Changes in cell surface antigen expression on human articular chondrocytes induced by gamma-interferon. Induction of Ia antigens

Immunotherapy in Rheumatoid Arthritis: A Review

The starting mode of the pathological process in rheumatoid arthritis (RA) is the presentation of an unknown ‘rheumatoid’ antigen by an antigen presenting cell to the receptor on the CD4+ T cell. The activation of the CD4+ T cell, and consequently of the cytokine network, is the second step in the inflammatory process.

Immunosuppression in RA, obtained using either immunosuppressive drugs (azathioprine, cyclophosphamide, methotrexate), or physical procedures (lymphoapheresis, total lymphoid irradiation) acts aspecifically on all lymphocyte populations, and can induce a number of side effects, such as myelotoxicity and opportunistic infections.

Two promising new therapeutic approaches are being developed, one aimed at specifically reducing the proliferation of activated T cell clones, and the second designed to modulate the activity of the cytokines involved in the inflammatory process. Encouraging results have been so far obtained with: a) cyclosporine A, a somewhat more specific immunosuppressive agent; b) monoclonal antibodies against surface antigens (CD4, CDS, CD7, CD25, CD54) expressed on activated T cells; c) T cell vaccination; and finally (iv) recombinant cytokines, their agonists or antagonists. Besides their utility in the treatment of the disease, these new therapeutical procedures should also lead to a better understanding of pathological processes in RA.

Alloreactivity and immunosuppressive properties of articular chondrocytes from osteoarthritic cartilage

PURPOSE

To determine whether articular chondrocytes derived from osteoarthritic knee joints could evoke alloreactive proliferation of peripheral blood mononuclear cells (PBMC) and inhibit mitogenic activity of polyclonally activated CD4+ major histocompatibility complex (MHC) class II- restricted T cells in vitro.

METHODS

Osteoarthritic cartilages of 17 patients aged 61 to 85 years were harvested during total knee arthroplasty. Chondrocytes were cultured for experiments. PBMCs, CD4+ T cells, CD8+ T cells, and CD14+ monocytes from healthy subjects were also used. To investigate the allogeneic response and immunosuppressive properties of chondrocytes, assays for one-way mixed lymphocyte reaction (MLR), apoptosis, activated CD4+ T-cell proliferation, and cytotoxic CD8+ T-cells were performed. Chondrocyte cell-surface antigens were examined using flow cytometry.

RESULTS

Chondrocytes failed to trigger an allogeneic PBMC reaction and did not induce apoptosis of allogeneic PBMCs in the MLR assay. Chondrocytes inhibited the proliferation of polyclonally activated CD4+ T cells via cell-cell contact and escaped the allogeneic cytotoxic reactivity of CD8+ T cells. Chondrocytes expressed MHC class I but not MHC class II molecules or B7-1/-2-positive co-stimulatory molecules.

CONCLUSION

Chondrocytes from osteoarthritic knees in older patients exhibited similar immunomodulatory properties in vitro to those in juveniles or adults.

ICAM-1 expression on chondrocytes in rheumatoid arthritis: induction by synovial cytokines

The intercellular adhesion molecule-1 (ICAM-1) was found by immunostaining chondrocytes in cartilage from three patients with rheumatoid arthritis. Expression of ICAM-1 was restricted to chondrocytes in areas of erodedcartilage adjacent to the invading synovial tissue. Toluidine blue staining of these areas demonstrated severe depletion of the cartilage extracellular matrix. In areas of undamaged cartilage there was no ICAM-1 expression. Since ICAM-1 is not constitutively expressed on normal human articular cartilage, but could be induced in vitro by exogenous IL-1alpha, TNFalpha and IFNgamma or by co-culturing cartilage with inflammatory rheumatoid synovium, we conclude that the induction of ICAM-1 on rheumatoid chondrocytes results from the synergistic action of a variety of cytokines produced by the inflammatory cells of the invading pannus.

Human articular chondrocytes express ChemR23 and chemerin; ChemR23 promotes inflammatory signalling upon binding the ligand chemerin(21-157)

Introduction

Chemerin is a chemotactic peptide which directs leukocytes expressing the chemokine-like receptor ChemR23 towards sites of inflammation. ChemR23 is a G protein-coupled receptor which binds several different ligands, and it is also expressed by other cell types such as adipocytes. In addition to chemotaxis, recent reports suggest that ChemR23 is capable of mediating either inflammatory or anti-inflammatory effects, depending on the type of ligand it binds. In the present study, we aimed to clarify whether human chondrocytes express ChemR23 and chemerin, and whether chemerin/ChemR23 signalling could affect secretion of inflammatory mediators.

Methods

Tissue sections were taken from human knee joints and labelled with antibodies towards chemerin and ChemR23. Chondrocytes from cartilage tissue were isolated, cultured and assessed for chemerin and ChemR23 expression by PCR and immunolabelling. Receptor activation and intracellular signalling were studied by assessment of phosphorylated mitogen activated protein kinases (MAPKs) and phosphorylated Akt after stimulating cells with recombinant chemerin^21-157. Biological effects of chemerin^21-157 were investigated by measuring secretion of pro-inflammatory cytokines and metalloproteases in cell supernatants.

Results

Both serially cultured human articular chondrocytes and resident cells in native cartilage expressed chemerin and ChemR23. Stimulating cells with chemerin^21-157 resulted in phosphorylation of p44/p42 MAPKs (ERK 1/2) and Akt (Ser 473). Also, significantly enhanced levels of the pro-inflammatory cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), tumour necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and the matrix metalloproteases MMP-1, MMP-2, MMP-3, MMP-8 and MMP-13 were detected.

Conclusions

These results demonstrate that human chondrocytes express both the receptor ChemR23 and the ligand chemerin. Chemerin^21-157 stimulation engaged signal-transduction pathways that further promoted inflammatory signalling in chondrocytes, as judged by an enhanced secretion of cytokines and metalloproteases. Taken together, the previously reported chemotaxis and the present findings suggest that the receptor and its ligand may play pivotal roles in joint inflammation.

In vitro characterization of immune-related properties of human fetal bone cells for potential tissue engineering applications

We describe herein some immunological properties of human fetal bone cells recently tested for bone tissue-engineering applications. Adult mesenchymal stem cells (MSCs) and osteoblasts were included in the study for comparison. Surface markers involved in bone metabolism and immune recognition were analyzed using flow cytometry before and after differentiation or treatment with cytokines. Immunomodulatory properties were studied on activated peripheral blood mononuclear cells (PBMCs). The immuno-profile of fetal bone cells was further investigated at the gene expression level. Fetal bone cells and adult MSCs were positive for Stro-1, alkaline phosphatase, CD10, CD44, CD54, and beta2-microglobulin, but human leukocyte antigen (HLA)-I and CD80 were less present than on adult osteoblasts. All cells were negative for HLA-II. Treatment with recombinant human interferon gamma increased the presence of HLA-I in adult cells much more than in fetal cells. In the presence of activated PBMCs, fetal cells had antiproliferative effects, although with patterns not always comparable with those of adult MSCs and osteoblasts. Because of the immunological profile, and with their more-differentiated phenotype than of stem cells, fetal bone cells present an interesting potential for allogeneic cell source in tissue-engineering applications.

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.

Involvement of the peripheral benzodiazepine receptor in the development of rheumatoid arthritis in Mrl/lpr mice

In this study, the effects of different peripheral benzodiazapine receptor ligands: PK 11195 [1-(2-chloro-phenyl)-N-methyl-N-(1-methylpropyl)-1-isoquinoline carboxamide], Ro5-4864 [7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one] and the newly described SSR 180575 (7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridozine[4,5-b] indole-1-acetamide) were analysed on the progression and severity of rheumatoid arthritis in vivo in the Mrl/lpr mice model, following chronic treatment (at 3 mg/kg, i.p. for 30 days). We found that peripheral benzodiazepine receptor ligands have significant beneficial therapeutic action on the development of spontaneous rheumatoid arthritis-like signs. Concomitantly, we mapped immunoreactive peripheral benzodiazepine receptor in inflamed tissues, and we observed that in addition to the infiltrated leukocytes, peripheral benzodiazepine receptor was expressed in synovial membranes, at the cartilage pannus junction and in chondrocytes. Interestingly, we observed that peripheral benzodiazepine receptor expression in chondrocytes was reduced when Mrl/lpr mice developed the pathology and restored upon peripheral benzodiazepine receptor ligand treatment. Altogether, our data provide further evidence of a role played by peripheral benzodiazepine receptor in the regulation of inflammation processes and support new therapeutic applications for specific potent peripheral benzodiazepine receptor ligands.

Immune response by host after allogeneic chondrocyte transplant to the cartilage

Chondrocytes constitutively express class I and, in some species, class II major histocompatibility complex (MHC). It is also possible that they possess specific differentiation antigen(s). Furthermore, lymphocytic cells, corresponding to NK cells, display spontaneous cytotoxic activity against chondrocytes. Studies on articular cartilage repair by transplants of allogeneic chondrocytes were mainly done on non-inbred animals, such as rabbits and hens. Surprisingly, only in single instances these transplants were rejected. In inbred rats, allogeneic chondrocytes transplanted into full-thickness defects in articular cartilage immediately after isolation evoked systemic immunological reaction and produced cartilage was rejected. Combined immunosuppression with cyclosporin A and cladribine did not prevent rejection of such transplants. Mechanical separation of transplants from bone marrow prevented sensitization of recipients and rejection of the produced cartilage. Successful allogeneic chondrocyte transplants in rabbits and hens could be tentatively explained by a certain degree of inbreeding among experimental animals, by the use of chondrocytes cultivated before grafting in artificial scaffolds and thus protected by matrix produced in vitro, and also by creation of a temporary mechanical barrier between transplant and bone marrow by tissues damaged during preparation of the defect.

Randomized, double-blind trial of anti-interferon-gamma antibodies in rheumatoid arthritis

INTRODUCTION

An increasing body of evidence indicates that interferon (IFN )-gamma is an immunoregulator and may play a key role in the pathogenesis of autoimmune diseases, including rheumatoid arthritis (RA).

OBJECTIVE

To assess the efficacy and tolerability of anti-IFN-gamma in patients with active RA.

METHODS

In a randomized, double-blind trial, 30 patients with active RA were randomly assigned to receive intramuscular injections of anti-IFN-gamma, anti-TNF-alpha, or placebo for 5 consecutive days.

RESULTS

Both anti-cytokines were significantly superior to placebo. Patients stopping treatment due to lack of efficacy included I receiving anti-TNF-alpha, 2 receiving anti-IFN-gamma, and 9 receiving placebo. According to the physician's assessment, improvement was achieved by the 7th day in 9 patients receiving anti-TNF-alpha, 7 receiving anti-IFN-gamma, and 2 receiving placebo. By day 28 the corresponding figures were 8, 8, and 0, respectively.

CONCLUSION

Antibodies to IFN-gamma could be a promising approach to treating RA, especially its treatment-resistant forms.

Proinflammatory cytokines detectable in synovial fluids from patients with temporomandibular disorders

OBJECTIVE

To measure the levels of the proinflammatory cytokines, interleukin (IL)-1 beta, IL-6, tumor necrosis factor- (TNF) alpha, IL-8, and interferon- (IFN) gamma in synovial fluid samples taken from patients with temporomandibular disorders (TMD).

STUDY DESIGN

We studied 6 asymptomatic volunteers and 51 patients with TMD. The IL-1 beta, IL-6, TNF-alpha, IL-8, and IFN-gamma levels in temporomandibular joint synovial fluid were measured using enzyme-linked immunosorbent assay.

RESULTS

Measurable level of at least one cytokine in the synovial fluid was found in 40 (64.5%) of 62 joints in the patients: IL-1 beta and IFN-gamma were each detected in 18 (29.0%) of 62 joints; IL-6 in 13 (21.0%) of 62 joints; IL-8 in 11 (19.3%) of 57 joints; and TNF-alpha in only 5 (8.1%) of 62 joints. None of these cytokines was detectable in the synovial fluid in the control group. Furthermore, there was a strong correlation between the detection of IL-1 beta and pain in the joint area.

CONCLUSIONS

These data clearly demonstrate increased levels of several proinflammatory cytokines in certain patients with TMD and suggest that these cytokines may play a role in the pathogenesis of synovitis and degenerative changes of the cartilaginous tissue and bone of the temporomandibular joint.

Analysis of heat shock proteins and cytokines expressed during early stages of osteoarthritis in a mouse model

OBJECTIVE

Osteoarthritis (OA) is a debilitating disease of the joints. The joints of affected individuals are characterized by a progressive degeneration of articular cartilage leading to inflammation and pain. The expression of heat shock proteins (HSPs) is a ubiquitous self-protective mechanism of all cells under stress, furthermore, the synovium of osteoarthritic individuals contains high levels of cytokines. This study seeks to establish the role of HSPs and cytokines in OA.

METHODS

We have investigated the presence of HSPs and cytokines in articular cartilage during early stages of OA in a mouse that is known to develop spontaneous OA lesions (C57 black mouse). The articular cartilage from closely related mice (C57BL/6) was used as control. Messenger RNAs (mRNAs) for HSPs (HSP32, HSP47, HSP60, HSP70, HSP84 and HSP86) and cytokines [interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma)] were detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The mRNA levels of HSP47, HSP70, HSP86, IL-6, and IFN-gamma were up-regulated in the cartilage of C57 black mice, whereas, the level of expression of HSP32, HSP60, HSP84 and IL-1 beta remained unchanged. Furthermore, the expression of IL-1 beta, IL-6, TNF-alpha and IFN-gamma mRNA was associated with expression of HSP60, HSP47, HSP70 and HSP70/HSP86 mRNA, respectively.

CONCLUSIONS

The findings in this study suggest that chondrocytes are conditioned under non-physiological stress during early stages of OA, In addition, among HSPs, HSP70 was associated with two different highly expressed cytokines in C57 black mice, indicating the possible role of HSP70 as a characteristic indicator of early stage of OA.

Monoclonal antibodies against human chondrocytes

Cell-specific antigens are mainly found in cells or membrane surfaces rather than in the surrounding matrix. However, until now it was not possible to produce antibodies specific for cellular structures of chondrocytes. In 1989, Lance (Immunol. Lett. 21:63-73; 1989) first established specific monoclonal antibodies for human articular chondrocytes tested only by immunofluorescence. Studies describing the specificity of these five antibodies (HUMC 1-5) and their relevance for immunohistological analysis of cartilage tissue were not available until now. Therefore, the aim of the following study was to investigate the distribution of HUMC 1, 2, 3, 4, and 5 in mesenchymal cells in vivo and in vitro immunohistochemically. Further investigations concentrate on the localization of chondrocyte specific antigens using immunoelectron microscopy. Immunohistological studies showed positive immunostainings with all five antibodies in human chondrocytes in vivo and in vitro. A cross-reaction with human fibroblasts and osteoblasts for the antibodies HUMC 2 and HUMC 5 was observed. Furthermore, a parallel loss of immunoreactivity for HUMC 1, HUMC 3, and HUMC 4 was observed in cultured chondrocytes indicating that the specific antigens vanish during differentiation observed in vitro. Subsequent immunoblot analysis employing collagens as antigens did not show any reactivity. Using immunoelectron microscopy, gold particle labeling was observed in intracytoplasmatic vesicles of isolated chondrocytes. Our results indicate that HUMC 1, HUMC 3, and HUMC 4 are specific for cartilage cells and might be suitable for immunohistological analysis of different cartilage tissues and pathologically altered chondrocytes.

Expression of ICAM-1 on intact cartilage and isolated chondrocytes

A major factor in cellular cytotoxicity is the interaction between LFA-1 on leukocytes and ICAM-1 on targets. Because several inflammatory cartilage diseases are characterized by the presence of leukocyte infiltrates, the expression of ICAM-1 on human cartilage, cultured chondrocytes, and transplanted cartilage was investigated using monoclonal antibodies. Frozen tissue sections, chondrocytes in suspension, as well as total cellular mRNA were prepared from human cartilage samples. ICAM-1 expression was studied with two different monoclonal antibodies directed against ICAM-1 by immunohistochemical APAAP-staining and additional flow cytometric analyses. The expression of ICAM-1-mRNA in cartilage tissue was analyzed using the northern blot hybridization technique. Furthermore, chondrocytes were treated in culture with interleukin-1 (IL-1) and gamma-interferon (gamma-IFN). ICAM-1 expression after culture was quantified using flow cytometric analysis. We could detect ICAM-1 mRNA in cartilage tissue, however, the immunostaining of tissue sections using monoclonal antibodies did not give clear positive reactions. Isolated chondrocytes showed strongly positive staining patterns in comparison with adequate negative controls as assessed by flow cytometry. A dose-dependent increase of the expression of ICAM-1 on chondrocytes was observed when stimulated with IL-1 and gamma-IFN. Finally, two of the three studied transplanted autologous cartilage samples with advanced resorption showed the presence of ICAM-1 molecules as assessed by immunohistochemistry. This expression of ICAM-1 suggests that the molecule plays a role in severe cartilage inflammatory processes, where tissue damage leads to the exposure of chondrocyte surfaces.

Rejection of cartilage formed by transplanted allogeneic chondrocytes: evaluation with monoclonal antibodies

Cellular infiltrates participating in rejection of cartilage formed by transplanted allogeneic rat epiphyseal chondrocytes were evaluated immunohistochemically using a panel of different monoclonal antibodies. One week after transplantation, the grafts were surrounded by numerous class II MHC+ (OX6+, OX17+), CD4+ (W3/25+), and W3/13+ cells as well as some ED1+ monocytes/macrophages. Only a few T (OX19+) and B (HIS14+) cells were present. The number of class II MHC+ cells and ED1+ monocytes/macrophages did not change significantly in the course of rejection whereas the number of CD4+ and W3/13+ cells gradually decreased. On the other hand, there was a significant increase in the number of CD8+ (OX8+) cells. CD8+ cells accumulated close to the transplants and some of them penetrated cartilage matrix suggesting that they might be involved in chondrocyte killing. After 3 months, cartilage was almost completely destroyed and the intensity of infiltrations was markedly decreased. Fibrous connective tissue predominated, however, some class II+ as well as few ED1+, CD4+ and CD8+ cells were still present adjacent to the cartilage remnants. At the time of transplantation, chondrocytes were endowed with RT1.D class II antigen (OX17+), but they did not react with OX6 mAb (monoclonal antibody) recognizing the RT1.B class II molecule. However, after 1 week, some chondrocytes reacted with OX6 mAb and the number of RT1.B positive chondrocytes increased in the course of cartilage rejection.

Interferon-gamma but not granulocyte/macrophage colony-stimulating factor augments proteoglycan presentation by synovial cells and chondrocytes to an autopathogenic T cell hybridoma

Immunization of BALB/c mice with human cartilage proteoglycan (aggrecan) produces a progressive polyarthritis, similar in many aspects to human rheumatoid arthritis, and autoreactive T cells are necessary for initiation of the disease. To study the immunopathological mechanisms operating in the synovium of arthritic mice, we isolated a proteoglycan (PG)-specific arthritogenic T-cell hybridoma, 5/4E8, and examined the presentation of PG to this T-cell hybridoma by mouse synovial cells and chondrocytes. Both cell types expressed very low levels of major histocompatibility complex (MHC) class II following isolation and culture and were unable to present PG to the hybridoma. However, following stimulation with interferon-gamma (IFN-gamma), both synovial cells and chondrocytes showed a marked increase in MHC class II expression and consequently were able to present PG very effectively. The PG-specific responses of the hybridoma were abrogated by an anti-Ia monoclonal antibody. Granulocyte-macrophage colony-stimulating factor (GM-CSF), one of the most abundant cytokines in the rheumatoid synovium, had no effect on the antigen-presenting capacity of synovial cells and chondrocytes, either on its own or together with IFN gamma.

Antigen presenting cell function of class II positive human nasal chondrocytes

It is postulated that class II positive chondrocytes may be actively involved in the destruction or rejection of vital transplanted cartilage grafts. To investigate whether human nasal chondrocytes may also function as accessory cells in ongoing immune reactions with cartilage destruction, mixed leukocyte-chondrocyte cultures and antigen presentation assays were performed. Freshly isolated HLA class II antigen negative chondrocytes obtained from nasal septa were not stimulatory to autologous resting T lymphocytes. HLA class II positive chondrocytes treated with gamma-interferon were able to present antigens to autologous activated T cells derived from an antigen (tetanus) specific T cell line. Upon incubation with activated T cells, initially class II negative changed their phenotype resulting in the expression of class II antigens and enabling them to effectively present antigen. These results suggest an active role of chondrocytes in the rejection of cartilage grafts.

Expression of ICAM-1 on isolated human nasal, auricular and costal chondrocytes

Expression of intercellular adhesion molecule-1 (ICAM-1) on targets has been reported to be a relevant factor for leukocyte migration, adhesion and function. Because stimulated chondrocytes have been shown to express molecules of immunological import (like HLA class II antigens) and because rejected or resorbed cartilage grafts used in the field of ENT are often characterized by adjacent infiltrating leukocytes, the presence of ICAM-1 on human nasal, auricular and costal cartilage was investigated. For this study, cartilage tissue sections and chondrocytes in suspension as well as cultured chondrocytes were prepared. Specific monoclonal antibodies (mAb) were used for immunocyto- and immunohistochemical Alkaline-Phosphatase-anti-Alkaline-Phosphatase staining (APAAP staining) as well as for flow cytometry analysis. ICAM-1 on healthy cartilage tissue sections was not found. On the other hand, both chondrocytes freed from matrix and cultured chondrocytes showed strongly positive staining patterns for ICAM-1. This result was obtained for chondrocytes from nasal, auricular as well as costal cartilage. This observed expression of ICAM-1 on chondrocytes with defective extracellular matrix demonstrates that cartilage cells are able to synthesize ICAM-1 without any paracrine stimulus from non-chondrocyte cells. It suggests that ICAM-1 plays a role in processes where tissue damage leads to the exposure of chondrocyte surfaces. Therefore, ICAM-1 expression on chondrocytes may also be a factor in destructive cartilage graft resorption.

Enhanced chondrocyte destruction by lymphokine-activated killer cells. Possible role in rheumatoid arthritis

OBJECTIVE

The lysis of chondrocytes, the parenchymal cells of cartilage, by lymphocytes may provide a potent mechanism by which the immune system participates in sustaining joint damage in rheumatoid arthritis (RA). We studied the capability of lymphocytes from healthy individuals and patients with arthritis to lyse chondrocytes.

METHODS

Peripheral blood mononuclear cells (PMBC) were tested for their ability to lyse chondrocytes in a 51Cr-release assay. Enhancement of the chondrolytic activity was determined by preincubating the cells with T cell growth factor (TCGF) or recombinant interleukin-2 (rIL-2) before cytotoxic testing.

RESULTS

PBMC from healthy individuals possessed a low ability to lyse chondrocytes, whereas cells from the synovial fluid of patients with RA displayed higher chondrolytic activity. In RA, modulating factors must come into play because not all synovial fluid sample cells showed high chondrolytic activity and cells from synovial tissue had little or no lytic action on chondrocytes. Chondrolytic activities of cells from all sources, including PBMC from healthy subjects and patients with arthritis and cells isolated from synovial fluid or from the synovial tissue of RA patients, were greatly increased by incubating the cells with TCGF or rIL-2. In contrast, treatment of chondrocytes with interferon-gamma, which enhances major histocompatibility complex gene expression, decreased the susceptibility of chondrocytes to lysis.

CONCLUSION

These observations suggest a mechanism for joint damage in which the destruction of chondrocytes by lymphocytes is controlled by cytokines released during the inflammatory process in arthritic diseases.

Differential induction of stromelysin mRNA by bovine articular chondrocytes treated with interferon-gamma and interleukin-1 alpha

Articular chondrocytes from rheumatoid joints have been shown to express class II major histocompatibility (MHC) antigens that were correlated with the presence of interferon-gamma (IFN-gamma) in the inflamed joint. Chondrocytes expressing MHC antigens function as antigen presenting cells and thus stimulate lymphocyte proliferation. These responses suggest a powerful role for the IFN-gamma stimulation of chondrocytes. The present studies were designed to examine the functional role of chondrocytes exposed to IFN-gamma during cartilage degradation that occurs in synovial disease. Destruction of cartilage in arthritis is partially attributable to metalloproteinases released by the chondrocytes in response to interleukin-1 (IL-1). Bovine articular chondrocytes treated with interleukin-1 alpha (IL-1 alpha) produced enhanced levels of stromelysin mRNA, however, Northern blots could not determine the percentage of cells responding. Exposure of bovine articular chondrocytes to IFN-gamma induced the expression of bovine HLA-DR (boHLA-DR) antigen in 50% of the cells. Using a modified cell sorting technique, chondrocytes that expressed class II MHC antigens produced two fold greater stromelysin mRNA than chondrocytes that did not express this antigen. In contrast, collagen type II mRNA levels were similar in chondrocytes, regardless of the expression of class II MHC antigens. In situ hybridization studies showed that less than half of all cartilage chondrocytes were induced to synthesize stromelysin mRNA. These observations suggest that IFN-gamma stimulates specific subpopulations of chondrocytes to be functionally active in inflammation-induced metalloprotease secretion.

Cellular responses to human chondrocytes: absence of allogeneic responses in the presence of HLA-DR and ICAM-1

To assess the accessory cell function of human articular chondrocytes, we assessed the ability of human chondrocytes to stimulate allogeneic peripheral blood mononuclear cells (PBMC) and to support phytohaemagglutinin (PHA)-induced proliferation of highly purified T cells. We also examined the surface expression of HLA-DR and ICAM-1 on the chondrocytes both unstimulated and stimulated with cytokines in vitro. Chondrocytes failed to stimulate allogeneic PBMC despite the constitutive expression of MHC class I molecules and the cytokine-induced expression of class II molecules but were able to support T cell proliferation to PHA, IFN-gamma and to a limited extent, IL-1 beta, induced class II expression on chondrocytes. ICAM-1 was present on 94-99% of freshly isolated cells; this declined with culture (17-59%; P < 0.005) but was readily induced by IFN-gamma, IL-1 beta, and tumour necrosis factor-alpha. Alloreactivity and, presumably, autoreactivity to chondrocytes requires factors in addition to the surface expression of DR and ICAM-1. However the presence of these molecules suggests a capacity for cell-cell interactions in inflammatory sites such as the cartilage pannus junction.

Decreased monocyte-mediated angiogenesis in scleroderma

Scleroderma is a disease characterized by proliferative vascular lesions in which monocytes/macrophages may play a key role. Monocytes were isolated from 14 scleroderma patients and 11 normal controls and cultured with or without lipopolysaccharide (LPS) (5 micrograms/ml). Monocyte-conditioned medium was assayed in the rat corneal bioassay for angiogenesis. Conditioned medium from normal monocytes was nonangiogenic, as was conditioned medium from scleroderma monocytes. While conditioned medium from LPS-activated normal monocytes was potently angiogenic in 11/13 corneas, conditioned medium from LPS-activated scleroderma monocytes was angiogenic in only 3/14 corneas. Levels of the angiogenic cytokine tumor necrosis factor-alpha (TNF-alpha) were measured in conditioned medium from scleroderma and normal monocytes. TNF-alpha levels were not significantly different in patient and control groups and thus do not account for the decreased angiogenic activity exhibited by scleroderma monocytes. As monocytes require activation to produce angiogenic activity, we determined the cell surface binding of monoclonal antibodies to activation-related (HLA-DR, 3D8, and 8D7) and other (Leu-M5) markers on monocytes by radioimmunoassay. Monocytes were cultured alone, with LPS (5 micrograms/ml), or with interferon-gamma (IFN) (200 units/ml). The usual increase in binding of anti-HLA-DR on stimulation of scleroderma monocytes with IFN was slightly less than that of controls. IFN-stimulated monocytes bound less anti-8D7 than controls. Anti-3D8 and anti-Leu-M5 binding was comparable in both groups. These results suggest that scleroderma monocytes do not produce normal levels of angiogenic activity with LPS stimulation, have some altered markers of activation on their cell surfaces, and may thus contribute to the aberrant vascular proliferation found in this disease.

A monoclonal antibody to the mycobacterial 65 kDa heat shock protein (ML 30) binds to cells in normal and arthritic joints of rats

A monoclonal antibody reactive with the mycobacterial 65 kDa heat shock protein (ML 30) was investigated for reactivity with biopsies from normal rat joints and with inflamed joints due to adjuvant arthritis (AA) or collagen induced arthritis (CIA). Immunohistochemical stainings with the anti-hsp 65 antibody on paraffin sections from normal rat joints revealed a weak but exclusive staining of cells within the synovial lining. Also normal chondrocytes and bone marrow cells showed occasional staining. In biopsies from inflamed joints obtained from rats suffering from AA or CIA, an intense staining with ML 30 was seen within the cartilage-pannus junction as well as sites of bone erosion. An increased staining, compared with the normal, was also seen in chondrocytes of the eroded cartilage and in some bone marrow cells. No staining with ML 30 was seen in biopsies from inflammatory lesions due to delayed type hypersensitivity reactions in the skin of rats. Reactivity of ML 30 was also seen in a Western blot assay performed on lysates from inflamed synovia from rats with CIA, preferentially with a component slightly below 60 kDa in molecular weight. The demonstration of epitopes cross-reactive with hsp 65 of mycobacteria in normal and, in higher quantity, in arthritic rat joints, suggests, together with our preliminary biochemical findings, that a recently identified mammalian counterpart to bacterial hsp 65 is both preferentially expressed in normal joints and subject to increased expression in arthritis of different aetiologies.

Control of the expression of a class II major histocompatibility gene (HLA-DR) in various human cell types: down-regulation by IL-1 but not by IL-6, prostaglandin E2, or glucocorticoids

We have examined the effects of recombinant human IL-1 alpha and IL-1 beta on expression of the gene for the class II major histocompatibility antigen, HLA-DR, and the class I MHC antigen, HLA-B7, induced by natural or recombinant human IFN-gamma in several human cell types. Recombinant hIL-1 alpha and hIL-1 beta antagonized the class II MHC-inducing effect of IFN-gamma in human monocytes and normal skin fibroblasts, and in chondrosarcoma and astrocytoma cell lines. In the presence of IL-1 alpha or IL-1 beta, the induction by IFN-gamma of HLA-DR mRNA, and the expression of the corresponding antigen on the cell surface, were reduced when analysed by dot-blot hybridization and flow cytometry respectively. Nuclear transcription assays showed that IFN-gamma augmented expression of the HLA-DR gene and that IL-1 alpha inhibited this effect. IL-1-mediated inhibition was not observed with IFN-gamma-induced expression of MHC class I mRNA (HLA-B7). Both IL-1 alpha and IL-1 beta induced production of IL-6 mRNA and of PGE2 in these cell types. However, recombinant IL-6 or PGE2 did not inhibit IFN-gamma-induced HLA-DR mRNA expression. Dexamethasone did not inhibit HLA-DR expression in the cells studied but eliminated the inhibitory effect of IL-1 on such expression. The observations suggest that MHC gene expression is influenced by the cytokine network in a complex manner which is different for class I and II genes. Glucocorticoids and PGE2 do not consistently inhibit class II expression.

Role of cytokines in inflammatory synovitis. The coordinate regulation of intercellular adhesion molecule 1 and HLA class I and class II antigens in rheumatoid synovial fibroblasts

This study was undertaken in an effort to understand the role of cytokines in T lymphocyte trafficking into inflamed synovium and in the potential enhancement of antigen presentation by human synovial fibroblasts. We found that interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), and interferon-gamma (IFN gamma) each increased the cell surface expression of intercellular adhesion molecule 1 (ICAM-1) on human synovial fibroblasts in a dose- and time-dependent manner. Maximal ICAM-1 expression occurred within 8 hours of induction, with the following order of efficacy: IFN gamma greater than TNF alpha greater than IL-1 beta. The number of cells bearing the ICAM-1 antigen also increased, from a basal level of approximately 30% to more than 83% after cytokine induction (for all 3 cytokines). ICAM-1 expression rapidly decreased following cytokine removal. The expression of lymphocyte function-associated antigen 3 was also examined, but it was not changed by any of the 3 cytokines. Class I major histocompatibility complex antigen expression was increased modestly by all 3 cytokines, and expression was maximal by 24 hours after treatment. Only IFN gamma induced HLA class II antigen expression, and this expression persisted for up to 6 days following removal of the lymphokine. IL-6 and granulocyte-macrophage colony-stimulating factor had no effect on any of the parameters examined. Our data support an interactive role for inflammatory cytokines and the expression of adhesion ligands and HLA antigens by human synovial fibroblasts in the pathogenesis of synovial inflammation in rheumatoid arthritis.

Inhibition of interleukin-1-induced collagenase production in human articular chondrocytes in vitro by recombinant human interferon-gamma

The production of collagenase by human articular chondrocytes in response to interleukin-1 beta is inhibited in a dose-dependent manner by interferon-gamma (1-1,000 units/ml). The analysis of culture medium samples by Western blotting and the measurement of levels of tissue inhibitor of metalloproteinases suggest that the decrease in measurable collagenase activity is primarily due to the inhibition of procollagenase production. These results provide evidence of a role for interferon-gamma in limiting connective tissue degradation.

Cellular immune response toward human articular chondrocytes. T cell reactivities against chondrocyte and fibroblast membranes in destructive joint diseases

Articular cartilage is one of the major targets in destructive joint diseases in humans. We studied cellular immune reactions against cartilage cell-surface membranes, because it has recently been suggested that these represent possible antigenic structures, based upon the observation of autoantibodies with this specificity in certain joint diseases. A striking T cell reactivity toward chondrocyte membranes was found both in blood and synovial tissue from patients with rheumatoid arthritis. This reactivity was strongly dependent on the presence of monocytes and had all the characteristics of an antigen-driven process. Clonal analysis demonstrated high precursor frequencies in peripheral blood T cells that were reactive against chondrocyte membranes. This response to chondrocyte membranes greatly exceeded the T cell stimulation induced by membranes from other sources such as fibroblasts or epithelial cells. In contrast to patients with rheumatoid arthritis, individuals with osteoarthritis showed a strong peripheral blood and synovial fluid T cell response not only to chondrocyte membranes, but also to fibroblast membrane material. However, there was no reactivity to epithelial cell membranes. Normal donors generally did not show significant responses to any membrane preparation. These data indicate that there is a strong T cell reactivity toward chondrocyte membranes in destructive joint disorders, and this may significantly contribute to the pathogenetic processes that occur in these diseases.

The effect of gamma-interferon on HLA class II antigen expression on isolated human nasal chondrocytes

HLA class II antigens play an important role in the immunological response. In this study, we report on HLA class II antigen expression in vitro by human nasal cartilage cells as detected with an immunoperoxidase staining and immunofluorescence flow cytometric analysis using monoclonal antibodies. Their expression was induced during a 7-day incubation period with gamma-interferon. These findings suggest that a possible mode of action of the preservation methods of cartilage allografts for inducing a prolonged acceptance time is based on the prevention of HLA class II antigen expression by the cartilage cells.

Constitutive and inducible expression of HLA class II determinants by human osteoblast-like cells in vitro

Activated immune cells release cytokines which modulate the activity of bone cells in vitro. Expression of major histocompatibility complex (HLA in humans) class II determinants on bone surface cells may be important in local immune cell activation. In this study, expression of HLA-DR and DQ by cultured human bone cells (HBC) derived from normal trabecular bone surfaces was assessed by fluorescence-activated cell sorter (FACS) analysis and immunoperoxidase techniques using monoclonal antibodies. A subset of HBC (10-30%) expressed DR constitutively while 5-15% displayed DQ during long-term culture. HBC lacked a number of monocyte and lymphocyte markers. In addition, both DR+ and DR- HBC (FACS separated) produced osteocalcin stimulated by 1,25-dihydroxyvitamin D2 (1,25(OH)2D3). This suggests that both phenotypes belong to the osteoblast lineage. The number of DR+ HBC was increased by interferon-gamma (IFN gamma; 40-95% DR+ cells) whereas DQ+ HBC remained unchanged or was slightly increased (5-20% DQ+ cells). Moreover, 1,25(OH)2D3 enhanced IFN gamma-induced DR expression and at high concentration (10(-7) M) augmented DR expression by itself. Other major osteotropic factors, parathyroid hormone, interleukin 1, and calcitonin, did not affect HBC DR expression. The findings suggest that HBC may participate in activation of the immune system and that some osteotropic factors may regulate this function.

Cytokines in chronic inflammatory arthritis. III. Rheumatoid arthritis monocytes are not unusually sensitive to gamma-interferon, but have defective gamma-interferon-mediated HLA-DQ and HLA-DR induction

Macrophages present in the synovium and synovial fluid of patients with rheumatoid arthritis (RA) express large amounts of HLA-DR molecules on their surface, despite low levels of gamma-interferon (gamma-IFN) in the joint. To determine whether this apparent paradox is the result of increased sensitivity to gamma-IFN in RA, we compared concentrations of gamma-IFN that induced HLA-DR and DQ on peripheral blood monocytes of RA patients and normal donors, using fluorescence-activated cell sorter analysis. Among normal donors, highly variable sensitivity to gamma-IFN was observed. Higher amounts of gamma-IFN were required to induce class II major histocompatibility complex molecules on RA monocytes versus normal monocytes. The maximum amount of HLA-DR that could be induced on RA and normal monocytes was similar; however, peak levels of HLA-DQ were significantly less in RA. Monocytes from patients with other forms of chronic inflammatory arthritis had intermediate HLA-DQ expression after gamma-IFN treatment. These data suggest that an increased sensitivity to gamma-IFN in RA does not account for the high level of HLA-DR expression in the joint. Also, a defect in HLA-DQ and HLA-DR induction by gamma-IFN was observed.

Modulation of human chondrocyte metabolism by recombinant human interferon gamma: in-vitro effects on basal and IL-1-stimulated proteinase production, cartilage degradation and DNA synthesis

Human articular chondrocytes in monolayer culture and fragments of human articular cartilage were treated with recombinant human interferon gamma (IFN-gamma) both alone and in combination with interleukin 1 (IL-1). IFN-gamma alone inhibits metalloproteinase production, as measured in the caseinase assay, and decreases glycosaminoglycan release from cartilage fragments in culture. The synthesis of DNA, as measured by [3H]thymidine incorporation, is stimulated by IFN-gamma. Similar effects are seen in the presence of IL-1. Thus, IFN-gamma opposes the stimulatory effect of IL-1 on caseinase production and decreases IL-1-stimulated cartilage degradation, as measured by glycosaminoglycan release. In contrast, IFN-gamma has no effect on IL-1-stimulated prostaglandin production, and acts synergistically with IL-1 to cause a large stimulation of DNA synthesis. These results show that IFN-gamma has a number of effects on articular chondrocytes in-vitro and suggest a possible role for IFN-gamma in limiting cartilage degradation in inflammatory joint conditions.

The effect of tumor necrosis factor alpha and gamma-interferon on the resorption of human articular cartilage and on the production of prostaglandin E and of caseinase activity by human articular chondrocytes

In cultured human articular chondrocytes, addition of tumor necrosis factor alpha (TNF alpha) stimulated caseinase activity over the range of 10(-11) M to 10(-7) M and stimulated prostaglandin E (PGE) production over the range of 10(-10) M to 10(-7) M. Maximal stimulation was observed at 10(-8)M TNF alpha for both activities. Gamma-interferon (gamma-IFN) had a variable effect on PGE production and no significant effect on caseinase activity in articular chondrocyte cultures over a concentration range of 0.1-1,000 units/ml. Co-incubation of TNF alpha with gamma-IFN enhanced PGE production and decreased caseinase activity. Concentrations as low as 1 unit/ml of gamma-IFN had significant effects on TNF-stimulated production of PGE and on caseinase activity. Resorption of human articular cartilage was stimulated by TNF alpha (10(-7) M) and was inhibited by gamma-IFN (1,000 units/ml). It is possible that cartilage breakdown in vivo may be modulated by such interactions between cytokines.

Treatment with gamma-interferon triggers the onset of collagen arthritis in mice

We investigated the effect of gamma-interferon (gamma-IFN) on the development of type II collagen (CII)-induced arthritis. DBA/1 mice were immunized with rat CII and 16 days later, were treated with subcutaneous injections of recombinant rat gamma-IFN into the right paws twice a week. Compared with controls, the gamma-IFN-treated mice developed arthritis with a higher frequency and severity. Immunohistochemical analysis of gamma-IFN-treated paws from CII-immunized mice revealed an increase in the numbers of class II antigen-expressing cells and an infiltration of CD4+ lymphocyte-like cells. The auto-antibody response toward CII was suppressed by gamma-IFN treatment. The findings implicate gamma-IFN in a role that triggers arthritis by enhancing local inflammatory processes in the joints, or possibly, by permitting homing of T cells to the joints.

Premises for immune interventional therapy in rheumatoid arthritis

Consideration of rheumatoid arthritis (RA) as an autoimmune disease includes initiating event(s), genetic predisposition, immune regulatory derangements, and effector cycles of articular damage. The initiating event is still unknown. Collagen type 2 has good claims as a rheumatogenic autoantigen which perpetuates disease. The association of HLA DR4 with rheumatoid arthritis is in part explainable by the affinity of binding of the rheumatogenic antigen to a hypervariable portion of MHC Class II molecules with selective presentation of this complex to T cell receptors. Immune regulatory derangements include lymphokine-induced aberrant expression of MHC Class II molecules on synovial tissues, the presence of a 'resistant' subset of B cells (CD5 + ve), failure of anti-idiotypic control of autoantibodies (not well established as yet in rheumatoid arthritis), and defective immune suppression, revealed by low counts in synovial fluids of a suppressor-inducer subset of CD4 + ve T cells. The many possibilities for therapeutic immune intervention would include polyclonal or monoclonal antibody to block (a) receptors for antigen on B or T lymphocytes (but this would require knowledge of the rheumatoid arthritis-inducing antigen), (b) the CD4 complex on helper T lymphocytes, (c) MHC Class II (Ia) molecules, for which there are excellent prototypes in experimental immunopathology, or (d) lymphokines or their receptors. Induction of suppression by 'tolerogenic vaccines' is experimentally validated, but only for diseases for which an autoantigen can be identified.

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

In a multicenter placebo-controlled double-blind randomized clinical study, 91 patients with rheumatoid arthritis were given 28 days' treatment with recombinant interferon-gamma (50 micrograms daily for 20 days, then 50 micrograms each second day up to day 28, given by subcutaneous injection). The aim of the study was to provide a methodologically clear demonstration of the efficacy of treatment with interferon-gamma, using criteria that could be handled by statistical tests. Evaluatable documentation was available for 79 patients, of whom 40 were treated with the active compound. The principal criterion for the statistical evaluation of the therapeutic success was improvement of the Ritchie "joint pain index" or Lansbury "joint pain index" by at least 30% within 28 days. The chi-square test showed superiority of the interferon arm over the placebo arm with an error probability of alpha less than 1%. In addition, efficacy of interferon-gamma was demonstrated in respect of practically all parameters investigated. The frequency of side-effects, including febrile reactions, was the same for the active compound and the placebo. During interferon treatment the daily maximum body temperature was raised by 0.3 degrees C on average, but was below 37.2 degrees C at all times.

Differential expression of Ia antigens by rheumatoid synovial lining cells

The differential expression of Ia antigens was studied in freshly isolated rheumatoid nonlymphoid synovial lining cells (SLC) and rheumatoid synovial fibroblast cell lines cultured in the presence of Interferon-gamma, using a large panel of anti-Ia reagents with monomorphic or polymorphic specificities. All the HLA-DR or -DQ specificities detectable on the corresponding peripheral blood B cells were also expressed in freshly isolated SLC. However, in all instances, the number of DR-positive SLC exceeded the percentage of cells expressing DQ antigens. In addition, the epitope expression of Ia antigens varied within the DR or DQ populations of Ia molecules as revealed by polymorphic reagents. Double-label experiments or using the ingestion of Latex particles as a marker demonstrated that the synovial macrophages (type I SLC) primarily bear the DR+DQ+ phenotype, while there is an additional population of nonphagocytic SLC (previously termed type II SLC) that has a DR+ and monocyte marker negative phenotype but did not have detectable levels of DQ antigens as analyzed by both fluorescence microscopy and cell sorter analysis. This latter population frequently had a morphology showing dendritic processes and rapidly lost the expression of Ia antigens upon culture. Cells with a similar, primarily DR+ phenotype were readily obtained in synovial fibroblast cultures after treatment with Interferon-gamma. These data suggest that there are two populations of Ia+ synovial lining cells: the synovial macrophages (type I cells) with the DR+DQ+ phenotype, and cells probably related to fibroblasts with a DR+ phenotype without detectable DQ antigens (type II cells). The fact that the latter phenotype could be induced by Interferon-gamma treatment of cultured synovial fibroblasts suggests that this mediator may have a similar role in vivo in the activation of certain synovial cell populations.