Objective. Interleukin-17 (IL-17) is a proinflammatory cytokine that is expressed in the synovium of rheumatoid arthritis (RA) patients. This T cell cytokine is implicated in the initiation phase of arthritis. However, the role of IL-17 during the effector phase of arthritis has still not been identified; this was the objective of the present study.Methods. Mice with collagen-induced arthritis (CIA) were treated with polyclonal rabbit anti-murine IL-17 (anti-IL-17) antibody-positive serum or normal rabbit serum after the first signs of arthritis. In addition, during a later stage of CIA mice were selected and treated with anti-IL-17 antibody or control serum. Arthritis was monitored visually, and joint pathology was examined radiologically and histologically. Systemic IL-6 levels were measured by enzyme-linked immunosorbent assay, and local synovial IL-1 and receptor activator of NF-B ligand (RANKL) expression was analyzed using specific immunohistochemistry.Results

IL-32 is a recently discovered cytokine that induces TNF␣, IL-1␤, IL-6, and chemokines. We investigated whether IL-32 is expressed in the synovia of patients with rheumatoid arthritis (RA) and studied associations with disease severity and the presence of other cytokines. Immunohistochemistry revealed that IL-32 is highly expressed in RA synovial tissue biopsies, whereas IL-32 was not observed in synovial tissues from patients with osteoarthritis. Moreover, in synovial biopsies from 29 RA patients with active disease, the level of IL-32 staining correlated with erythrocyte sedimentation rate, a marker of systemic inflammation (R ‫؍‬ 0.63 and P < 0.0003). Synovial staining of IL-32 also correlated with indices of synovial inflammation (R ‫؍‬ 0.80 and P < 0.0001) as well as synovial presence of TNF␣ (R ‫؍‬ 0.68 and P < 0.004), IL-1␤ (R ‫؍‬ 0.79 and P < 0.0001), and IL-18 (R ‫؍‬ 0.82 and P < 0.001). IL-32 was a potent inducer of prostaglandin E2 release in mouse macrophages and human blood monocytes, an important property for inflammation. After the injection of human IL-32␥ into the knee joints of naïve mice, joint swelling, with pronounced influx of inflammatory cells and cartilage damage, was observed. In TNF␣-deficient mice, IL-32-driven joint swelling was absent and cell influx was markedly reduced, but loss of proteoglycan was unaffected, suggesting that IL-32 activity is, in part, TNF␣-dependent. IL-32, strongly associated with TNF␣, IL-1␤, and IL-18, appears to play a role in human RA and may be a novel target in autoimmune diseases.autoimmune ͉ inflammation ͉ tumor necrosis factor

Objective. To study the expression of Toll-like receptor 2 (TLR-2) and TLR-4 and its association with proinflammatory cytokines in synovial tissue from patients with rheumatoid arthritis (RA), osteoarthritis (OA), and healthy individuals.Methods. Synovial tissue specimens from 29 RA patients were stained for TLR-2, TLR-4, and proinflammatory cytokines (interleukin-1␤ [IL-1␤], IL-12, IL-17, IL-18, and tumor necrosis factor ␣ [TNF␣]). The expression of TLR-2, TLR-4, and cytokines as well as the degree of inflammation in synovial tissue were compared between patients with RA, patients with OA (n ‫؍‬ 5), and healthy individuals (n ‫؍‬ 3). Peripheral blood mononuclear cells (PBMCs) were incubated with IL-12 and IL-18, and TLR expression was assessed using fluorescence-activated cell sorter analysis. Production of TNF␣ and IL-6 was measured using Luminex bead array technology.Results. In RA synovial tissue, the expression of TLR-2 was slightly higher than that of TLR-4. Interestingly, both TLR-2 and TLR-4 were expressed at higher levels in moderately inflamed synovium, as compared with synovial tissue with no or severe inflammation.

IL-17 is a T cell-derived proinflammatory cytokine in experimental arthritis and is a stimulator of osteoclastogenesis in vitro. In this study, we report the effects of IL-17 overexpression (AdIL-17) in the knee joint of type II collagen-immunized mice on bone erosion and synovial receptor activator of NF-κB ligand (RANKL)/receptor activator of NF-κB/osteoprotegerin (OPG) expression. Local IL-17 promoted osteoclastic bone destruction, which was accompanied with marked tartrate-resistant acid phosphatase activity at sites of bone erosion in cortical, subchondral, and trabecular bone. Accelerated expression of RANKL and its receptor, receptor activator of NF-κB, was found in the synovial infiltrate and at sites of focal bone erosion, using specific immunohistochemistry. Interestingly, AdIL-17 not only enhanced RANKL expression but also strongly up-regulated the RANKL/OPG ratio in the synovium. Comparison of arthritic mice from the AdIL-17 collagen-induced arthritis group with full-blown collagen-arthritic mice having similar clinical scores for joint inflammation revealed lower RANKL/OPG ratio and tartrate-resistant acid phosphatase activity in the latter group. Interestingly, systemic OPG treatment prevented joint damage induced by local AdIL-17 gene transfer in type II collagen-immunized mice. These findings suggest T cell IL-17 to be an important inducer of RANKL expression leading to loss of the RANKL/OPG balance, stimulating osteoclastogenesis and bone erosion in arthritis.

Rheumatoid arthritis is characterized by an intermittent course of disease with alternate periods of remission and relapse. T cells, and in particular the T-cell cytokine interleukin-17 (IL-17), are expected to be involved in arthritic flares. Here, we report that neutralizing endogenous IL-17 during reactivation of antigen-induced arthritis prevents joint inflammation and bone erosion. Synovial IL-17 mRNA expression was clearly up-regulated during primary arthritis and was further enhanced after antigen rechallenge. Neutralization of IL-17 significantly prevented joint swelling at day 1 of flare and significantly suppressed joint inflammation and cartilage proteoglycan depletion at day 4, as assessed by histology. Blocking IL-17 also clearly reduced bone erosions. Cathepsin K, a marker of osteoclast-like activity, and synovial RANKL mRNA expression were both suppressed. The degree of bone erosions strongly correlated with the severity of joint inflammation, suggesting that anti-IL-17 treatment reduced bone erosion by suppressing joint inflammation. Interestingly, blocking IL-17 suppressed synovial expression of both IL-1␤ and tumor necrosis factor-␣, whereas blocking IL-1 did not affect tumor necrosis factor-␣ levels. These data indicate that IL-17 is an important upstream mediator in joint pathology Rheumatoid arthritis (RA) is a systemic joint disease characterized by progressive destructive joint inflammation. Although RA is considered an autoimmune disease, the autoantigen(s) is still not identified. Interestingly, CTLA4Ig treatment in patients with RA showed promising improvement of the ACR50 and ACR70 responses. 1 This treatment blocks the interaction of CD80/86 on antigen-presenting cells with CD28 on naïve T cells. This interaction is required for optimal T-cell activation. This study supports the theory that (CD4 ϩ ) T cells play a key role in the pathogenesis of RA. [2][3][4] The contribution of T cells in the joints can be related to antigen-dependent and -independent mechanisms, such as direct cell contact, which can induce cytokine and protease production by macrophages and fibroblasts. 5 Furthermore, RA is characterized by an intermittent course of the disease with alternate periods of remission and relapse. The cause of a flare-up reaction during RA is unclear, and both antigen-specific and antigen-nonspecific T cells may play a role. 4 Studies in animal models for experimental arthritis have resulted in better understanding of the role of different cell types and various cytokines during arthritic flares. In antigen-induced arthritis, the capacity to develop arthritis can be transferred by lymphocytes, 6 in particular by cell fractions enriched for T cells, and high

Objective. To examine the role of interleukin-17 receptor (IL-17R) signaling in cartilage destruction and its interrelationship with synovial IL-1 expression during chronic reactivated streptococcal cell wall (SCW)-induced arthritis. Methods. SCW arthritis was repeatedly induced in wild-type (WT) and IL-17R-deficient (IL-17R-/-) mice. At different time points, joint inflammation was assessed by using calipers to measure joint swelling. On day 42, mice were killed, and knee joints were removed for histologic analysis. Quantitative polymerase chain reaction (PCR) analyses for different proinflammatory mediators and matrix metalloproteinases (MMPs) were performed on inflamed synovium from WT and IL-17R -/-mice after 5 repeated injections of SCW fragments. Results. IL-17R

The proinflammatory T cell cytokine IL-17 is a potent inducer of other cytokines such as IL-1 and TNF-α. The contribution of TNF in IL-17-induced joint inflammation is unclear. In this work we demonstrate using TNF-α-deficient mice that TNF-α is required in IL-17-induced joint pathology under naive conditions in vivo. However, overexpression of IL-17 aggravated K/B×N serum transfer arthritis to a similar degree in TNF-α-deficient mice and their wild-type counterparts, indicating that the TNF dependency of IL-17-induced pathology is lost under arthritic conditions. Also, during the course of the streptococcal cell wall-induced arthritis model, IL-17 was able to enhance inflammation and cartilage damage in the absence of TNF. Additional blocking of IL-1 during IL-17-enhanced streptococcal cell wall-induced arthritis did not reduce joint pathology in TNF-deficient mice, indicating that IL-1 is not responsible for this loss of TNF dependency. These data provide further understanding of the cytokine interplay during inflammation and demonstrate that, despite a strong TNF dependency under naive conditions, IL-17 acts independently of TNF under arthritic conditions.

The dystrophin-glycoprotein complex, which comprises ␣-and ␤-dystroglycan, sarcoglycans, and utrophin/dystrophin, links the cytoskeleton to agrin and laminin in the basal lamina in muscle and epithelial cells. Recently, agrin was identified as a major heparan sulfate proteoglycan in the glomerular basement membrane. In the present study, we found mRNA expression for agrin, dystroglycan, and utrophin in kidney cortex, isolated glomeruli, and cultured podocytes and mesangial cells. In immunofluorescence, agrin was found in the glomerular basement membrane. The antibodies against ␣-and ␤-dystroglycan and utrophin revealed a granular podocyte-like staining pattern along the glomerular capillary wall. With immunoelectron microscopy, agrin was found in the glomerular basement membrane, dystroglycan was diffusely found over the entire cell surface of the podocytes, and utrophin was localized in the cytoplasm of the podocyte foot processes. In adriamycin nephropathy, a decrease in the glomerular capillary wall staining for dystroglycan was observed probably secondary to the extensive fusion of foot processes. Immunoelectron microscopy showed a different distribution pattern as compared to the normal kidney, with segmentally enhanced expression of dystroglycan at the basal side of the extensively fused podocyte foot processes. In passive Heymann nephritis we observed no changes in the staining intensity and distribution of the dystrophin-glycoprotein complex by immunofluorescence and immunoelectron microscopy. From these data, we conclude that agrin, dystroglycan, and utrophin are present in the glomerular capillary wall and their ultrastructural localization supports the concept that these molecules are involved in linking the podocyte cytoskeleton to the glomerular basement membrane. (Am J Pathol 2000, 156:1749 -1765) Dystroglycan (DG) is an important member of the dystrophin-glycoprotein complex (DGC) which links the subsarcolemmal cytoskeleton to the basal lamina in skeletal muscle.1 The importance of this link becomes clear from the severe muscular dystrophies resulting from mutations in genes that encode different members of the DGC. 2-5