Immunol 2000, 165:3423–3429. 68. Akbar AN, Lord JM, Salmon M: IFN-alpha and IFN-beta: a link between immune memory and chronic inflammation. Immunol Today 2000, 21:337–342. 69. Triantaphyllopoulos KA, Williams RO, Tailor H, Chernajovsky Y: Amelioration of collagen-induced arthritis and suppression of interferon-gamma, interleukin 12, and tumor necrosis factor alpha production by interferon beta gene therapy. Arthritis Rheum 1999, 42:90–99. 70. van Holten J, Smeets TJ, Sattonnet-Roche P, et al.: The effects of interferon-beta (IFN-␤) treatment on synovial cytokine expression in collagen induced arthritis in DBA/1 mice [abstract]. Arthritis Rheum 2001, 44:S242. 71. Tak PP, Hart BA, Kraan MC, et al.: The effects of interferon beta treatment on arthritis. Rheumatology (Oxford) 1999, 38:362–369. 72. Sundel RP, Wallace CA, Zurakowski D: Pilot trial of interferonbeta-1a (Avonex) in JRA [abstract]. Arthritis Rheum 2001, 44:S272. 73. van Roon JAG, Lafeber FP, Bijlsma JW: Synergistic activity of interleukin-4 and interleukin-10 in suppression of inflammation and joint destruction in rheumatoid arthritis. Arthritis Rheum 2001, 44:3–12. 74. Woods JM, Katschke KJJ, Tokuhira M, et al.: Reduction of inflammatory cytokines and prostaglandin E2 by IL-13 gene therapy in rheumatoid arthritis synovium. J Immunol 2000, 165:2755–2763. 75. Bessis N, Boissier MC, Ferrara P, et al.: Attenuation of collageninduced arthritis in mice by treatment with vector cells engineered to secrete interleukin-13. Eur J Immunol 1996, 26:2399–2403. 76. Morita Y, Yang J, Gupta R, et al.: Dendritic cells genetically engineered to express IL-4 inhibit murine collagen-induced arthritis. J Clin Invest 2001, 107:1275–1284. 77. Boyle DL, Nguyen KH, Zhuang S, et al.: Intra-articular IL-4 gene therapy in arthritis: anti-inflammatory effect and enhanced th2 activity. Gene Ther 1999, 6:1911–1918.

Cytokines in Rheumatoid Arthritis • Vervoordeldonk and Tak

78.

79.

80.

Van den Bosch F, Russel A, Keystone EC, et al.: rHuIL-4 in subjects with active rheumatoid arthritis: a phase I dose escalating safety study. Arthritis Rheum 1998, 41:S56. Maini RN, Paulus H, Breedveld FC, et al.: rHuIL-10 in subjects with active rheumatoid arthritis: a phase I and cytokine response study. Arthritis Rheum 1997, 40:S224. Hermann JA, Hall MA, Maini RN, et al.: Important immunoregulatory role of interleukin-11 in the inflammatory process in rheumatoid arthritis. Arthritis Rheum 1998, 41:1388–1397.

81.

82.

217

Walmsley M, Marinova-Mutafchieva L, Butler DM, Feldmann M: An anti-inflammatory role for interleukin-11 in established murine collagen-induced arthritis. Immunology 1998, 94:31–37. Moreland LW, Gugliotti R, King K, et al.: Results of a phase-I/II randomized, masked, placebo-controlled trial of recombinant human interleukin-11 (rHIL-11) in the treatment of subjects with active rheumatoid arthritis. Arthritis Res 2001, 3:247–252.