Scintigraphic evaluation of synovial inflammation in rheumatoid arthritis with 99mtechnetium-labelled human polyclonal immunoglobulin G

The aim of this study was to investigate whether ^99mtechnetium-labelled polyclonal human immunoglobulin G (^99mTc-IgG) scintigraphy reflects synovial inflammation in patients with rheumatoid arthritis (RA). We evaluated 29 patients with RA for this reason and found a highly significant correlation between total scintigraphic scores and total tenderness scores (r=0.781, P < 0.001). A significant correlation was also found between ^99mTc-IgG scintigraphic scores and tenderness in all joints other than the shoulders. The ^99mTc-IgG scintigraphy had a sensitivity of 69% and specificity of 88% in cases with tenderness and 72% and 81%, respectively, in cases with swelling. Total scintigraphic scores were correlated with serum levels of C-reactive protein (r=0.401, P < 0.05) but not with erythrocyte sedimentation rate (r=0.149, P > 0.05). The correlation between disease activity scores and total scintigraphic scores was also found to be significant (r=0.812, P < 0.001). We suggest that ^99mTc-IgG scintigraphy is a reliable and objective method in detecting synovial activity and can be appropriate for observing disease prognosis in clinical trials with RA. Received: 16 June 2000 / Accepted: 27 August 2000     

Studies of serum immunoglobulin binding to synovial fibroblast cell cultures from patients with rheumatoid arthritis

Using a sensitive 125I-protein A (PrA) binding assay to detect cell surface IgG, we have studied seven different synovial fibroblast cell cultures from patients with rheumatoid arthritis (RA). When these cultures were incubated in the presence of serum from 18 autologous and allogeneic RA patients (all seropositive), we were unable to detect significant IgG binding. Since IgM rheumatoid factor (RF) can block PrA binding, sera were absorbed with aggregated IgG to remove RF without affecting the results. Similar studies on three cell lines with seven rheumatoid sera were performed by antibody-dependent cell-mediated cytotoxicity. No significant cytotoxicity was observed. Since antibodies to collagen are present in rheumatoid sera, several cultures were incubated with ascorbic acid (12.5 microgram/ml) to optimize synthesis of cell surface collagen. These culture conditions did not affect serum immunoglobulin binding by the 125I-PrA assay. Thus, we can find no evidence for a direct humoral immune mediation of synovial proliferation in rheumatoid arthritis. These data do not support the hypothesis that the inflammatory process within the synovium of RA patients is an immunologic response to a fibroblast-associated antigen in the synovial membrane.     

Comparative specificities of serum and synovial cell 19S IgM rheumatoid factors in rheumatoid arthritis

Rheumatoid factor (RF) may play a role in sustaining the inflammatory events and tissue damage in rheumatoid arthritis (RA). However, many serum RF have greater specificity for rabbit IgG than for human IgG, thus raising questions about RF pathogenicity in RA. Serum RF also has specificity for human IgG subclasses 1, 2 and 4, but not for IgG3. The synovium is central to the pathology of RA; thus, RF made there may have greater pathogenicity than serum RF. We examined the specificity of 19S IgM RF in an RF plaque forming cell assay (RF-PFC) using RA synovial cells (RSC). We found that: (1) RSC produced greater numbers of RF-PFC/10(6) cells than did RA peripheral blood mononuclear cells (PBM); (2) RSC RF-PFC had greater specificity for human than for rabbit IgG compared to autologous serum RF; (3) RSC RF had significantly greater specificity for human IgG3 relative to autologous serum RF. In contrast, RSC RF and autologous serum RF had the same relative specificities for polyclonal human IgG, IgG1, IgG2, and IgG4. Thus, the specificity of much of the RF synthesized by RSC differed from serum RF. The potential pathogenic significance of these observations is discussed.     

Resistin in rheumatoid arthritis synovial tissue, synovial fluid and serum

BACKGROUND: Resistin is a newly identified adipocytokine which has demonstrated links between obesity and insulin resistance in rodents. In humans, proinflammatory properties of resistin are superior to its insulin resistance-inducing effects. OBJECTIVES: To assess resistin expression in synovial tissues, serum and synovial fluid from patients with rheumatoid arthritis, osteoarthritis and spondylarthropathies (SpA), and to study its relationship with inflammatory status and rheumatoid arthritis disease activity. METHODS: Resistin expression and localisation in synovial tissue was determined by immunohistochemistry and confocal microscopy. Serum and synovial fluid resistin, leptin, interleukin (IL)1beta, IL6, IL8, tumour necrosis factor alpha, and monocyte chemoattractant protein-1 levels were measured. The clinical activity of patients with rheumatoid arthritis was assessed according to the 28 joint count Disease Activity Score (DAS28). RESULTS: Resistin was detected in the synovium in both rheumatoid arthritis and osteoarthritis. Staining in the sublining layer was more intensive in patients with rheumatoid arthritis compared with those with osteoarthritis. In rheumatoid arthritis, macrophages (CD68), B lymphocytes (CD20) and plasma cells (CD138) but not T lymphocytes (CD3) showed colocalisation with resistin. Synovial fluid resistin was higher in patients with rheumatoid arthritis than in those with SpA or osteoarthritis (both p<0.001). In patients with rheumatoid arthritis and SpA, serum resistin levels were higher than those with osteoarthritis (p<0.01). Increased serum resistin in patients with rheumatoid arthritis correlated with both CRP (r=0.53, p<0.02), and DAS28 (r=0.44, p<0.05), but not with selected (adipo) cytokines. CONCLUSION: The upregulated resistin at local sites of inflammation and the link between serum resistin, inflammation and disease activity suggest a role for resistin in the pathogenesis of rheumatoid arthritis.     

Glycolytic activity in human synovial lining cells in rheumatoid arthritis.

It was conceivable that the previously reported elevated pentose-shunt activity in human rheumatoid synoviocytes could be at the expense of glycolytic activity. To test this possibility the activities of glyceraldehyde 3-phosphate and lactate dehydrogenase, the two dehydrogenase enzymes of the latter pathway, have been investigated in the synovial lining cells in fresh sections of nonrheumatoid and rheumatoid synovial tissue. To measure the activity solely in the lining cells, apart from that in underlying infiltrating cells, quantitative cytochemical reactions have been used; the activities were measured by microdensitometry. The results showed highly and significantly increased activity of both enzymes in the rheumatoid cells. Increased activity was also found in synoviocytes in nonrheumatoid synovial tissue after trauma, so that the increased activity of these enzymes is not characteristic of the rheumatoid condition. However, the results indicate that the increased pentose shunt activity in rheumatoid synovial lining cells is not at the expense of glycolytic activity but may be part of an enhanced potential for utilising glucose 6-phosphate in these cells.     

Binding of normal human mononuclear cells to blood vessels in rheumatoid arthritis synovial membrane

We examined the binding of mononuclear cells to blood vessels in the rheumatoid arthritis synovial membrane. Two of 4 synovia that had lymphocyte-rich areas contained blood vessels adhesive for mononuclear cells. These reactive vessels showed striking similarities to high endothelial venules of the paracortical region of lymph node, where normal lymphocyte-endothelial cell adhesion and lymphocyte emigration into tissue occurs.     

Quantitation of human synovial mast cells in rheumatoid arthritis and other rheumatic diseases

We examined sections of synovial membranes from 14 patients with rheumatoid arthritis (RA), 7 with other rheumatic diseases, and 10 with no apparent joint disease. Patients with RA and other rheumatic diseases had significantly more synovial mast cells/vessel than patients with no joint disease (0.49 and 0.20, respectively, versus 0.03). They also had significantly more total mast cells/10 fields than patients with no joint disease (9.9 and 5.0, respectively, versus 0.4). Within the rheumatoid group, patients with active disease had more total mast cells/10 fields than patients clinically considered to have end-stage disease (P < 0.05). Synovial basophils were not identified in any patient. Synovial vascularity was similar for all groups (2.3 vessels/field). The role of the synovial mast cell in RA and other rheumatic diseases remains to be determined.     

Phenotypic characterization of 3H-thymidine incorporating cells in rheumatoid arthritis synovial membrane

Summary Tritiated-thymidine incorporating cells in synovial tissue samples from ten patients with definite or classic rheumatoid arthritis (RA) were studied by combining two techniques. Tritiated-thymidine-labelled cells were seen in autoradiography and simultaneously the subtype of them was determined with immunoperoxidase staining using monoclonal antibodies. Tritiated-thymidine-labelled cells comprised 0.8±0.4% of all the inflammatory cells in RA synovial membrane. Of all ³H-thymidine-labelled cells 34±17% were positive for OKT8 and 19±8% for OKT4 monoclonal antibodies. OKM1-positive cells comprised 7±3% of all ³H-thymidine labelled cells, whereas only a few (3±4%) of them were positive for pan-B monoclonal antibody. This study emphasizes the importance of activated OKT8 lymphocytes in RA synovial membrane.     

Mononuclear cells in human synovial fluid. Identification of lymphoblasts in rheumatoid arthritis

A simple method was developed to identify large mononuclear (LMN) cells in human synovial fluid based on morphology and staining with Sudan black B. All cells were classified as monocyte-derived macrophages (MDM), lymphoblasts (LB), or synovial lining cells (SLC). Lymphoblasts were seen in 58 of 60 rheumatoid fluids (mean: 69 ± 18% LB per LMN cells). However lymphoblasts were rarely seen in synovial fluids from patients with crystal-induced synovitis or bacterial infections.     

Predominance of IgG1 and IgG3 subclasses of autoantibodies to peptidylarginine deiminase 4 in rheumatoid arthritis

Analysis of IgG subclass distribution of antibodies may provide insights into the mechanisms driving antibody production. Here, we have first determined IgG subclass distribution of anti-recombinant peptidylarginine deiminase 4 (anti-hPADI4) antibodies in sera from patients with rheumatoid arthritis (RA). Sera from 103 RA patients were screened to IgG anti-PADI4 using recombinant antigens. For positive samples, the subclass distribution of IgG anti-hPADI4 was determined by means of establishing the equipotency of four HRP-labeled IgG subclass-specific monoclonal antibodies. The subclass profiles were compared among individuals with different disease status. Thirty-three out of 103 RA patients were determined as IgG anti-hPADI4-positive. As expressed by percentage levels to total IgG anti-hPADI4 activity, IgG1 and IgG3 were determined to be the predominant subclasses of anti-hPADI4. Furthermore, distinct subclass distribution patterns were observed in patients with different disease status. The IgG subclass distribution of anti-hPADI4 indicates that a leading T lymphocyte-regulated IgG1 and IgG3 responses may contribute to a better understanding of the role of anti-PADI4 in RA.     

Diminished clearance of soluble aggregates of human immunoglobulin G in patients with rheumatoid arthritis

Investigation of the capacity of the mononuclear phagocyte system to remove immune complexes from the circulation was performed by the administration of 125I-labelled aggregates of human immunoglobulin G (AIgG) to patients with seropositive rheumatoid arthritis and healthy volunteers. It was found that the rate at which AIgG disappeared from the circulation was significantly prolonged in patients with RA, t1/2 61 +/- 49 min, versus 26 +/- 8 min in healthy volunteers (p less than 0.01). We were not able to establish a correlation between the t1/2 of AIgG and immune complex levels in the circulation, or between t1/2 and articular disease activity (Ritchie index). The sites of removal of AIgG from the circulation were analysed by determining radioactivity levels detectable over liver, spleen and heart. No correlation was found between t1/2 and liver/spleen uptake ratios. We have demonstrated that the removal of AIgG from the circulation of patients with RA is abnormal, though the biological significance of this finding remains to be determined.     

Dickkopf-1 perpetuated synovial fibroblast activation and synovial angiogenesis in rheumatoid arthritis

Clinical Rheumatology - Dickkopf-1 (Dkk-1), a regulatory molecule of the Wnt pathway, is elevated and leads to bone resorption in patients with RA. This study is aimed to investigate the...     

Synovial vascular patterns and angiogenic factors expression in synovial tissue and serum of patients with rheumatoid arthritis

OBJECTIVE: To determine whether subgroups of rheumatoid arthritis (RA) patients classified according to their synovial vascular pattern have a different expression of angiogenic mediators or exhibit distinct clinical or biological characteristics. METHODS: Arthroscopies were performed in 27 patients with RA and synovial samples were obtained. Vascular morphology was classified in three patterns: straight (S), tortuous (T) and mixed (M). Immunostaining was performed with anti-vascular endothelial growth factor (anti-VEGF), anti-vascular endothelial growth factor receptor (VEGFR)-1, anti-VEGFR-2, anti-IL-8 and anti-TGF-beta, and measured by digital image analysis. Serum levels of VEGF, TGF-beta and IL-8, and clinical, radiographic and serological data were also analysed. RESULTS: Eleven (41%) patients had the S pattern, nine (33%) the M pattern and seven (26%) the T pattern. The S and M groups had a higher prevalence of rheumatoid factor positivity and erosive disease, and higher levels of markers of systemic inflammation compared with the T group. Synovial expression of VEGF was higher in the S and T groups compared with the M group, whereas TGF-beta was higher in the T compared with the S and M groups. Distinct synovial distribution of VEGF and TGF-beta between groups was also observed. CONCLUSIONS: This preliminary study suggests that RA patients with the S and M patterns share different clinical, biological and serological characteristics compared with those with the T pattern, which may constitute a group with less severe disease. Differences in the intensity and distribution of synovial expression of VEGF and TGF-beta observed between groups could have pathophysiological relevance. However, larger, prospective multicentre studies would be need to determine the clinical relevance of vascular patterns in RA.