Results of a multicenter placebo-controlled double-blind randomized phase III clinical study of treatment of rheumatoid arthritis with recombinant interferon-gamma

Synovial Tissue Insights into Heterogeneity of Rheumatoid Arthritis

PURPOSE OF REVIEW

Rheumatoid arthritis is one of the most common rheumatic and autoimmune diseases. While it can affect many different organ systems, RA primarily involves inflammation in the synovium, the tissue that lines joints. Patients with RA exhibit significant clinical heterogeneity in terms of presence or absence of autoantibodies, degree of permanent deformities, and most importantly, treatment response. These clinical characteristics point to heterogeneity in the cellular and molecular pathogenesis of RA, an area that several recent studies have begun to address.

RECENT FINDINGS

Single-cell RNA-sequencing initiatives and deeper focused studies have revealed several RA-associated cell populations in synovial tissues, including peripheral helper T cells, autoimmunity-associated B cells (ABCs), and NOTCH3+ sublining fibroblasts. Recent large transcriptional studies and translational clinical trials present frameworks to capture cellular and molecular heterogeneity in RA synovium. Technological developments, such as spatial transcriptomics and machine learning, promise to further elucidate the different types of RA synovitis and the biological mechanisms that characterize them, key elements of precision medicine to optimize patient care and outcomes in RA. This review recaps the findings of those recent studies and puts our current knowledge and future challenges into scientific and clinical perspective.

Positive and negative cooperativity of TNF and Interferon-γ in regulating synovial fibroblast function and B cell survival in fibroblast/B cell co-cultures

Synovial fibroblasts (SF) were reported to produce B cell activating factor (BAFF) in response to stimulation with interferon-γ (IFN-γ) or tumor necrosis factor (TNF). However, the influence of these pro-inflammatory cytokines on other receptors/ligands of the TNF superfamily or associated cytokine receptors in SF has not been investigated yet. Here we show the differential regulation of BAFF (CD257), Fn14 (CD266), TACI (CD267), BAFF-R (CD268), BCMA (CD269), CD40 ligand (CD40L, CD154), IFN-γR (CD119), Leptin receptor (ObR, CD295), VCAM-1 (CD106) and membrane TGF-β in isolated SF and the impact of IFN-γ/TNF co-incubation on proliferation, IL-6 and IL-8 production. In addition, the impact of differentially stimulated SF on B cell survival in co-cultures was assessed. Surface cytokines and cytokine receptors were detected by flow cytometry. Soluble cytokine receptors and cytokines were quantified by ELISA. Proliferation was assessed by cell titer blue. Murine B cell survival in fibroblast/ B cell co-cultures was determined by annexin V/propidium iodide staining and flow cytometry. IFN-γ together with TNF synergistically and significantly increased the cell surface levels of BAFF, Fn14, TACI, BAFF-R, BCMA, CD40L, ObR and IFN-γR in rheumatoid arthritis SF after 72 h incubation. Soluble BAFF was only induced by IFN-γ and inhibited by TNF. Addition of TWEAK had no influence on proliferation or IL-8 production but decreased TNF-induced IL-6 production, whereas APRIL, BAFF and leptin did not modulate TNF or TNF/IFN-γ-induced proliferation or cytokine production. Proliferation was increased by TNF and further enhanced by the addition of IFN-γ. In co-culture experiments, SF stimulated with TNF/IFN but not TNF or IFN-γ alone increased shedding of VCAM-1 and expression of membrane TGFβ, which was associated with reduced survival of murine B cells. IFN-γ and TNF regulate the expression of TNF family member cytokines and associated receptors. Ligation of IFN-γR and Fn14 under pro-inflammatory conditions modulated IL-6/IL-8 production and proliferation. In B cell/SF co-cultures, the combination of TNF/IFN reduced B cell survival possibly via enhanced VCAM-1 shedding and/or increased TGF-β production. IFN-γ is necessary for the observed effects on B cell survival and SF cytokine production and emphasizes its anti-inflammatory role in rheumatoid arthritis.

Synovial Tissue Inflammation Mediated by Autoimmune T Cells

In rheumatoid arthritis (RA), various hematopoietic and non-hematopoietic cells present in the synovial tissue secrete numerous inflammatory mediators including pro-inflammatory cytokines critical for the induction of chronic joint inflammation and bone destruction. Fibroblast-like synoviocytes (FLSs) in the non-hematopoietic cell compartment are key inflammatory cells activated in inflamed joints and driving the disease; yet how synovial tissue inflammation is modulated by autoimmune T cells is not fully understood. In this review, mainly based on recent findings with a mouse model of spontaneous autoimmune arthritis, we discuss the mechanism of Th17-mediated synovial tissue inflammation; that is, what environmental stimuli and arthritogenic self-antigens trigger arthritis, how arthritogenic T cells initiate joint inflammation by stimulating FLSs, and how the cellular sources of GM-CSF from lymphoid and tissue stromal cells in the synovium contribute to the development of arthritis. We also highlight possible plasticity of Th17 cells toward pathogenic GM-CSF producers, and the functional instability of regulatory T cells under inflammatory conditions in RA joints.

Interferon-Gamma-Mediated Osteoimmunology

Osteoimmunology is the interdiscipline that focuses on the relationship between the skeletal and immune systems. They are interconnected by shared signal pathways and cytokines. Interferon-gamma (IFN-γ) plays important roles in immune responses and bone metabolism. IFN-γ enhances macrophage activation and antigen presentation. It regulates antiviral and antibacterial immunity as well as signal transduction. IFN-γ can promote osteoblast differentiation and inhibit bone marrow adipocyte formation. IFN-γ plays dual role in osteoclasts depending on its stage. Furthermore, IFN-γ is an important pathogenetic factor in some immune-mediated bone diseases including rheumatoid arthritis, postmenopausal osteoporosis, and acquired immunodeficiency syndrome. This review will discuss the contradictory findings of IFN-γ in osteoimmunology and its clinical application potential.

The tolerogenic role of IFN-γ

Due to its extremely pleiotropic nature, the complex effects of IFN-γ exerted both on immune and non-immune cell types still remain only partially understood. The longstanding view of IFN-γ as being a predominantly inflammatory cytokine is constantly challenged by increasing demonstrations of its direct or indirect regulatory roles. Interferon-γ can exert tolerogenic effects on both innate and adaptive immune cell types, promoting tolerance of various antigen-presenting cells, and augmenting function and differentiation of regulatory T cells, respectively. Its capacity to induce IDO-competence is not limited to immune cells but extends to other cell types such as mesenchymal stem cells, epithelial cells, and tumors. The pro-inflammatory role of IFN-γ in tumor immune surveillance can backfire by directly inducing inhibitory molecule expression, such as PDL-1, on tumor cells. With increasing knowledge regarding the role of different helper T cell subsets in certain autoimmune diseases, the once contradictory observations of disease attenuation by IFN-γ can now be explained by its opposing interplay with other effector cytokines, particularly IL-17. The paradoxically immunosuppressive role of IFN-γ is also becoming evident in the transplantation setting, and graft-versus-host-disease. In the present review, we will discuss the latest findings that help to elucidate this dual role of IFN-γ at a cellular level, and in various pathophysiological states.

Immunomodulation of autoimmune arthritis by pro-inflammatory cytokines

Pro-inflammatory cytokines promote autoimmune inflammation and tissue damage, while anti-inflammatory cytokines help resolve inflammation and facilitate tissue repair. Over the past few decades, this general feature of cytokine-mediated events has offered a broad framework to comprehend the pathogenesis of autoimmune and other immune-mediated diseases, and to successfully develop therapeutic approaches for diseases such as rheumatoid arthritis (RA). Anti-tumor necrosis factor-α (TNF-α) therapy is a testimony in support of this endeavor. However, many patients with RA fail to respond to this or other biologics, and some patients may suffer unexpected aggravation of arthritic inflammation or other autoimmune effects. These observations combined with rapid advancements in immunology in regard to newer cytokines and T cell subsets have enforced a re-evaluation of the perceived pathogenic attribute of the pro-inflammatory cytokines. Studies conducted by others and us in experimental models of arthritis involving direct administration of IFN-γ or TNF-α; in vivo neutralization of the cytokine; the use of animals deficient in the cytokine or its receptor; and the impact of the cytokine or anti-cytokine therapy on defined T cell subsets have revealed paradoxical anti-inflammatory and immunoregulatory attributes of these two cytokines. Similar studies in other models of autoimmunity as well as limited studies in arthritis patients have also unveiled the disease-protective effects of these pro-inflammatory cytokines. A major mechanism in this regard is the altered balance between the pathogenic T helper 17 (Th17) and protective T regulatory (Treg) cells in favor of the latter. However, it is essential to consider that this aspect of the pro-inflammatory cytokines is context-dependent such that the dose and timing of intervention, the experimental model of the disease under study, and the differences in individual responsiveness can influence the final outcomes. Nevertheless, the realization that pro-inflammatory cytokines can also be immunoregulatory offers a new perspective in fully understanding the pathogenesis of autoimmune diseases and in designing better therapies for controlling them.

Interferon-stimulated gene 20-kDa protein (ISG20) in infection and disease: Review and outlook

Interferon-stimulated exonuclease gene 20 (ISG20) is an RNA exonuclease in the yeast RNA exonuclease 4 homolog (REX4) subfamily and the DEDDh exonuclease family, and this gene codes for a 20-kDa protein. Those exonucleases are involved in cleaving single-stranded RNA and DNA. ISG20 is also referred to as HEM45 (HeLa estrogen-modulated, band 45). Expression of ISG20 can be induced or regulated by both type I and II interferons (IFNs) in various cell lines. ISG20 plays a role in mediating interferon's antiviral activities. In addition, ISG20 may be a potential susceptibility biomarker or pharmacological target in some inflammatory conditions. Exonucleases are useful components of many physiological processes. Despite recent advances in our understanding of the functions of ISG20, much work remains to be done with regard to uncovering the mechanism of action of ISG20 in specific diseases and adapting ISG20 for use as a biomarker of disease. This review describes current information on ISG20 and its potential use in marking disease. This review describes several research achievements thus far and it seeks to provide some new ideas for future related research.

Therapeutic Potential of Interferon-γ and Its Antagonists in Autoinflammation: Lessons from Murine Models of Systemic Juvenile Idiopathic Arthritis and Macrophage Activation Syndrome

Interferon-γ (IFN-γ) affects immune responses in a complex fashion. Its immunostimulatory actions, such as macrophage activation and induction of T helper 1-type responsiveness, are widely acknowledged, however, as documented by a large body of literature, IFN-γ has also the potential to temper inflammatory processes via other pathways. In autoimmune and autoinflammatory disorders, IFN-γ can either play a disease-enforcing role or act as protective agent, depending on the nature of the disease. In animal models of any particular autoimmune disease, certain changes in the induction procedure can reverse the net outcome of introduction or ablation of IFN-γ. Here, we review the role of endogenous IFN-γ in inflammatory disorders and related murine models, with a focus on systemic juvenile idiopathic arthritis (sJIA) and macrophage activation syndrome (MAS). In particular, we discuss our recent findings in a mouse model of sJIA, in which endogenous IFN-γ acts as a regulatory agent, and compare with results from mouse models of MAS. Also, we elaborate on the complexity in the activity of IFN-γ and the resulting difficulty of predicting its value or that of its antagonists as treatment option.

Interferon gamma suppresses collagen-induced arthritis by regulation of Th17 through the induction of indoleamine-2,3-deoxygenase

C57BL/6 mice are known to be resistant to the development of collagen-induced arthritis (CIA). However, they show a severe arthritic phenotype when the Ifng gene is deleted. Although it has been proposed that IFN-γ suppresses inflammation in CIA via suppressing Th17 which is involved in the pathogenesis of CIA, the exact molecular mechanism of the Th17 regulation by IFN-γ is poorly understood. This study was conducted to 1) clarify that arthritogenic condition of IFN-γ knockout (KO) mice is dependent on the disinhibition of Th17 and 2) demonstrate that IFN-γ-induced indoleamine2,3dioxgenase (IDO) is engaged in the regulation of Th17. The results showed that the IFN-γ KO mice displayed increased levels of IL-17 producing T cells and the exacerbation of arthritis. Also, production of IL-17 by the splenocytes of the IFN-γ KO mice was increased when cultured with type II collagen. When Il17 was deleted from the IFN-γ KO mice, only mild arthritis developed without any progression of the arthritis score. The proportion of CD44^highCD62L^low memory-like T cells were elevated in the spleen, draining lymph node and mesenteric lymph node of IFN-γ KO CIA mice. Meanwhile, CD44^lowCD62L^high naïve T cells were increased in IFN-γ and IL-17 double KO CIA mice. When Th17 polarized CD4+ T cells of IFN-γ KO mice were co-cultured with their own antigen presenting cells (APCs), a greater increase in IL-17 production was observed than in co-culture of the cells from wild type mice. In contrast, when APCs from IFN-γ KO mice were pretreated with IFN-γ, there was a significant reduction in IL-17 in the co-culture system. Of note, pretreatment of 1-methyl-DL- tryptophan, a specific inhibitor of IDO, abolished the inhibitory effects of IFN-γ. Given that IFN-γ is a potent inducer of IDO in APCs, these results suggest that IDO is involved in the regulation of IL-17 by IFN-γ.

Pleiotropic targets: the problem of shared signaling circuitry in rheumatoid arthritis disease progression and protection

The immune response is replete with feedback control at many levels. These protective circuits are even functional within the arthritic joint, tempering disease to varying extents. An optimal therapy would inhibit autoimmune processes while maintaining protective circuitry. However, many of the cells and proteins that serve as important mediators of disease progression also play an active role in these protective circuits. The hypothesis considered in this review is that the inadvertent inhibition of protective circuitry adversely affects efficacy. Conversely, if therapeutics can be designed, which avoid inhibiting known regulatory circuits, efficacy will be improved. Understanding where these processes share signaling molecules will be crucial to the development of the next generation of therapeutics. This review discusses three well-defined signal transduction cascades; IL-2, IFNγ and TNF-α, and demonstrate within two cell types, T cells and macrophages, how these cytokines may contribute both to protection and to disease progression.

Collagen-induced arthritis as an animal model for rheumatoid arthritis: focus on interferon-γ

Rheumatoid arthritis (RA), an autoimmune disease causing inflammation, destruction, and deformity of the joints, affects around 1% of the world population. It is a systemic disease as patients exhibit extra-articular manifestations as well. Collagen-induced arthritis (CIA) in DBA/1 mice is one of the many animal models used to study possible pathogenic mechanisms of RA. It involves immunizing mice with collagen type II in complete Freund's adjuvant. Here we briefly review the general characteristics of RA and CIA and present an overview of data obtained by studying CIA in several gene knockout mice. In particular, detailed analysis of CIA in interferon-gamma (IFN-γ) receptor-deficient mice has pin-pointed IFN-γ as an important cytokine in the pathogenesis and has exposed new functions of IFN-γ in immunological processes. Pilot trials with exogenous IFN-γ in RA have been indicative of a beneficial effect. That improvement of the disease symptoms by IFN-γ treatment was not spectacular may be explained by the fact that RA is a heterogeneous disease in which the severity of the autoimmune disease is strongly determined by environmental factors.

A role of monocyte chemoattractant protein-4 (MCP-4)/CCL13 from chondrocytes in rheumatoid arthritis

We studied the role of monocyte chemoattractant (MCP)-4/CCL13 in the pathogenesis of rheumatoid arthritis (RA). MCP-4 was highly expressed in cartilage from RA patients. Interferon-gamma significantly stimulated MCP-4/CCL13 production in human chondrocytes, and this effect was enhanced in combination with interleukin-1beta or tumor necrosis factor-alpha. MCP-4/CCL13 induces the phosphorylation of extracellular signal-regulated kinase in fibroblast-like synoviocytes and activates cell proliferation, and PD98059 completely inhibits these effects. These data suggest that interferon-gamma in combination with interleukin-1beta/tumor necrosis factor-alpha activates the production of MCP-4/CCL13 from chondrocytes in RA joints, and that secreted MCP-4/CCL13 enhances fibroblast-like synoviocyte proliferation by activating the extracellular signal-regulated kinase mitogen-activated protein kinase cascade.

Exacerbation of antigen-induced arthritis in IFN-gamma-deficient mice as a result of unrestricted IL-17 response

Proinflammatory Th1 responses are believed to be involved in the induction and perpetuation of rheumatoid arthritis. However, the role of IFN-gamma, the major cytokine produced by Th1 cells, is still incompletely defined. In the present study, we investigated the effects of IFN-gamma deficiency (IFN-gamma(-/-)) on the course of experimental murine Ag-induced arthritis (AIA). In the acute stage of disease, IFN-gamma(-/-) AIA mice showed significantly increased inflammatory responses compared with wild-type C57BL/6 AIA mice, i.e., exacerbated joint swelling, increased delayed-type hypersensitivity reaction, and increased histopathological scores of arthritis. Intraarticular administration of exogenous IFN-gamma at induction of AIA significantly suppressed these acute aggravation effects. Stimulated cells isolated from lymph nodes and spleen of IFN-gamma(-/-) AIA mice showed increased production of IL-2, IL-4, IL-5, IL-6, but most prominently of IL-17. These elevations were paralleled by decreased humoral immune responses, with low serum levels of total and Ag-specific IgG (IgG1, IgG2a(b), IgG2b, IgG3). At immunohistology, the knee joints of IFN-gamma(-/-) AIA mice showed massive neutrophil granulocyte infiltration. Treatment with mAbs neutralizing IL-17 diminished the acute inflammation. In vitro, Th cell expansion and production of IL-17 upon restimulation were effectively and dose dependently inhibited by IFN-gamma. These results clearly demonstrate that IFN-gamma has anti-inflammatory properties during the initial phase of AIA, and indicate that IFN-gamma deficiency exerts disease-promoting effects, preferentially via IL-17-modulated pathways.

Inflammatory arthritis can be reined in by CpG-induced DC-NK cell cross talk

Unmethylated CpG-oligodeoxynucleotides (ODNs) are generally thought of as potent adjuvants with considerable therapeutic potential to enhance immune responses against microbes and tumors. Surprisingly, certain so-called stimulatory CpG-ODNs strongly inhibited the effector phase of inflammatory arthritis in the K/BxN serum transfer system, either preventively or therapeutically. Also unexpected was that the inhibitory influence did not depend on the adaptive immune system cells mobilized in an immunostimulatory context. Instead, they relied on cells of the innate immune system, specifically on cross talk between CD8α⁺ dendritic cells and natural killer cells, resulting in suppression of neutrophil recruitment to the joint, orchestrated through interleukin-12 and interferon-γ. These findings highlight potential applications of CpG-ODNs and downstream molecules as antiinflammatory agents.

Protective role of IFN-gamma in collagen-induced arthritis conferred by inhibition of mycobacteria-induced granulocyte chemotactic protein-2 production

Mice with a disrupted IFN-gamma system are remarkably susceptible to experimental autoimmune diseases, such as collagen-induced arthritis (CIA), which rely on the use of CFA. The inflammatory lesions of these IFN-gamma knockout (KO) mice are characterized by an excessive proportion of neutrophils. Here, we show that the increased severity of CIA in IFN-gammaR KO as compared with wild-type mice is accompanied by increased levels of the CXC chemokine granulocyte chemotactic protein-2 (GCP-2), a major neutrophil-attracting chemokine in mice. We demonstrated that the heat-killed mycobacteria present in CFA elicited production of GCP-2 in mouse embryo fibroblast cultures and that this production was inhibited by IFN-gamma. Inhibition of GCP-2 production by IFN-gamma was STAT-1-dependent. IFN-gamma receptor KO mice treated with neutralizing anti-GCP-2 antibodies were protected from CIA, indicating the in vivo importance of GCP-2 in the pathogenesis of CIA. Our data support the notion that one of the mechanisms whereby endogenous IFN-gamma mitigates the manifestations of CIA consists of inhibiting production of GCP-2, thereby limiting mobilization and infiltration of neutrophils, which are important actors in joint inflammation. These results may also be applicable to other experimental models of autoimmunity that rely on the use of CFA.

Interferons and their application in the diseases of the lung

Interferons (IFNs) are a family of cytokine mediators that are critically involved in alerting the cellular immune system to viral infections of host cells. There are three major classes of IFNs, as follows: IFN-alpha; IFN-beta; and IFN-gamma. IFNs are being investigated and applied in various respiratory disorders, including interstitial lung diseases, lung cancer, malignant mesothelioma, malignant pleural effusions, and respiratory infections. Recent promising preliminary results concerning patients with idiopathic pulmonary fibrosis who have been treated with IFN-gamma1b should prompt the performance of further confirmatory well-designed multicenter trials. IFN-gamma is emerging as an important cytokine for use in the treatment of patients with infectious diseases, including multidrug-resistant pulmonary TB. A better understanding of IFN biology, indications, side effect profiles, and toxicity management will aid in optimizing its use in the treatment of patients. The purpose of this article is, therefore, to review the current clinical use of IFNs in the treatment of patients with respiratory diseases.

Juvenile rheumatoid arthritis: therapeutic perspectives

Juvenile rheumatoid arthritis (JRA) is the most common childhood chronic systemic autoimmune inflammatory disease. The therapeutic approach to JRA has, to date, been casual and based on extensions of clinical experiences gained in the management of adult rheumatoid arthritis (RA). The physiology of inflammation has been systemically studied and this has led to the identification of specific therapeutic targets and the development of novel approaches to the management of JRA. The classical treatments of the disease such as methotrexate, sodium aurothiomalate and sulfasalazine, are not always effective in controlling RA and JRA. This has necessitated the development of novel agents for treating RA, most of which are biological in nature and are targeted at specific sites of the inflammatory cascades. These biological therapeutic strategies in RA have proved successful and are being applied in the management of JRA. These developments have been facilitated by the advances in molecular biology which have heralded the advent of biodrugs (recombinant proteins) and gene therapy, in which specific genes can be introduced locally to enhance in vivo gene expression or suppress gene(s) of interest with a view to down-regulating inflammation. Some of these biodrugs, such as anti-tumor necrosis factor alpha (anti-TNFalpha), monoclonal antibodies (infliximab, adalimumab), TNF soluble receptor constructs (etanercept) and interleukin-1 receptor antagonist (IL-1Ra) have been tested and shown to be effective in RA. Etanercept has now been licensed for JRA. Clinical trials of infliximab in JRA are planned. Studies show that the clinical effects are transient, necessitating repeated treatments and the risk of vaccination effects. Anti-inflammatory cytokines such as IL-4, IL-10, transforming growth factor-beta and interferon-beta (IFN-beta) are undergoing clinical trials. Many of these agents have to be administered parenterally and production costs are very high; thus, there is a need, especially for pediatric use, to develop agents that can be taken orally. Long-term studies will be required to assess the tolerability and toxicity of these approaches in JRA, since cytokines and other mediators play important roles in host defenses, and the chronic inhibition, exogenous administration or constitutive over-expression of some cytokines/mediators may have undesirable effects.

Genetic ablation of interferon-gamma up-regulates interleukin-1beta expression and enables the elicitation of collagen-induced arthritis in a nonsusceptible mouse strain

OBJECTIVE

To determine whether the lack of interferon-gamma (IFNgamma) alters resistance to collagen-induced arthritis (CIA) in a nonsusceptible mouse strain, and if so, to identify changes in the antibody, cellular type II collagen (CII)-specific immune responses, and cytokine gene expression that might account for the altered susceptibility.

METHODS

CIA-resistant C57BL/6 and C57BL/6 IFNgamma-/- mice were immunized with bovine CII in Freund's complete adjuvant (CFA) or in CFA alone. Animals were monitored for signs of arthritis for up to 80 days; arthritis severity was assessed visually and histologically. Sera were collected at various time points after immunization for measurement of anti-CII antibody levels. T cell responses to bovine CII were assessed in proliferation assays. Cytokine messenger RNA (mRNA) expression in lymph node cells and in synovial cells from arthritic paws was measured by RNase protection assays, and levels of cytokine protein production were determined by enzyme-linked immunosorbent assay.

RESULTS

IFNgamma-/- mice developed a severe autoimmune arthritis that was dependent on immunization with CII. IFNgamma-/- mice produced significantly higher amounts of IgG1 and IgG2b antibody to the autoantigen, murine CII, compared with wild-type C57BL/6 mice and had an enhanced T cell proliferative response to bovine CII. Enhanced production of mature interleukin-1/beta (IL-1beta) protein was observed, but no significant changes in Th1 or Th2 cytokines. Although IL-6 and tumor necrosis factor alpha transcripts were clearly evident in the synovial cells from the arthritic paws of IFNgamma-/- mice, neither message was elevated to the levels measured for IL-1beta expression. Treatment of IFNgamma-/- mice with anti-IL-1beta significantly reduced the incidence and severity of the inflammation.

CONCLUSION

Endogenous IFNgamma plays a role in the regulation of IL-1beta, in this model of autoimmune arthritis.

Modulation of human chondrocyte metabolism by recombinant human interferon

OBJECTIVES

Interferon gamma (IFN gamma) is found to be elevated in the synovial fluid of patients with rheumatoid arthritis and osteoarthritis, suggesting its implication in joint disease pathogenesis. In this study, we investigated the effects of IFN gamma on the production of cytokines (IL-6, IL-8, IL-10), prostaglandin E(2)(PGE(2)), proteoglycans (PG), nitric oxide (NO), interleukin-1 receptor antagonist (IL-1ra) and stromelysin by non-stimulated and IL-1 beta-treated human chondrocytes. The role played by NO in the responses of chondrocytes to IFN gamma was also examined by incubation of chondrocytes with N(G)-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of NO synthase.

METHODS

Enzymatically isolated human chondrocytes were cultured for 48 h in the absence or presence of IL-1 beta, IFN gamma or N(G)-monomethyl-L-arginine (L-NMMA) added solely or in combination. The productions of IL-6, IL-8, IL-10, IL-1ra and stromelysin were measured by enzyme amplified sensitivity immunoassays (EASIA). PG and PGE(2)were quantified by specific radioimmunoassays (RIA). Nitrite concentrations in the culture supernatants were determined by a spectrophotometric method based upon the Griess reaction.

RESULTS

As expected, IL-1 beta highly stimulated NO, IL-6, IL-8, IL-10, IL-1ra, PGE(2)and stromelysin synthesis, but dramatically decreased PG production. NO, IL-6, IL-1ra and PGE(2)production by non-stimulated chondrocytes was dose-dependently increased by IFN gamma while PG production was inhibited. In the absence of IL-1 beta, IL-10 was undetectable in the culture supernatants. At the doses of 10 and 100 U/ml, IFN gamma markedly inhibited the constitutive and IL-1 beta-stimulated IL-8, IL-10 and stromelysin productions. Interestingly, IFN gamma synergized with IL-1 beta to increase NO, IL-6, IL-1ra and to depress PG production. As previously reported, the inhibition of NO synthesis by the competitive inhibitor L-NMMA led to enhancement of IL-6, IL-8 and PGE(2)production by IL-1 beta treated chondrocytes, but did not significantly modify IL-10, PG and MMP-3 productions. Inhibition of NO synthase significantly inhibited the stimulating effect of IFN gamma on IL-6 and IL-1ra but did not affect the inhibitory effect of IFN gamma on IL-8, PG or stromelysin production.

CONCLUSIONS

These findings suggest that IFN gamma and IL-1 synergistically stimulate the production of IL-6, IL-1ra, NO and PGE(2)and inhibit PG synthesis. By contrast, IL-1 beta and IFN gamma have opposite effects on IL-8, IL-10 and stromelysin productions. These effects are not reversed by L-NMMA, suggesting that NO is not the principal mediator involved in responses of chondrocytes to IFN gamma.

Gamma interferon prevents diabetes in the BB rat

The BB rat model of human insulin-dependent diabetes mellitus (IDDM) spontaneously develops diabetes through an autoimmune process. Gamma interferon (IFN-gamma) is thought to play an important pathogenic role. This study examined if IFN-gamma administration can, paradoxically, prevent diabetes in BB rats. Diabetes-prone BB rats were initially injected intraperitoneally with murine recombinant IFN-gamma (rIFN-gamma) at doses of 0.5 x 10(4) to 40 x 10(4) U three times a week for 6 weeks beginning at 35 days of age. The effects of altering the duration of treatment (2 to 6 weeks) and the age at which injections were initiated (45 through 65 days) were also assessed. rIFN-gamma administration prevented the development of diabetes in a dose-dependent manner. The optimal treatment condition resulted in a 9.1% incidence of diabetes versus a 90% incidence in control rats. This diabetes-sparing effect was long lasting and continued to 7 months of age. A 4- to 6-week course resulted in maximal inhibition. Treatment initiated as late as 55 days of age, when insulitis is already present, was effective in preventing diabetes. Islet inflammation was dramatically lower in rIFN-gamma- versus saline-injected rats (P < 0.01). Total leukocyte count and subpopulations of peripheral mononuclear cells were unaltered by rIFN-gamma. In summary, rIFN-gamma paradoxically and potently prevents diabetes in BB rats in a dose-dependent fashion by inhibiting islet inflammation. This diabetes-sparing effect occurs even when injections are initiated after evidence of the diabetic process is already present.

A primer on cytokines: sources, receptors, effects, and inducers

Protection against pathogens is a prerequisite for survival of most organisms. To cope with this continuous challenge, complex defense mechanisms have evolved. The construction, adaptation, and maintenance of these mechanisms are under control of an extensive network of regulatory proteins called cytokines. A great number of cytokines have been described over the last 2 decades. This review consists of an overview of cytokines that are involved in immune responses and describes some historical and general aspects as well as prospective clinical applications. Major biological effects together with information on cytokine receptors, producers, inducers, and biochemical and molecular characteristics are listed in tables. In addition, some basic information is given on cytokine receptor signal transduction. Finally, the recent discoveries of cytokine receptors functioning as coreceptors in the pathogenesis of human immunodeficiency virus are summarized.

Treatment of chronic recurrent multifocal osteomyelitis with interferon gamma

Chronic recurrent multifocal osteomyelitis is characterized by recurrent episodes of painful swollen lesions of the bone and overlying skin with radiographic changes and an elevated sedimentation rate. It resembles infectious osteomyelitis but with negative findings on bacterial culture and no response to antibiotics. We treated a 13-year-old girl with interferon gamma for 3 months. She had 11 episodes of chronic recurrent multifocal osteomyelitis in 2 1/2 years before therapy and has had none in the 15 months since therapy, an outcome suggesting a favorable therapeutic response.

A randomized, double-blind study comparing twenty-four-week treatment with recombinant interferon-gamma versus placebo in the treatment of rheumatoid arthritis

OBJECTIVE

To evaluate the safety and efficacy of recombinant interferon-gamma (rIFN gamma) in patients with active rheumatoid arthritis (RA), using an induction and maintenance regimen.

METHODS

A multicenter, randomized, double-blind trial of 197 patients with RA was conducted to compare the effects in a group receiving 50 micrograms of rIFN gamma, given subcutaneously in a decreasing regimen over 24 weeks, with those in a placebo group receiving injections of placebo at the same time frequency. Standard clinical assessments were performed.

RESULTS

Both rIFN gamma and placebo produced a significant improvement from baseline to end point visit for most measurements (except erythrocyte sedimentation rate, duration of morning stiffness, and grip strength), but no significant intergroup differences were seen. Regarding adverse effects, mild local skin reactions at the site of injection were observed, and among the cardiovascular events, mild edema and vasodilatation were reported.

CONCLUSION

IFN gamma proved no more effective than placebo in this group of patients with RA. IFN gamma was well tolerated in this group of patients, without increased toxicity compared with placebo.

Reproductive effects of chronic administration of murine interferon-gamma

Daily subcutaneous doses of 0.02, 0.2, or 2 mg/kg/d of recombinant murine interferon-gamma (rmuIFN-gamma) were given to mice on postnatal days 8 through 60 to determine effects on maturation, behavioral/ functional development, and reproductive capacity. Male mice receiving 2 mg/kg/d rmuIFN-gamma had delayed sexual maturation, reduced epididymal and testes weights, reduced sperm count and concentration, and sperm abnormalities (crimped flagellum). Mating performance and fertility were also reduced in the absence of altered histopathology of the testes. Males given 0.2 and 2 mg/kg/d had swelling and ulcerative dermatitis around the urogenital area, which were observed after sexual contact and attributed to a bacterial infection. Motor activity (time spent in movement) was decreased in all mice receiving 2 mg/kg/d. No microscopic changes observed in any organs were attributed to rmuIFN-gamma administration.

Specific drugs for a complex disease: can there be a magic bullet against rheumatoid arthritis?

The complexity of RA challenges our search for a better understanding of the interconnected networks. Early treatment will certainly avoid some of the problems presented by the complexity of the disease, and combined treatments seem advantageous for advanced disease. The complexity of overt RA will probably not allow a single agent to exert superior efficacy. Unless a treatable infectious cause is identified, a magic bullet, though theoretically possible, might not exist in reality, in particular if the disease is advanced.

Induction of autoimmune phenomena in patients with chronic hepatitis B treated with gamma-interferon

All interferons display antiviral properties, but gamma-interferon especially has an immunomodulatory effect and may induce autoimmune phenomena. Therefore the formation of autoantibodies was investigated in patients with chronic hepatitis B treated with gamma-interferon. Eleven patients (all HBs-Ag and HBe-Ag positive) were treated for 6 months with recombinant gamma-interferon. The following antibodies were tested: anti-nuclear antibodies, smooth muscle antibodies, anti-actin, anti-mitochondrial antibodies of subgroup anti-M2 and anti-M9 as well as naturally occurring antibodies, antibodies to liver-kidney microsomes, vascular endothelial cell antibodies, sarcolemmal antibodies, parietal cell antibodies, thyroglobulin antibodies and antibodies to laminin and keratin. All patients produced autoantibodies during therapy. The maximum antibody formation and the highest titres were observed in the period between the 3rd and 6th month after therapy began. The cumulative frequencies of the different antibody specificities were as follows: n = 6 anti-nuclear antibodies, n = 7 smooth muscle antibodies, n = 1 anti-actin, n = 12 antibodies to laminin or keratin, n = 6 endothelial cell antibodies/sarcolemmal antibodies, n = 6 anti-mitochondrial antibodies, n = 1 antibodies to liver-kidney microsomes, n = 2 thyroglobulin antibodies, n = 4 parietal cell antibodies. Antibodies persisted in six patients over a period of 3 months (two cases of parietal cell antibodies and one case of antibodies to liver-kidney microsomes) and were still detectable in three patients 6 months after therapy. In three patients new antibody formation occurred 1 month after therapy. So far, clinical signs of an autoimmune disorder have not appeared in any of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

New approaches to the therapy of autoimmune diseases: rheumatoid arthritis as a paradigm

Several therapeutic agents currently are used to treat rheumatoid arthritis (RA). However, there is no compelling evidence that any of these agents substantially alters the long-term destructive course of RA. Advances in biotechnology have led to a better understanding of mechanisms that underlie autoimmune diseases such as RA. Although the etiology of RA remains unknown, there now is considerable insight regarding the immune and inflammatory pathways that ultimately lead to cartilage and bone destruction. Therapies with monoclonal antibodies directed against cell surface constituents, fusion toxins against cell activation markers, and cytokine inhibitors all have been shown to be safe and possibly efficacious in early open trials in RA. They now are being more rigorously tested in double-blind, placebo-controlled trials. Early experience with these biologic agents in humans, as well as data obtained from the use of these agents in animal models of autoimmune disease, are reviewed. In addition, experimental studies with "blocking peptides" and immunization with autoreactive T cell receptor peptides will be reviewed, and implications for therapy in RA will be discussed.

Double blind controlled phase III multicenter clinical trial with interferon gamma in rheumatoid arthritis. German Lymphokine Study Group

The controlled clinical trial reported here is part of a multicenter clinical and basic research project, sponsored by the German Federal Minister of Science and Technology, directed by a standing commission of the president of the Max-Planck-Gesellschaft, and coordinated by the Max-Planck-Institut für Biochemie, München. Overall, 249 patients with rheumatoid arthritis (RA) were enrolled by 16 participating hospitals. In addition to NSAID treatment, patients were randomly given either interferon gamma (IFN-gamma) or placebo. In the IFN-gamma group, 107 patients were evaluated and in the control group, 116 patients were evaluated. The response rate after 3 months of treatment, according to joint pain indexes, was significantly higher in the IFN-gamma group with an error probability of 1%. IFN-gamma was able to reduce the quantity of corticosteroids administered. Compared with the control group, the IFN-gamma group benefited considering all parameters measured. Most important side effects were transient fever and transient influenza-like symptoms; all other adverse events were comparable in both groups.

Recombinant human interferon gamma in the treatment of rheumatoid arthritis: double blind placebo controlled study

Interferon gamma (IFN gamma) has been advocated in open studies as a beneficial remission inducing drug for the treatment of rheumatoid arthritis (RA). The work reported here was designed to assess the therapeutic potential of IFN gamma in the treatment of RA in a double blind placebo controlled study. It was found that patients treated with IFN gamma improved significantly with respect to morning stiffness, grip strength, swelling of an index joint, and erythrocyte sedimentation rate. Furthermore significantly more responders (according to predetermined response criteria) were found in the group treated with IFN gamma. Only minor adverse effects and no significant toxicity with respect to clinical or laboratory parameters were observed.

Murine hypersensitivity pneumonitis: bidirectional role of interferon-gamma

C57BL/6 mice were instilled intranasally with optimal doses [150 micrograms of antigen 3 days a week) of the actinomycete Faeni rectivirgula to induce an experimental hypersensitivity pneumonitis. Some control mice received normal rat IgG as controls, whereas other mice received 1 mg weekly of rat anti-murine interferon gamma (IFN-gamma) antibody by the intraperitoneal route and 200 micrograms by the intranasal route given 2 days before and during the challenge period before each instillation. Control mice developed a clear hypersensitivity pneumonitis characterized by an early neutrophilic response at 3 days and a later influx of mononuclear cells (nine- to tenfold increase in cell number. P less than 0.001 vs saline instilled mice at 4 weeks post-treatment). F. rectivirgula instillation determined a sharp increase in the lung index (80% increase in lung weight, P less than 0.005 vs saline treated mice), as well as a significant fibrosis at 4 weeks (twofold increase in lung hydroxyproline levels). Cytokine measurements showed that tumour necrosis factor alpha (TNF alpha) was present in the broncho-alveolar lavage (BAL) of challenged mice at 4 weeks when the BAL was obtained 8 hr after the last challenge (130 U/ml). Treatment of mice with the monoclonal antibody against IFN-gamma was associated with very few changes in the number of cells in the BAL of challenged mice. The lung index of challenged mice was significantly reduced by infusion of the anti-IFN-gamma antibody. Anti-IFN-gamma treatment resulted in decreased levels of TNF alpha in the BAL of F. rectivirgula after 4 weeks of treatment (56 U/ml, P less than 0.01). Moreover, depletion of endogenous IFN-gamma in F. rectivirgula-instilled mice resulted in a diminished lung fibrotic response (P less than 0.01 vs mice treated with F. rectivirgula and control antibody). We also studied the effect of exogenous IFN-gamma adminstration on the development of lung disease. Groups of mice received recombinant gamma interferon (IFN-gamma) (1000 U) intraperitoneally just before the first treatment and also daily, whereas controls received saline or IFN-gamma alone (no F. rectivirgula challenge). After 4 weeks of treatment, mice were killed and various markers of the disease were evaluated. As mentioned before, bronchoalveolar lavage (BAL) cell number was increased tenfold in mice treated with F. rectivirgula, whereas mice given F. rectivirgula and IFN-gamma had only a threefold increase in BAL cell number, determined mostly by a decrease in alveolar macrophage recruitment in the lungs.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of interferon gamma production by peripheral blood mononuclear leukocytes of patients with sarcoidosis. Pathogenic implications

Interferon gamma (IFN-gamma) production by stimulated peripheral mononuclear leukocytes of 30 patients with sarcoidosis was studied. A significant inhibition (64 percent, 5 to 330 IU/ml vs normal individuals = 1,000 +/- 250 IU/ml) in the IFN-gamma synthesis was found. The inhibition is due to a defect in the circulating monocytes and not in the peripheral T lymphocytes of these patients. This defect in the peripheral IFN-gamma production could be involved in the pathogenesis of this disease.

A prospective randomized comparison of single-agent interferon (IFN)-alpha with the combination of IFN-alpha and low-dose IFN-gamma in chronic myelogenous leukaemia

In patients with previously untreated chronic myelogenous leukaemia (CML) the efficacy of single-agent interferon (IFN)-alpha at an initial dose of 4 x 10(6) U/m2 (arm A) was compared with the combined administration of the identical dose IFN-alpha plus a total dose of 50 micrograms IFN-gamma (arm B). 51 patients entered this study between April 1987 and October 1989; the analysis was performed in March 1991 and was focused on response rates and toxicity. 54% of patients on arm A and 56% of arm B patients attained haematologic remission. 29% of patients on arm A and 24% of arm B patients had partial haematologic remission. A decrease in Philadelphia chromosome (Ph)-positive metaphases of more than 10% was only seen in patients who had achieved complete haematologic normalization. In 21% of patients on arm A and 20% of arm B patients, the percentage of Ph-positive cells declined to less than 35%. Toxicity was different between the two study groups with more pronounced hepatotoxicity observed in patients treated with IFN-alpha alone. Among the patients receiving both IFNs, alpha and gamma, there were 2 fatal infectious complications. This serious toxicity in conjunction with lack of a clinically meaningful difference between the two treatment schedules has led us to terminate the study. In conclusion, the addition of low-dose IFN-gamma failed to improve the efficacy of IFN-alpha in this study.

Antifibrotic and uveitogenic properties of gamma interferon in the rabbit eye

The feasibility of gamma (gamma)-interferon injection for the treatment of ocular fibrotic conditions was studied in rabbits using recombinant rabbit gamma-interferon and the cell-injection model of tractional detachment. A toxicity study revealed that intravitreal injection of greater than 10(4) units gamma-interferon consistently produced panuveitis. For tractional detachment, 250,000 rabbit dermal fibroblasts were injected intravitreally into 20 eyes; 1 day later, 5 of these eyes received intravitreal injections of 10(4) units gamma-interferon, another 5 were given 10(6) units, and the remaining 10 received balanced salt solution. Slit-lamp examination and fundus photography were performed at regular intervals for 21 days and were graded by a masked observer. The eyes were then enucleated and processed for histology. Doses of 10(4) units gamma-interferon significantly reduced the severity of detachments, but injections of 10(6) units induced panuveitis.

The effect of treatment with recombinant gamma-interferon on adjuvant-induced arthritis in rats

We have investigated the effects of recombinant rat gamma-interferon (rIFN gamma) on adjuvant-induced arthritis (AA). Lewis rats, inoculated in the left hind-paw with adjuvant (day 0), were given 10(5) U/rat of rIFN gamma daily (days 0 to 20), subcutaneously and intramuscularly on alternate days. rIFN gamma suppressed the secondary phase of swelling of both hind-paw on and after day 18 without influencing the earlier phases, both primary and secondary, of swelling. rIFN gamma also reduced the hind-paw bone lesions, the degree of splenomegaly, and the increase in erythrocyte sedimentation rate and plasma fibrinogen. These results indicate a new aspect of the regulatory role of IFN gamma in chronic inflammation.

Interleukin-1-like activity in normal rat skin after in vivo treatment with interferon-gamma

The influence of interferon-gamma (IFN-gamma) on immune responses is still ambiguous. We have investigated whether IFN-gamma influences the constitutive interleukin-1 (IL-1)-like activity in normal rat skin because IL-1 is a regulatory cytokine in immune responses. Rats were injected intradermally into both ears with different doses of rat recombinant IFN-gamma (10(3)-10(5) U), and control animals were given phosphate-buffered saline (PBS). The animals were killed at different times and the ears were cut off at the bases. The biologic activity of the IFN-gamma was verified by immunohistochemistry on injected ears, showing a time- and dose-dependent induction of major histocompatibility complex class II antigens on the keratinocytes. Aqueous extracts of homogenized ear skin were tested for IL-1-like activity in a mouse thymocyte bioassay. No major effects of IFN-gamma on the constitutive IL-1-like activity in the rat skin were found; at 6 h there was a slight reduction and at 72 h an increase in IL-1 bioactivity in extracts from IFN-gamma (10(5) U)-injected animals compared with PBS-treated controls (p less than 0.05). We conclude that the regulation of immune responses in the rat skin by IFN-gamma is less likely to be mediated via changes in the IL-1-like activity.

Successful treatment of primary progressive follicular mucinosis with interferons

Follicular mucinosis is a primary idiopathic disease or a secondary, lymphoma-associated dermatosis. An effective standard therapy for the benign group is unknown. We describe a patient with primary benign disseminated progressive follicular mucinosis who was successfully treated with recombinant interferon alfa-2b and interferon-gamma. Interferons might act by down-regulation of activated inflammatory cells and/or by induction of enhanced elimination of extracellular mucin via increasing phagocytosis by macrophages.

Suppression of bacterial cell wall-induced polyarthritis by recombinant gamma interferon

Group A streptococcal cell wall fragments (SCW) induce erosive polyarthritis, characterized by synovial cell hyperplasia and intense mononuclear cell infiltration, in susceptible rats. Because of the known antiproliferative and immunomodulatory effects of interferon (IFN), we evaluated the effect of systemically administered alpha, beta and gamma IFN on the evolution of these destructive lesions. Treatment with gamma IFN not only reduced the acute response, but had an even greater suppressive effect on the chronic mononuclear cell-mediated destructive phase of the disease (articular index 10.2 +/- 1.2 for SCW only versus 3.8 +/- 0.7 for SCW + gamma IFN; p less than 0.01). Treatment with gamma IFN was more effective in the suppression of the arthritis than alpha, beta IFN. Histopathologic evaluation of the joints demonstrated that gamma IFN-treated animals had significantly fewer inflammatory cells, and less synovial hyperplasia and erosions than the SCW controls. gamma IFN suppression of mononuclear cell prostaglandin synthesis and synovial fibroblast proliferation was consistent with its anti-arthritic effects. These data indicate that the pathophysiology of SCW-induced erosive polyarthritis is subject to regulatory control by gamma IFN and that the mechanisms of suppression may be relevant in the treatment of rheumatoid arthritis.

New approaches for antirheumatic therapy

New approaches for antirheumatic therapy are firmly based on current knowledge of immunopathogenic processes. Specific immunotherapy is directed at the treatment of the disease per se and not the production of generalized immunosuppression with its unwanted side-effects. The three targets against which specific immunotherapy is directed are the T cell receptor, the HLA antigen linked to the disease and the antigenic peptide involved in the initiation and/or persistence of the disease. Therapies directed against lymphokines, monokines and cytokines produced during the chronic immune-mediated inflammation are also being developed but they may be unsuccessful not only because of the great redundancy inbuilt into the inflammatory response but also because they would produce too general a response with possibilities of harmful side-effects. Specific immunotherapy at present is largely through the use of monoclonal antibodies directed against a variety of T cell membrane antigens such as CD4, CD7 and the interleukin 2 receptor. A possible therapy is monoclonal antibodies, directed against the HLA molecule involved in the aetiopathogenesis of disease. The use of disease-causing T cell lines or clones as vaccines or therapeutic agents has solid experimental support and studies are in progress in patients with rheumatoid arthritis using T cell lines grown from synovial fluid aspirates. If successful, such therapy could be modified to the use of short peptide fragments from the relevant T cell receptor. T cells recognize antigenic peptides presented on the surface of antigen-presenting cells within a groove formed by the HLA molecule. Displacement of disease-inducing antigenic peptides by engineered 'neutral' peptides could offer a very precise form of immunotherapy. Many of these approaches are based on the hypothesis that transient but effective switching-off of the disease process may allow immunoregulatory circuits, as yet poorly defined, to come into play to permanently cure the disease. Many such therapies are in the offing. It may be that they have to be used in various combinations in order to achieve cure. For this complex and time-consuming task to attain that desired consummation, co-operative interaction between many clinicians, basic scientists and patients will be required. It is to that cooperation that we dedicate this chapter on new approaches for antirheumatic therapy.

Interferons and collagen production

The immunoregulatory, antiviral, and antiproliferative agents known as the interferons have profound effects on collagen synthesis. Interferons alpha, beta, and gamma suppress collagen synthesis by dermal fibroblasts. In addition, interferon gamma (IFN-gamma) inhibits the constitutively increased collagen synthesis characteristic of fibroblasts derived from lesions of patients with scleroderma. IFN-gamma also inhibits collagen synthesis by myofibroblasts and synovial fibroblast-like cells. Inhibition of collagen synthesis by IFN-gamma is associated with a coordinate inhibition of transcription for types I and III collagen. In addition, IFN-gamma suppresses levels of procollagen mRNA and type II collagen synthesis in human articular chondrocytes. In vivo studies in mice have demonstrated that IFN-gamma inhibits the collagen synthesis associated with the fibrotic response to an implanted foreign body, bleomycin-induced pulmonary fibrosis, and the healing response to cutaneous thermal burns. In the latter case, while collagen content of the wound scar was decreased, hyaluronic acid was increased in mice receiving IFN-gamma compared to controls. This is in accord with in vitro studies showing that, while interferons alpha and beta decrease production of glycosaminoglycans, IFN-gamma increases production of glycosaminoglycans. Of interest, acute inflammation at sites of thermal injury, or when elicited by proinflammatory agents in separate experiments, also was suppressed in mice treated with IFN-gamma. The means by which IFN-gamma inhibits collagen synthesis involves transcriptional regulation. There is a single report that interferon alpha can decrease the size of a keloid of recent onset in a human patient. Because the interferons can inhibit collagen synthesis in vivo, further studies may be warranted to evaluate the usefulness of these agents in the treatment of disease states characterized by abnormal fibrotic responses as well as their potential for altering the healing response associated with particular therapeutic interventions.

Cytokines in chronic inflammatory arthritis. V. Mutual antagonism between interferon-gamma and tumor necrosis factor-alpha on HLA-DR expression, proliferation, collagenase production, and granulocyte macrophage colony-stimulating factor production by rheumatoid arthritis synoviocytes

The effects of a broad array of cytokines, individually and in combination, were determined on separate functions (proliferation, collagenase production, and granulocyte macrophage colony-stimulating factor [GM-CSF] production) and phenotype (expression of class II MHC antigens) of cultured fibroblast-like RA synoviocytes. The following recombinant cytokines were used: IL-1 beta, IL-2, IL-3, IL-4, IFN-gamma, tumor necrosis factor (TNF)-alpha, GM-CSF, and macrophage colony-stimulating factor (M-CSF). Only IFN-gamma induced HLA-DR (but not HLA-DQ) expression. TNF-alpha inhibited IFN-gamma-mediated HLA-DR expression (46.7 +/- 4.1% inhibition) and HLA-DR mRNA accumulation. This inhibitory effect was also observed in osteoarthritis synoviocytes. Only TNF-alpha and IL-1 increased synoviocyte proliferation (stimulation index 3.60 +/- 1.03 and 2.31 +/- 0.46, respectively). IFN-gamma (but none of the other cytokines) inhibited TNF-alpha-induced proliferation (70 +/- 14% inhibition) without affecting the activity of IL-1. Only IL-1 beta and TNF-alpha induced collagenase production (from less than 0.10 U/ml to 1.10 +/- 0.15 and 0.72 +/- 0.24, respectively). IFN-gamma decreased TNF-alpha-mediated collagenase production (69 +/- 19% inhibition) and GM-CSF production but had no effect on the action of IL-1. These data demonstrate mutual antagonism between IFN-gamma and TNF-alpha on fibroblast-like synoviocytes and suggest a novel homeostatic control mechanism that might be defective in RA where very little IFN-gamma is produced.

Biologic effects of interferons

If one were to review articles on IFN published between 1957 and 1967 it would become apparent that virtually none of the tenets held then are still valid today. Whereas IFN was long considered to be a specific antiviral substance without any effect on normal cellular metabolism, we accept today that it affects normal cell division and many specialized cellular functions. In this respect it is not unique; IFN is a prototype of a family of similar substances now called cytokines that all appear to function as regulatory molecules. It was held that the production of IFN constituted a specific response to a viral infection. Today we believe that IFN is an integral part of a cytokine network and that they and other cytokines may be produced constitutively at low levels. These substances exert multiple effects on virtually all cells. They play an important role in host defense against viral and parasitic infections, and in the resistance to experimental tumors. IFN can be shown to exert effects on the immune system and on lymphocyte circulation. Lastly, because of the multiplicity of their biologic effects, they may even contribute to the pathogenesis of certain diseases. Thus, when large amounts of IFN are administered or induced in newborn mice they can cause liver, kidney, and pulmonary disease. The field of IFN and cytokine research continues to expand and there is an increasing number of therapeutic applications. Twenty years from now, scientists and clinicians may be surprised that we understood so little of how IFN act and how inadequately we used them to treat disease.

Treatment of psoriasis and psoriatic arthritis with interferon gamma

In a placebo-controlled double-blind randomized study, 24 patients with psoriatic arthritis were given 28 d of treatment, and in an open study, 56 patients were treated for 9 months. We treated patients with 100 micrograms IFN gamma per subcutaneous injections, which were given daily for the first 2 weeks and then 3 times per week. The principal criterion for evaluation of therapeutic success on arthritis was improvement of the Ritchie joint pain index by at least 25% in the double-blind and 30% in the long-term study. In the double-blind study, the interferon arm was superior to the placebo arm with a statistically significant, one-side error probability of less than 5% in the chi-square test. In the long-term study, IFN gamma caused an improvement in a portion of patients in the first 3 months of therapy. No further improvement was observed after the third month, and patients classified as responders in the first months showed a deterioration of the disease by continuing treatment. The humoral inflammatory parameters did not normalize during therapy. Regression of the skin manifestations could not be observed. IFN gamma is evidently capable of inducing a psoriasis on the injection site. Investigations of IFN gamma serum levels, IFN antibodies, 2'-5' A synthetase levels in serum, and mononuclear blood cells and NK cell activity under long-term therapy showed no explanation for the loss of efficacy after 3 months treatment.