Bypassing the antigen to control rheumatoid arthritis

Cyclosporine A inhibits IL-15-induced IL-17 production in CD4+ T cells via down-regulation of PI3K/Akt and NF-kappaB

Cyclosporine A (CSA) has various biological effects on T cells, including inhibition of interleukin (IL)-15-induced IL-17 production in CD4+ T cells from patients with rheumatoid arthritis (RA). However, the mechanism underlying this effect is not fully understood. Here, we tried to investigate the mechanism of CSA to inhibit IL-17 production induced by IL-15 in CD4+ T cells. Synovial fluid and serum levels of IL-15 and IL-17 were determined by ELISA. CD4+ T cells from RA patients were treated with IL-15 in the presence of CSA or several signal inhibitors. The concentration of IL-17 in culture supernatants was measured by ELISA and IL-17 mRNA expression was determined by RT-PCR. NF-kappaB binding activity for IL-17 transcription was assessed by electrophoretic mobility shift assay. IL-15 induced IL-17 production by CD4+ T cells in dose- and time-dependent manner. IL-15-stimulated IL-17 production and mRNA expression were inhibited by CSA in CD4+ T cells. Moreover PI3K/Akt inhibitor, NF-kappaB inhibitor, and FK506 significantly inhibited IL-15-induced IL-17 production in CD4+ T cells. Inhibition studies revealed the requirement of PI3K/Akt and NF-kappaB signal pathway for IL-15-induced IL-17 production. CSA down-regulated the phosphorylation of Akt and IkappaB. CSA inhibited binding of NF-kappaB to IL-17 promoter. The inhibitory effect of CSA on IL-15 induced IL-17 production partially depended on the increase in IL-10, since neutralizing anti-IL-10 antibodies were able to partially reverse this inhibition. CSA inhibits IL-17 production by CD4+ T cells and this effect is mediated by IL-15-activated NF-kappaB pathway in CD4+ T cells, which is possible mechanism of CSA in treating RA as NF-kappaB targeting strategy.

Selective elimination of synovial inflammatory macrophages in rheumatoid arthritis by an Fcgamma receptor I-directed immunotoxin

OBJECTIVE

To determine whether monocyte/macrophages from rheumatoid arthritis (RA) patients can be selectively eliminated by a toxin-conjugated antibody CD64-ricin A (CD64-RiA) directed toward the high-affinity receptor for IgG (FcgammaRI), exploiting the capacity of FcgammaRI to efficiently endocytose antibody which it has bound.

METHODS

Mononuclear cells from peripheral blood (PB) and synovial fluid (SF) obtained from RA patients were cultured in the presence of CD64-RiA. Cell death of monocyte/macrophages was measured by phenotypic changes (light-scatter patterns and CD14 and FcgammaRI expression) and apoptosis (nuclear DNA fragmentation). We then tested whether CD64-RiA-induced cell death of macrophages affected their capacity to stimulate antigen-induced lymphocyte proliferation and to secrete cytokines. Additionally, the capacity of CD64-RiA to inhibit proinflammatory activity and cartilage degradation by RA synovial tissue explants was evaluated.

RESULTS

Inflammatory macrophages from RA SF expressed elevated levels of FcgammaRI and were selectively eliminated by CD64-RiA via apoptotic cell death. Monocyte/macrophages from RA PB, which had lower levels of FcgammaRI expression, were much less affected. Induction of SF macrophage apoptosis was associated with efficient inhibition of antigen-induced lymphocyte proliferation and a reduction in tumor necrosis factor alpha (TNFalpha) release. Consistent with these effects on SF macrophages, CD64-RiA also inhibited TNFalpha production, interleukin-1beta production, and cartilage-degrading activity of RA synovial tissue explants.

CONCLUSION

Together, these data underscore the crucial role of synovial macrophages in RA joint inflammation and indicate that selective elimination of these cells through FcgammaRI-directed immunotoxins could be a novel approach to the treatment of RA.

Interleukin 7 stimulates tumour necrosis factor alpha and Th1 cytokine production in joints of patients with rheumatoid arthritis

BACKGROUND

A large number of activated T cells are found in the joints of patients with rheumatoid arthritis (RA). Interleukin 7 (IL7), a T cell growth factor and a regulator of Th1 and Th2 cytokine production, is produced by synoviocytes from patients with RA.

OBJECTIVE

To investigate the effect on proinflammatory cytokine production of synovial fluid mononuclear cells (SFMC) and the mechanism by which IL7 influences CD4+ T cell activity in patients with RA.

METHODS

In a cross sectional group of patients with RA, IL7 levels were compared with those of healthy controls and related to disease activity. The effect of IL7 on cytokine production was tested by RA SFMC and on SF CD4+ T cells in the presence of mononuclear cells (MC). Production of tumour necrosis factor alpha (TNF alpha), IL1 beta, interferon gamma (IFN gamma), and IL4 was measured by enzyme linked immunosorbent assay (ELISA) and by single cell FACS analysis. Expression of the IL7 receptor alpha chain on CD4+ T cells (essential for IL7 signalling) was assessed. Direct effects of IL7 on isolated synovial fluid (SF) CD4+ T cells were studied by cytokine analysis. By neutralisation of IL12 in MC cultures, indirect effects of IL7 on T cells through accessory cells were studied.

RESULTS

IL7 serum levels were higher in patients with RA than in healthy controls and correlated positively with C reactive protein levels. IL7 stimulated TNFalpha production by SFMC and very potently stimulated IFN gamma and TNF alpha production by SF CD4+ T cells. These effects were probably mediated through the IL7 receptor alpha chain, which was abundantly expressed on SF CD4+ T cells. Besides the direct stimulation of T cell cytokine production by IL7, its action was partly dependent on IL12, indicating that IL7 also stimulates accessory cell function, leading to T cell activation.

CONCLUSION

IL7 stimulates proinflammatory cytokine production of intra-articular CD4+ T cells and accessory cells from patients with RA. The correlation with measures of disease activity indicates that IL7 might substantially contribute to the perpetuation of Th1 and TNF alpha mediated proinflammatory responses in patients with RA.

Differentiation of naive CD4+ T cells towards T helper 2 cells is not impaired in rheumatoid arthritis patients

An impaired differentiation of naive CD4+ T cells towards Th2 cells may contribute to the chronic tissue-destructive T-cell activity in rheumatoid arthritis (RA). The differentiation of naive CD4+ T cells into memory Th2 cells by IL-7 in comparison with that by IL-4 was studied in RA patients and in healthy controls. Naive CD4+ T cells from peripheral blood were differentiated by CD3/CD28 costimulation in the absence of or in the presence of IL-7 and/or IL-4. The production of IFN-gamma and IL-4 was measured by ELISA and by single-cell FACS analysis to indicate Th1 and Th2 cell activity. CD3/CD28 costimulation and IL-7 were early inducers of IL-4 production, but primarily stimulated IFN-gamma production. In contrast, in short-term cultures exogenously added IL-4 did not prime for IL-4 production but suppressed IL-7-induced IFN-gamma production. Upon long-term stimulation of naive CD4+ T cells, IFN-gamma production was differentially regulated by IL-7 and IL-4, but IL-4 production was increased by both IL-7 and IL-4. IL-7 and IL-4 additively induced polarization towards a Th2 phenotype. This susceptibility of naive CD4+ T cells to become Th2 cells upon culture with IL-7 and IL-4 was increased in RA patients compared with that in healthy controls. These findings demonstrate that, in RA patients, differentiation of naive CD4+ T cells towards a Th2 phenotype by CD3/CD28 costimulation, IL-7 and IL-4 is not impaired. The perpetuation of arthritogenic T-cell activity in RA therefore seems not to be the result of intrinsic defects of naive CD4+ T cells to develop towards suppressive memory Th2 cells.

Rapid onset of cutaneous squamous cell carcinoma in patients with rheumatoid arthritis after starting tumor necrosis factor alpha receptor IgG1-Fc fusion complex therapy

Tumor necrosis factor alpha (TNF-alpha) is now believed to be a major contributor to the pathogenesis of the synovitis and joint destruction in rheumatoid arthritis. Etanercept is a recombinant human TNF-alpha receptor Fc fusion protein consisting of a dimer of the extracellular portion of two p75 TNF-alpha receptors fused to the Fc portion of human IgG1. Etanercept produces significant dose-dependent improvements in disease activity. We describe 7 patients who experienced 1 or more squamous cell carcinomas that showed rapid growth and arose over a 2- to 4-month period of etanercept therapy. Soluble TNF-alpha receptor therapy through inhibition of a T(H)1 cytokine pattern and inhibition of the direct and indirect cytotoxic effects of TNF-alpha may initially decrease mechanisms for controlling subclinical tumors and may contribute to the histologic features seen within these tumors. However, prolonged TNF-alpha inhibition may have some antitumor effects.

Switch in chemokine receptor phenotype on memory T cells without a change in the cytokine phenotype

Th1 and Th2 cells as defined by their cytokine profile are associated with the expression of the chemokine receptors CCR5 and CCR3, respectively. In committed human memory Th1 cells the cytokine profile is irreversibly expressed. However, it is not known if the chemokine receptor phenotypes of Th1 and Th2 cells are permanently associated to the cytokine profile or if it can be changed. To analyze the possibility of inducing a switch in chemokine receptor phenotype on memory Th cells we used differentiated memory Th cells isolated from synovial tissue (ST) samples of patients with rheumatoid arthritis (RA). Freshly isolated T cells, T-cell lines and T-cell clones from these tissues were manipulated with Th1 (interleukin (IL)-12 + anti IL-4) or Th2 (IL-4 + anti IL-12) inducing conditions. The surface expression of CCR5 and CCR3 was analyzed by flowcytometry and interferon (IFN)-gamma and IL-4 production by ELISA. A Th1-inducing cytokine environment increased the expression of CCR5 in Th1 cells and induced the expression of CCR5 in Th2 cells as compared to culture condition with only IL-2. Induction of CCR5 expression on Th2 clones was associated with secretion of some IFN-gamma. Moreover, the Th2-associated chemokine receptor CCR3 could be expressed on both Th1-dominant cell lines, and clones of Th1 and Th0 type after culture conditions with IL-4. This expression of CCR3 was associated with a reduced IFN-gamma production, but no IL-4 production could be induced. The IL-4-treated Th1 clones had a reduced migratory capacity against chemokines produced by ST cells compared to nonmanipulated T-cell clones. In contrast, the same IL-12-treated Th1 clones showed an increased migratory potential. Induction of the Th2-associated marker CCR3 on memory Th1 cells demonstrates that a change in chemokine receptor phenotype related to the Th2 type can be induced on terminally differentiated Th1 cells, without a change in the cytokine profile.

Therapeutic relevance of altered cytokine expression

Cytokines and their receptors have numerous physiological functions. Altered concentrations of these mediators are associated with various afflictions. For example, over-expression of cytokines has been associated with altered drug concentrations and activity. Greater concentrations of cardiovascular drugs have been observed in humans and laboratory animals with various types of inflammatory disorders compared to healthy controls. Interestingly, the observed higher concentrations of drugs such as propranolol and verapamil have not been associated with increased effects. Indeed, reduced response to these cardiovascular drugs is observed, suggestive of cytokine-mediated downregulation of receptors. Increased cytokine concentrations have also been associated with decreased response to drugs used in treatment of other disorders such as AIDS, asthma and psychiatric diseases. This reduced response to drug in the presence of altered cytokine concentrations is especially relevant to the elderly population which has a greater incidence of multiple diseases and elevated concentrations of various cytokines compared to younger individuals. Furthermore, inflammatory conditions and their accompanied increased over-expression of cytokines are suggested to be the main determinants of therapeutic failure in myocardial infarction and angina. Therefore, altered cytokine concentrations may influence therapeutic outcomes of pharmacotherapy and result in treatment failure.

Treatment of rheumatoid arthritis: etanercept a recent advance

PURPOSE

To review the specific mechanism of action of biologic response modifiers and help clinicians place these new drugs in the context of established therapies for rheumatoid arthritis (RA).

DATA SOURCES

Review of scientific literature, including all the clinical trials for these drugs.

CONCLUSIONS

Biologic response modifiers target key inflammatory events involved in joint destruction. They have the potential to revolutionize the management of RA.

IMPLICATIONS FOR PRACTICE

Referral to a rheumatologist should be strongly considered as soon as the diagnosis of RA is made. Early referral to a specialist has been associated with improved health status for patients with RA due to early and aggressive therapy with these new agents.

Changes in the Th1 or Th2 cytokine dominance in the synovium of rheumatoid arthritis (RA): a kinetic study of the Th subsets in one unusual RA patient

OBJECTIVE

To perform a kinetic study of the Th1/Th2 balance in the rheumatoid arthritis (RA) synovium.

METHODS

Three different synovial tissue (ST) samples were obtained from one patient with erosive RA. The characterization of Th1 and Th2 responses was performed by interferon-gamma and interleukin-4 measurements and by expression of the chemokine receptors CCR5 and CCR3. Measurements of secreted and surface immunoglobulin determined the types of B cells.

RESULTS

The first ST sample yielded 31 CD4+ T cell clones which showed an unusual Th2 dominant pattern in the inflamed synovium. The Th2 response was associated with predominantly synovial IgG B cells, and a predominantly Th1 profile in the peripheral blood. In contrast, ST samples obtained 2 and 2.5 yr later displayed first a Th0 and thereafter a Th1 profile, and the synovial B cell response was predominantly of IgM type. The T cell lines from the Th1/Th0 tissues expressed the Th1 marker CCR5 but not CCR3, while the T cells from the Th2 tissue expressed the Th2 marker CCR3 and no CCR5.

CONCLUSION

These results demonstrate that a predominantly Th2 response can be associated with active erosive RA. However, the Th2 profile was not permanent and changed into a Th0 and thereafter a Th1 profile.

Successful treatment of collagen-induced arthritis in mice with a hydroalcohol extract of seeds of Pterodon pubescens

The antiarthritic effect of a hydroalcohol extract of Pterodon pubescens (HEPp) seeds was tested using collagen-induced arthritis (CIA) in DBA1/J mice treated with daily oral doses of HEPp in different schedules. The preventive treatment significantly reduced both the arthritic index (AI) and the CIA incidence. Using a therapeutic protocol, only the lower dose of HEPp induced a decrease in both parameters. These results provide a scientific foundation for the popular use of Pp seed infusions in rheumatoid arthritis (RA) treatment.

The preventive effects of incomplete Freund's adjuvant and other vehicles on the development of adjuvant-induced arthritis in Lewis rats

The present study showed a novel finding that the development of adjuvant-induced arthritis (AA) in Lewis rats was completely prevented by incomplete Freund's adjuvant (IFA) injected 21 or 28 days before complete Freund's adjuvant (CFA) challenge. Hexadecane also completely prevented AA and squalane, methyl oleate and pristane moderately prevented AA, though pristane by itself induced mild arthritis in two out of five rats. Concanavalin A-stimulated lymph node cells (LNCs) isolated from AA rats were able to adoptively transfer the severe polyarthritis to all the naive recipients or even to the IFA pretreated recipients with earlier onset and more rapid progression than those of AA. The LNCs from the donors who had been pretreated with IFA and subsequently challenged with CFA could induce mild arthritis in only two out of eight naive recipients, whereas all the recipients who were challenged with CFA immediately after intravenous injection of these LNCs developed significantly less severe arthritis. However, the LNCs from IFA-pretreated donors failed to prevent AA. According to the T helper type 1 (Th1)/Th2 paradigm, it was suggested that the adjuvant-active vehicles such as IFA, hexadecane, squalane, methyl oleate and pristane, can affect and deviate the Th1/Th2 balance of immune responses in host. CFA could promote the propagation of Th2 cells rather than Th1 cells in these vehicle-pretreated rats through as yet undetermined mechanisms, eventually resulting in the prevention of AA. Finally, we discussed a regulatory role of adjuvant vehicles for induction and suppression of AA.

Dendritic cells: the driving force behind autoimmunity in rheumatoid arthritis?

Dendritic cells (DC) are likely to play a significant role in immune-mediated diseases such as autoimmunity and allergy. To date there are few treatments capable of inducing permanent remission in rheumatoid arthritis (RA) and elucidation of the role of DC may provide specific strategies for disease intervention. Dendritic cells have proven to be powerful tools for immunotherapy and investigations are under way to determine their clinical efficacy in transplantation and viral and tumour immunotherapy. The present review will focus on the current view of DC and their role in autoimmunity, in particular RA. Two possible roles for DC in the pathogenesis of RA will be proposed, based on recent advances in the field.

Inflammatory arthritic process, iridocyclitis and immune response to articular and ocular antigens in Wistar rats injected with T. gondii trophozoites

The present study deals with the potential role of T. gondii in inducing an arthritic inflammatory process. Wistar rats were injected subcutaneously (sc) into the right footpad with viable T. gondii trophozoites emulsified in incomplete Freund's adjuvant (IFA). The control group was injected with IFA. All parasite-injected animals developed a local inflammatory process characterized by hind limb swelling and marked restriction of ankle motility approximately 25 days after injection. Histopathogical studies of the joints, carried out 90 days after injection, revealed intense mononuclear infiltration, proliferation of granulation tissue, giant cells and necrosis in the synovia of 90% of T. gondii-injected rats. Strikingly, 40% (4/10) of the parasite-injected animals developed iridocyclitis, which was characterized by intense mononuclear infiltration around the iris-ciliary microvasculature in two animals and a slightly pronounced infiltrate of polymorphonuclear and mononuclear cells in two other animals. Antibodies to soluble T. gondii antigens (STAg) were detected in all parasite-injected rats. Antibodies against articular and ocular antigens such as proteoglycans, type II collagen, retinal S antigen and iris antigens were detected by ELISA in 40, 80, 70 and 70% of T. gondii -injected animals, respectively. Control animals injected with IFA failed to develop any articular or ocular process or humoral immune response. The present study demonstrated that footpad sc injection of Wistar rats with viable T. gondii trophozoites was able to induce a localized inflammatory arthritic process which, in some of the animals, was accompanied by iridocyclitis and immune response against articular and ocular components.

Protection against cartilage and bone destruction by systemic interleukin-4 treatment in established murine type II collagen-induced arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is associated with an increased production of a range of cytokines including tumour necrosis factor (TNF)-alpha and interleukin (IL)-1, which display potent proinflammatory actions that are thought to contribute to the pathogenesis of the disease. Although TNF-alpha seems to be the major cytokine in the inflammatory process, IL-1 is the key mediator with regard to cartilage and bone destruction. Apart from direct blockage of IL-1/TNF, regulation can be exerted at the level of modulatory cytokines such as IL-1 and IL-10. IL-4 is a pleiotropic T-cell derived cytokine that can exert either suppressive or stimulatory effects on different cell types, and was originally identified as a B-cell growth factor and regulator of humoral immune pathways. IL-4 is produced by activated CD4+T cells and it promotes the maturation of TH2 cells. IL-4 stimulates proliferation, differentiation and activation of several cell types, including fibroblasts, endothelial cells and epithelial cells. IL-4 is also known to be a potent anti-inflammatory cytokine that acts by inhibiting the synthesis of proinflammatory cytokines such as IL-1, TNF-alpha, IL-6, IL-8 and IL-12 by macrophages and monocytes. Moreover, IL-4 stimulates the synthesis of several cytokine inhibitors such as interleukin-1 receptor antagonist (IL-1Ra), soluble IL-1-receptor type II and TNF receptors IL-4 suppresses metalloproteinase production and stimulates tissue inhibitor of metalloproteinase-1 production in human mononuclear phagocytes and cartilage explants, indicating a protective effect of IL-4 towards extracellular matrix degradation. Furthermore, IL-4 inhibits both osteoclast activity and survival, and thereby blocks bone resorption in vitro. Of great importance is that IL-4 could not be detected in synovial fluid or in tissues. This absence of IL-4 in the joint probably contributes to the disturbance in the Th1/Th2 balance in chronic RA. Collagen-induced arthritis (CIA) is a widely used model of arthritis that displays several features of human RA. Recently it was demonstrated that the onset of CIA is under stringent control of IL-4 and IL-10. Furthermore, it was demonstrated that exposure to IL-4 during the immunization stage reduced onset and severity of CIA. However, after cessation of IL-4 treatment disease expression increased to control values.

AIMS

Because it was reported that IL-4 suppresses several proinflammatory cytokines and matrix degrading enzymes and upregulates inhibitors of both cytokines and catabolic enzymes, we investigated the tissue protective effect of systemic IL-4 treatment using established murine CIA as a model. Potential synergy of low dosages of anti-inflammatory glucocorticosteroids and IL-4 was also evaluated.

METHODS

DBA-1J/Bom mice were immunized with bovine type II collagen and boosted at day 21. Mice with established CIA were selected at day 28 after immunization and treated for days with IL-4, prednisolone, or combinations of prednisolone and IL-4. Arthritis score was monitored visually. Joint pathology was evaluated by histology, radiology and serum cartilage oligomeric matrix protein (COMP). In addition, serum levels of IL-1Ra and anticollagen antibodies were determined.

RESULTS

Treatment of established CIA with IL-4 (1microgram/day) resulted in suppression of disease activity as depicted in Figure 1. Of great interest is that, although 1 microgram/day IL-4 had only a moderate effect on the inflammatory component of the disease activity, it strongly reduced cartilage pathology, as determined by histological examination (Fig. 1). Moreover, serum COMP levels were significantly reduced, confirming decreased cartilage involvement. In addition, both histological and radiological analysis showed that bone destruction was prevented (Fig. 1). Systemic IL-4 administration increased serum IL-1Ra levels and reduced anticollagen type II antibody levels. Treatment with low-dose IL-4 (0.1 microgram/day) was ineffective in suppressing disease score, serum COMP or joint destruction. Synergistic suppression of both arthritis severity and COMP levels was noted when low-dose IL-4 was combined with prednisolone (0.05 mg/kg/day), however, which in itself was not effective.

DISCUSSION

In the present study, we demonstrate that systemic IL-4 treatment ameliorates disease progression of established CIA. Although clinical disease progression of established CIA. Although clinical disease progression was only arrested and not reversed, clear protection against cartilage and bone destruction was noted. This is in accord with findings in both human RA and animal models of RA that show that inflammation and tissue destruction sometimes are uncoupled processes. Of great importance is that, although inflammation was still present, strong reduction in serum COMP was found after exposure to IL-4. This indicated that serum COMP levels reflected cartilage damage, although a limited contribution of the inflamed synovium cannot be excluded. Increased serum IL-1Ra level (twofold) was found after systemic treatment with IL-4, but it is not likely that this could explain the suppression of CIA. We and others have reported that high dosages of IL-1Ra are needed for marked suppression of CIA. As reported previously, lower dosages of IL-4 did not reduce clinical disease severity of established CIA. Of importance is that combined treatment of low dosages of IL-4 and IL-10 appeared to have more potent anti-inflammatory effects, and markedly protected against cartilage destruction. Improved anti-inflammatory effect was achieved with IL-4/prednisolone treatment. In addition, synergistic effects were found for the reduction of cartilage and bone destruction. This indicates that systemic IL-4/prednisolone treatment may provide a cartilage and bone protective therapy for human RA.

Biologic agents and immunotherapy in rheumatoid arthritis. Progress and perspective

Advances in our understanding of rheumatoid synovitis have been coupled with increasingly refined methods from biotechnology to produce promising therapeutic agents. Monoclonal antibodies (MoAbs), recombinant cytokines, cytokine receptor fusion proteins and other biologics have been elevated from the status of novel reagents applied in phase I toxicity trials to, in some cases, substantially evaluated and validated tools awaiting federal regulatory approval. Biologic agents will soon be released for the treatment of patients with RA. We review some of the most promising preclinical work that supports a position of optimism regarding the future of RA. We also speculate on the potential role for biologics in future management of patients with RA.

Cytokines in thyroid eye disease: potential for anticytokine therapy

Interactions between between orbital fibroblasts and immunocompetent cells that infiltrate or reside within the orbit are thought to be important in the pathogenesis of thyroid eye disease (TED). These interactions are mediated primarily by cytokines; interferon-gamma, tumor necrosis factor-alpha, interleukin-1alpha and leukoregulin are of particular interest in this regard. These mediators induce or enhance the in vitro expression of immunomodulatory proteins in orbital fibroblasts, and stimulate proliferative and metabolic activities of these cells. The stimulation by particular cytokines of glycosaminoglycan synthesis in orbital fibroblasts is an important factor in the development of the clinical disease. A similarly important pathophysiological role for cytokines has been defined in rheumatoid arthritis. In this disease, the chronic erosive changes in the cartilage and bone of the joints result from cytokine-stimulated production of collegenases and other neutral proteases by synovial cells and articular chondrocytes. Advances in the understanding of the pathogenesis of rheumatologic joint disease has led to treatment trials aimed at immune-modulation, including trials of anticytokine therapy. Lessons learned in early clinical trials using these biological therapies in the treatment of rheumatoid arthritis can be applied to studies of similar agents in the treatment of TED.

Glucocorticoids and immune function: unknown dimensions and new frontiers

Despite the importance of glucocorticoids (GCs) to modern medicine, the physiological role of endogenous corticosteroids in immunomodulation is poorly understood. This article discusses evidence suggesting that endogenous GCs not only suppress but also direct and enhance immune functions. These often overlooked actions might well be more important than the inhibitory functions during host defence and the maintenance of homeostasis.

Cytokine-induced autoimmune disorders

Cytokines are now commonly used in the treatment of many conditions, especially cancer, haematological malignancies and chronic viral hepatitis. With some of these cytokines, clinical induction and/or exacerbation of autoimmune manifestations have been observed. This has been the case with interferon-alpha and interferon-gamma, interleukin-2 and some colony-stimulating factors. All known biological and clinical autoimmune features have been observed but thyroid abnormalities have been particularly frequent. Some of these manifestations appear to be related to the effect of these exogenous cytokines on the T helper cell (TH) 1/TH2-cytokine balance and the regulatory properties of these cells. Patients with a history of underlying autoimmune disease or baseline serological abnormalities should be monitored for autoimmunity when treated with certain TH1 or TH2-inducing cytokines.

Interleukin-15 mediates T cell-dependent regulation of tumor necrosis factor-alpha production in rheumatoid arthritis

Tumor necrosis factor-alpha occupies a central role in rheumatoid arthritis (RA) pathogenesis. We now report that interleukin-15 (IL-15) can induce TNF-alpha production in RA through activation of synovial T cells. Peripheral blood (PB) T cells activated by IL-15 induced significant TNF-alpha production by macrophages via a cell-contact-dependent mechanism. Freshly isolated RA synovial T cells possessed similar capability, and in vitro, IL-15 was necessary to maintain this activity. IL-15 also induced direct TNF-alpha production by synovial T cells. In contrast, IL-2 induced significantly lower TNF-alpha production in either cell-contact-dependent or direct culture, and IL-8 and MIP-1 alpha were ineffective. Antibodies against CD69, LFA-1 or ICAM-1 significantly inhibited the ability of T cells to activate macrophages by cell contact.