Synovial membrane expression of matrix metalloproteinases and tissue inhibitor 1 in juvenile idiopathic arthritides

OBJECTIVE: Matrix metalloproteinases (MMP) are a large family of proteolytic enzymes involved in the remodeling of extracellular matrix during tissue resorption. We investigated synovial tissue expression of the main proteolytic enzymes (MMP-1, MMP-3, and MMP-13) and tissue inhibitor of metalloprotease 1 (TIMP-1) in juvenile idiopathic arthritides (JIA). METHODS: Expression of MMP-1, MMP-3, MMP-13, and TIMP-1 was studied by immunohistochemical analysis of synovial tissues, obtained at synoviectomy or arthroplasty from 9 patients with JIA, and was correlated with mononuclear cell infiltration into the lining layer. RESULTS: MMP-1 and MMP-3 were abundantly expressed in the lining layer, showing a high degree of correlation with macrophage infiltration (CD68+ cells). MMP-13 showed a lower degree of expression, with tissue distribution almost restricted to the sublining regions. TIMP-1 tissue distribution was similar to that observed for MMP-1 and -3, although with a definitely lower number of positive cells. CONCLUSION: The expression of MMP-1 and MMP-3 in the synovium of patients with IA was clearly correlated with the degree of inflammation. This indicates the possible role of MMP in the pathogenesis of synovitis in this group of pediatric idiopathic arthritides. Inadequate expression of tissue inhibitors may represent a crucial event for the development and perpetuation of tissue damage.     

Serum and synovial fluid concentration of vascular endothelial growth factor in juvenile idiopathic arthritides

OBJECTIVE: To evaluate the role of vascular endothelial growth factor (VEGF) in the pathogenesis of local joint inflammation in juvenile idiopathic arthritis (JIA). METHODS: Sera from 50 patients affected with JIA and 10 age-matched healthy controls were tested with a commercial ELISA for VEGF. Corresponding synovial fluid (SF) concentrations of VEGF and p75 soluble tumour necrosis factor receptor (sTNFR) were evaluated in 20 active JIA patients. RESULTS: Serum concentrations of VEGF were significantly higher in patients with active polyarticular disease than in patients with active and inactive oligoarticular disease and healthy controls. In JIA patients, serum concentrations of VEGF displayed a significant correlation with a number of clinical and laboratory parameters of disease activity. VEGF concentrations in SF were significantly higher than those detected in corresponding sera. Moreover, a clear correlation was found between corresponding SF and serum VEGF concentrations. In SF, VEGF showed a strong positive correlation with p75 sTNFR. CONCLUSIONS: Concentrations of VEGF in SF in patients with JIA are higher than corresponding serum concentrations, suggesting that this pro-angiogenic factor may have a major role in the outgrowth of hyperplastic pannus and tissue damage at the site of tissue inflammation.     

Interleukin 17 levels are increased in juvenile idiopathic arthritis synovial fluid and induce synovial fibroblasts to produce proinflammatory cytokines and matrix metalloproteinases

OBJECTIVE: Cytokines are the major mediators of joint damage in chronic arthritis. Data on synovial fluid (SF) concentration of Th17 cell-derived cytokine interleukin 17 (IL-17) in patients with juvenile idiopathic arthritis (JIA) are sparse. We measured levels of IL-17 in SF specimens from children with enthesitis-related arthritis (ERA) and polyarticular JIA (poly-JIA), and studied the ability of IL-17 to produce matrix metalloproteinases (MMP) and cytokines by fibroblast-like synoviocytes (FLS) from patients with ERA. METHODS: IL-17 levels were measured in SF of patients with ERA (n = 43), poly-JIA (n = 17), rheumatoid arthritis (RA; n = 35), and osteoarthritis (OA; n = 10) by ELISA. In patients with JIA, 10 paired serum samples were also assayed. FLS were cultured from SF of patients with ERA and subsequently stimulated for 48 h by IL-17 or tumor necrosis factor-alpha. Later the production of IL-6, IL-8, MMP-1, MMP-3, and tissue inhibitor of metalloproteinase (TIMP)-1 was measured in the culture supernatants by ELISA. RESULTS: Median IL-17 levels in SF were higher in patients with JIA [28 pg/ml (range 0-200)] compared to OA [0 pg/ml (range 0-84); p < 0.001] and RA (p < 0.05). The levels were comparable between poly-JIA patients and the ERA group. The median SF IL-17 levels were significantly higher compared to serum levels in children with JIA (p < 0.005). In ERA, SF IL-17 correlated with number of swollen joints (r = 0.35; p < 0.05), number of joints with limited mobility (r = 0.55; p < 0.001), and number of tender joints (r = 0.46; p < 0.01); however, no correlation was seen with erythrocyte sedimentation rate. IL-17 induced FLS to produce IL-6, IL-8, MMP-3, and MMP-1. However, there was no effect on the production of TIMP. CONCLUSION: Increased IL-17 levels in ERA SF correlate with disease activity and this may be due to increased production of MMP and cytokines by IL-17.     

Levels of soluble CD27 in sera and synovial fluid and its expression on memory T cells in patients with juvenile idiopathic arthritides

OBJECTIVE: CD27 is a member of tumour necrosis factor receptor family. Its expression is predominantly confined to mature lymphocytes and is strongly enhanced after cell activation. Shedding of the CD27 from the surface of activated cells is related to their effector phase. The aim of the present study was to evaluate the levels of soluble CD27 in sera and synovial fluids, together with its expression on circulating and synovial fluid (SF) memory T cells, in children with JIA. METHODS: Sera from 40 patients with active JIA were studied for soluble CD27. Paired SF samples were available in 20 patients. Sera from 12 age-matched patients affected with various acute infectious diseases and 12 age-matched healthy subjects were used as controls. In 8 JIA patients freshly isolated circulating and SF lymphocytes were stained for CD27 in CD4+CD45 RO+ T cell subpopulation and analyzed by cytometry. RESULTS: Soluble CD27 serum levels were significantly higher in patients with polyarticular JIA and acute systemic infectious diseases than in patients with active oligoarticular or healthy controls. Both polyarticular and oligoarticular JIA patients showed increased levels of soluble CD27 in SF when compared with paired serum samples (p = 0.01). In all the patients tested a significant enrichment of CD27- T cells was seen in the SF (median 39.5%, range 18-56%) when compared to paired CD4+CD45RO+ peripheral lymphocytes (median 19.5%, range 5-43%; p = 0.01). CONCLUSIONS: A clear enrichment of CD4+ memory SF T cells with a CD27-phenotype is observed when compared to correspondent circulating T lymphocytes. This issue is conceivably related to re-activation and recruitment of memory T cells to the site of inflammation, and to the subsequent expansion of a subpopulation of "effector" memory T cells.     

Neprilysin levels in plasma and synovial fluid of juvenile idiopathic arthritis patients

Objective Neprilysin (neutral endopeptidase, 3:4:24:11, CD10) (NEP) is a Zn metallopeptidase linked to controlling inflammation through the degradation of neuropeptides involved in neurogenic inflammation of chronic rheumatic diseases. The aim of our study was to evaluate circulating activity and cellular expression of NEP in the plasma of 58 children with juvenile idiopathic arthritis (JIA) and 52 controls. In 20 subjects requiring local steroid injection, NEP was measured in synovial fluid.Methods Plasma and synovial NEP were evaluated using a fluorimetric technique. Neprilysin, expressed as the antigen CD10, was determined on circulating and synovial fluid cells as mean fluorescence intensity (MFI) and as percentage of positive cells by two-color immunofluorescence.Results Circulating NEP levels were lower in JIA patients than in controls (42.0±16.6 vs 76.5±24 pmol/ml per min, P<0.001), while synovial fluid NEP values were higher than circulating levels (241.4±86.2 vs 40±15.3 pmol/ml per min, P<0.001). In monocytes, the percentage of CD10-positive circulating cells and the MFI in JIA were lower than in controls (11.6±5.2% vs 41.4±13%, P<0.001 and 18.1±7.5 vs 31.2±5.4, P<0.05, respectively). On synovial monocytes, the percentage of CD10-positive cells and the MFI were higher than on circulating monocytes (35.2±14.6% vs 9.1±2.4%, P<0.001 and 66.4±5.4 vs 22.8±14.7, P<0.001, respectively).Conclusions The downregulation of CD10 expression in monocytes and the reduction in NEP activity may be linked to the enzymes role in the control of peptides involved in the inflammation. The increased levels of NEP, MFI, and CD10-positive monocytes in synovial fluid, even though in plasma, might reflect a reactive effort to control synovial proliferation.     

Serum matrix metalloproteinases and tissue inhibitors of metalloproteinases in patients with early rheumatoid arthritis

OBJECTIVE: To analyze serum concentrations of matrix metalloproteinases (MMP) MMP-1, MMP-3, MMP-9, MMP-13, tissue inhibitors of MMP (TIMP) TIMP-1 and TIMP-2, and MMP/TIMP ratios in patients with early rheumatoid arthritis (RA) before and after 6 months of treatment with methotrexate (MTX). METHODS: The study group consisted of 30 patients with RA, not treated with disease modifying antirheumatic drugs or corticosteroids, with disease duration < 3 years. Twenty patients with osteoarthritis (OA) served as a control group. Analysis of serum concentrations of MMP and TIMP was based on a quantitative sandwich ELISA. RESULTS: Serum concentrations of MMP-1, MMP-3, MMP-9, and MMP-13 were higher in untreated patients with early RA than in OA patients (p < 0.001 in all cases). Serum levels of TIMP-1 and TIMP-2 dominated in the serum of RA patients compared with controls (p < 0.01 and p < 0.05, respectively). Ratios of MMP to TIMP were significantly higher in patients with early RA versus controls. Six months' treatment with MTX downregulated serum concentrations of MMP-1 (p < 0.001), MMP-3 (p < 0.001), MMP-9 (p < 0.001), MMP-13 (p < 0.01), and TIMP-1 (p < 0.05) in patients with RA. These changes were accompanied by significantly reduced ratios of MMP to TIMP. MTX treatment decreased markers of RA activity such as the number of painful and swollen joints, erythrocyte sedimentation rate, Disease Activity Score, and C-reactive protein. CONCLUSION: Patients with early RA are characterized by high serum concentrations of tissue-degrading metalloproteinases. Therapy with MTX resulted in clinical improvement and reduced serum MMP levels in patients with RA, confirming effectiveness of MTX in patients in early stages of the disease.     

Early joint erosions and serum levels of matrix metalloproteinase 1, matrix metalloproteinase 3, and tissue inhibitor of metalloproteinases 1 in rheumatoid arthritis

OBJECTIVE: To further evaluate the roles of matrix metalloproteinase 1 (MMP-1), MMP-3, and tissue inhibitor of metalloproteinases 1 (TIMP-1) in the pathogenesis of joint inflammation and articular erosions in early inflammatory arthritis. METHODS: Untreated patients with joint symptoms for <2 years were evaluated at presentation and followed up prospectively for 18 months. Swollen joint count and serum levels of C-reactive protein (CRP) were determined every 6 months. Serum levels of MMP-1, MMP-3, and TIMP-1 were measured by double-antibody sandwich enzyme-linked immunosorbent assay at the same time intervals. The number of joint erosions in serial radiographs of the hands and feet was also recorded. Analysis of synovial fluid levels of MMPs and TIMP-1 at presentation was completed in some patients. RESULTS: Of 175 patients evaluated at baseline, 85 had rheumatoid arthritis (RA), 39 had seronegative spondylarthropathy, 38 had undifferentiated arthritis, and 13 had self-limiting arthritis. Of 164 patients with available radiographs of the hands and feet at presentation, 33 (20.1%) had joint erosions. Baseline levels of MMP-1, MMP-3, and TIMP-1 were significantly higher (P = 0.0001, P = 0.013, and P = 0.0001, respectively) and ratios of TIMP-1:MMP-1 and TIMP-1:MMP-3 were significantly lower (P = 0.0001 and P = 0.013, respectively) in RA versus non-RA patients. In RA patients, serum levels of CRP correlated with MMP-3 and TIMP-1 levels, but not with MMP-1 levels. The number of erosions at presentation correlated with baseline levels of both MMP-1 and MMP-3, but not with levels of TIMP-1. One hundred one patients were followed up for the next 18 months. The number of patients with erosions and the number of erosions per patient increased significantly during this period. Area under the curve (AUC) measurements of MMP-1 and TIMP-1 levels, but not of MMP-3 levels, yielded significantly higher values in RA than in non-RA patients. In RA patients, only the AUC level of MMP-3 correlated with the AUC CRP level (r = 0.67, P = 0.0001), while only the AUC level of MMP-1 correlated with the number of new joint erosions (r = 0.28, P = 0.034). CONCLUSION: These data suggest an uncoupling of the pathophysiologic mechanisms associated with joint inflammation and articular erosion. Treatments that inhibit the production and activity of MMP-1 may preferentially limit the formation of new joint erosions and improve the long-term functional outcome of some patients with inflammatory arthritis.     

Regulation of peripheral blood and synovial fluid lymphocyte apoptosis in juvenile idiopathic arthritis

OBJECTIVE: Complex regulatory mechanisms are involved in the induction of apoptosis. Their impairment may play a role in the pathogenesis of several autoimmune diseases. Recently, we have described higher incidences of spontaneous apoptosis of peripheral blood (PB) lymphocytes in children with juvenile idiopathic arthritis (JIA). This study aimed to evaluate the regulatory mechanisms that may be responsible for this phenomenon. METHODS: Thirty-four JIA children were examined and compared with 20 healthy children of similar ages. Expression of regulatory proteins p53, Bax and Bcl-2 in lymphocytes isolated from PB and synovial fluid (SF) was assessed. Serum and SF levels of interleukin-15 (IL-15) were also evaluated. RESULTS: The study showed significantly decreased Bcl-2 expression in JIA PB lymphocytes, compared to both healthy control (p = 0.03) and JIA SF lymphocytes (p = 0.005). There were no significant differences found in Bax expression between groups or compartments examined. However, the Bax/Bcl-2 ratio was nearly two-fold higher in PB lymphocytes than in SF of JIA patients (p = 0.001). p53 expression in PB lymphocytes from both JIA and control children did not statistically differ. In JIA, however, p53 was significantly higher in PB than SF lymphocytes (p = 0.016). IL-15 levels were about 20-fold higher in JIA SF than in serum from either JIA or healthy children (p < 0.0001). CONCLUSION: The results suggest that a higher incidence of apoptosis of PB lymphocytes observed in JIA may be associated with down-regulation of Bcl-2, rather than with changes in expression of Bax and p53. In contrast, the low p53 expression and elevated IL-15 appear to provide mechanisms responsible for suppression of apoptosis in SF cells from JIA patients.     

Distinct expression pattern of IFN-alpha and TNF-alpha in juvenile idiopathic arthritis synovial tissue

OBJECTIVES: Recent laboratory and clinical data suggest that two prototype autoimmune diseases, systemic lupus erythematosus and rheumatoid arthritis are mainly driven by distinct cytokines, interferon (IFN)-alpha and tumour necrosis factor (TNF)-alpha, respectively. We here investigated the presence and characteristics of natural type I IFN-producing cells (IPCs), as well as IFN-alpha and TNF-alpha expression at sites of inflammation in juvenile idiopathic arthritis (JIA). METHODS: Peripheral blood (PB) and synovial fluid (SF) mononuclear cells (MNCs) (n = 25 each) from JIA patients with active disease were studied. IPCs were identified as BCDA-2(+)CD123(+)HLA-DR(+)CD45RA(+) cells, and dendritic cells (DCs) as CD11c(+)CD14(-/low)lin(-) cells by flow cytometry. IPCs and DCs were analysed for Toll-like receptor-7 and -9 mRNA expression by real-time polymerase chain reaction. IFN-alpha was measured by enzyme-linked immunosorbent assay in serum, SF and in supernatants of influenza virus-infected, cultured IPCs. Synovial tissues of n = 6 additional JIA patients were analysed by immunohistochemistry using mAbs against CD123, IFN-alpha, TNF-alpha, CD3, CD19 and CD138. RESULTS: IPCs were enriched in SF MNCs compared with PB MNCs in all JIA patients. Influenza-induced, but no spontaneous IFN-alpha release was detected from SF IPCs, and serum and SF IFN-alpha levels were not elevated. Nonetheless, in synovial tissue IFN-alpha producing cells accumulated at inflammatory lymph-follicular-like structures, while TNF-alpha producing cells were mostly found at the lining and sublining layers. CONCLUSIONS: These data suggest that besides TNF-alpha-expressing cells, IFN-alpha-producing IPCs are involved in initiation, maintenance or regulation of the inflammatory response in JIA.     

Serum matrix metalloproteinases and tissue inhibitors of metalloproteinases in different histological variants of rheumatoid synovitis.

OBJECTIVE: Rheumatoid synovitis is characterized by an invasive and tissue-destructive infiltrate of lymphocytes, macrophages and synoviocytes. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) produced by these cells are important in the remodelling of the articular tissues in rheumatoid arthritis (RA). The aim of this study was to explore whether the serum concentrations of MMPs and their inhibitors were correlated with the histological appearance of the disease. METHODS: Tissue and serum samples were obtained from 37 patients with clinically active RA and 30 with osteoarthritis (OA). Morphological analysis allowed the division of RA synovial specimens into two distinct types. In 22 samples only diffuse infiltrates of mononuclear cells without further microanatomical organization were found. In 15 specimens we observed lymphocytic conglomerates with germinal centre-like structures. Serum concentrations of interstitial collagenase (MMP-1), stromelysin-1 (MMP-3), gelatinase B (MMP-9), TIMP-1 and TIMP-2 were measured with an ELISA technique. RESULTS: Unique serum profiles of MMPs and TIMPs were identified in each of the two histological types of RA synovitis. The serum concentrations of MMP-1, MMP-3 and MMP-9 were higher in RA patients than in OA patients used as a control group (P<0.001 for all comparisons). These three MMPs dominated in the serum of RA patients with follicular synovitis compared with those with diffuse synovitis (P<0.05, P<0.01 and P<0.001 respectively). The analysis of the serum concentrations of TIMP-1 and TIMP-2 showed that their levels were also elevated in RA patients compared with OA patients (P<0.001 and P<0.01 respectively). Only TIMP-1 was found in a significantly higher concentration in the serum of RA patients with follicular synovitis than in those with diffuse synovitis (P<0.05). The serum concentrations of MMPs and TIMP-1 clearly identified patients with two different histological types of rheumatoid synovitis and with OA. Additionally, the analysis of clinical data showed that the rheumatoid disease in patients with follicular synovitis seemed to be more active than in those with diffuse synovitis. CONCLUSION: The morphological appearance of rheumatoid synovitis and the serum MMP and TIMP-1 profile were correlated with the clinical activity of the disease, confirming the heterogeneity of RA. These associations also suggest that patients with different histological forms of RA might require different treatment regimens.     

Levels of matrix metalloproteinase (MMP)-1 in paired sera and synovial fluids of juvenile idiopathic arthritis patients: relationship to inflammatory activity, MMP-3 and tissue inhibitor of metalloproteinases-1 in a longitudinal study

OBJECTIVES: To measure levels of the collagenases matrix metalloproteinase (MMP)-1 and -13 in the synovial fluid (SF) and serum of patients with juvenile idiopathic arthritis (JIA), and to correlate these measurements with inflammatory activity, levels of the collagenase activator MMP-3 and the tissue inhibitor of metalloproteinases-1 (TIMP-1). METHODS: Levels of MMP-1, -3, -13 and TIMP-1 were measured in paired SF and serum from 82 JIA patients using enzyme-linked immunsorbent assay and compared between subtypes and patients of different ages and disease durations. These levels were also correlated to the active joint count (AJC) and standard measures of inflammatory activity and therapeutic response, including erythrocyte sedimentation rate (ESR) and platelet count (PLT). RESULTS: MMP-1 was detected in JIA SF and correlated with PLT. MMP-3 levels were high in SF and detectable in serum where they correlated with PLT, ESR and AJC. MMP-13, however, was not detected in SF or serum. No differences were observed between patients grouped by subtype, age or disease duration. MMP-3 contributed the majority of total MMP in SF samples resulting in excess MMP levels over TIMP-1. CONCLUSIONS: MMP-1 is up-regulated in SF concordant with inflammatory activity in JIA. This was true for patients in all JIA subtypes and age groups, suggesting that the capability for degradation of type II collagen is present in early disease, and throughout the disease course. MMP-3 may be important in the activation of collagenases and the saturation of exogenous inhibitors. Serum MMP-3 may therefore be a useful, measurable and specific marker of active disease in JIA.     

Relationships between matrix metalloproteinases and tissue inhibitor of metalloproteinases in the wall of abdominal aortic aneurysms.

AIM: The pathologic feature of aortic aneurysm is considered to be the remodeling of the aortic wall, involving fragmentation and decrease of elastic fibers in the tunica media. Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, have been implicated in collagen and elastin degeneration within the aortic wall. The precise relationship among MMPs and tissue inhibitor of metalloproteinases (TIMPs) is still unclear. We have studied the expression of MMP-2, MMP-9 tissue inhibitor of metalloprotein-1 (TIMP-1), TIMP-2 and membrane type 1-MMP (MT-1-MMP) in the wall of small AAAs (30-45 mm), large AAAs (>45 mm) and controls (<25 mm). We investigated the relationship among expressions of MMP-2, TIMP-2 and MT1-MMP in the walls. METHODS: The aortic walls in the patients with AAA were harvested from the maximum diameter, while the aortic walls in autopsy cases were harvested as controls. We analyzed tissue distribution of cell types by immunochemistry, protein expression by Western blotting and mRNA expression by competitive polymerase chain reaction. RESULTS: They consisted of 11 in controls, 8 in small AAAs and 26 in large AAAs. Among the MMPs-positive-cells, mainly macrophage, MMP-2-positive cells were in the intima, but MMP-9-positive cells in the intima and adventitia. In the small size, MMP-2 and MMP-9 mRNA were higher than those of control. In the large size, MT1-MMP and MMP-9 mRNA were higher than those of the controls. In the mRNA level of the whole AAA, significant correlations were present between MMP-2 and MMP-9, between MMP-2 and TIMP-1, and between MMP-9 and TIMP-1. These expressions were confirmed by Western blotting. CONCLUSION: We concluded as follows: 1) MMP-2 and MMP-9 may play an important role in the developmental process of AAA. 2) TIMP-1 plays an important role of interacting MMP-2 and/or MMP-9. 3) MMP-2 and MT1-MMP may play an important role in the early stages of AAAs.     

Serum levels of tissue inhibitor of metalloproteinases in patients with mixed connective tissue disease

OBJECTIVE: To determine serum tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 levels in patients with mixed connective tissue disease (MCTD) and investigate whether these levels were correlated with the clinical or serological features of this disease. METHODS: Serum TIMP-1 and TIMP-2 levels were measured with specific enzyme-linked immunosorbent assays. Serum samples from 26 patients with MCTD and 18 healthy individuals were examined. RESULTS; Serum levels of TIMP-1 were significantly higher in patients with MCTD than those in healthy individuals (mean +/- SD: 218.9 +/- 50.8 ng/ml versus 160.0 +/- 38.7 ng/ml, P < 0.0001). MCTD patients with elevated TIMP-1 had esophageal involvement at a significantly higher incidence than those without (77.8% versus 35.3%, p < 0.05). There was no difference in serum TIMP-2 levels between patients with MCTD and healthy controls (75.6 - 11.9 ng/ml versus 77.3 +/- 10.7 ng/ml). CONCLUSION: These results suggest that TIMP-1 is involved in the pathogenesis of MCTD, and that TIMP-1 may be a serological marker for the presence of esophageal involvement in these patients.     

Elevated concentrations of monocyte derived cytokines in synovial fluid of children with enthesitis related arthritis and polyarticular types of juvenile idiopathic arthritis

OBJECTIVE: Cytokines are the major mediators of joint damage in chronic arthritis. Data on synovial fluid (SF) cytokine concentrations in patients with juvenile idiopathic arthritis (JIA), especially enthesitis related arthritis (ERA), are limited. We measured levels of different monocyte derived cytokines, T cell derived cytokines, and a proinflammatory chemokine in SF specimens from children with ERA or polyarticular (Poly) rheumatoid factor (RF)-negative JIA. METHODS: Macrophage products [tumor necrosis factor-a (TNF-a), interleukin 1ss (IL-1ss), IL-6, IL-12p40)], T lymphocyte products [IL-2, IL-4, interferon-g (IFN-g)], and a proinflammatory chemokine (IL-8) were assayed using ELISA in SF specimens from 53 patients with JIA [ERA 34, polyarticular RF-negative 19] and 40 patients with rheumatoid arthritis (RA). RESULTS: In the ERA group, median SF cytokine levels were higher compared to RA (all values are pg/ml): IL-1ss [< 15.6 (< 15.6-213) vs < 15.6 (< 15.6-41); p < 0.01], IL-12p40 [236 (< 15.6-1714) vs 21 (< 15.6-520); p < 0.0001], and IL-6 [1139 (< 4.6-2187) vs 835 (< 4.6-875); p < 0.0001]. TNF-a and IFN-g levels were similar to RA. IL-8 levels were significantly less than RA (p < 0.0001). The median levels of IL-1ss [39.4 (< 15.6-558) vs < 15.6 (< 15.6-41); p < 0.0001] and IL-12p40 [209 (< 15.6-849) vs 21 (< 15.6-520); p < 0.0001] were higher in patients with Poly-JIA compared to RA. TNF-a, IL-6, and IL-8 levels in Poly-JIA were comparable to RA. IL-2 and IL-4 were not detectable in any patient with JIA. Cytokine profile comparison between the 2 subsets revealed that the median IL-6 [1139 (< 4.6-2187) vs 790 (17.4-2119); p < 0.01] and IFN-g levels [235 (< 4.6-600) vs < 4.6 (< 4.6-412); p < 0.0001] were higher in ERA than in Poly-JIA. In contrast, median IL-8 levels were higher in Poly-JIA [200 (3.8-200)] compared to ERA [74.6 (4-200); p < 0.001]. However, there was no difference in levels of TNF-a, IL-1ss, and IL-12p40 between patients with these 2 subtypes of JIA. CONCLUSION: SF levels of IL-1ss and IL-12p40 are increased in both Poly-JIA and ERA as compared to RA. IL-6 levels were higher in ERA compared to RA. Levels of TNF-a were comparable to RA in both Poly-JIA and ERA. This suggests that joint inflammation in JIA is mediated predominantly by monocytes. In ERA the levels of IL-6 and IFN-g are higher than in Poly-JIA. The increase in IFN-g in children with ERA with undetectable IL-4 suggests a Th1-dominant immune response in this disease subset.