Dendritic cells in the pathogenesis of rheumatoid arthritis

Summary The cause of rheumatoid arthritis is unknown. It appears that abnormal or overstimulated cell-mediated immune mechanisms are operating. Dendritic cells, with their potent antigen presenting and immunostimulatory properties, have been found in increased numbers of rheumatoid synovial fluids and membranes. It is postulated that these cells play a key role in inducing and perpetuating the immune response with subsequent synovial proliferation and joint destruction.     

Cytokine production by synovial T cells in rheumatoid arthritis.

OBJECTIVE: To investigate the production of cytokines by T cells in patients with rheumatoid arthritis (RA), reactive arthritis (REA) and osteoarthritis (OA). METHODS: The lymphokines interleukin (IL)-2, IL-4, interferon gamma (IFN-gamma) and tumour necrosis factor beta (TNF-beta), as well as the monokines IL-1, IL-6 and TNF-alpha, were measured by immunoassays in sera and synovial fluid (SF) from patients with RA, REA and OA. In addition, cytokine expression was studied by immunohistochemistry in synovial membrane tissue sections from patients with RA and OA. RESULTS: Almost 60% of RA sera contained at least one of the cytokines investigated, though in low concentrations, whereas cytokines were generally not detectable in sera from REA and OA patients. In contrast, cytokines were found in virtually all SF; thus, the majority of SF from RA patients contained IFN-gamma (median level 17 pg/ml) in addition to the monokines IL-6 (4700 pg/ml) and TNF-alpha (157 pg/ml). IFN-gamma and IL-6 (but not TNF-alpha) were also frequently measured in SF from REA patients, whereas OA samples typically contained only IL-6. Immunohistochemical analysis of tissue sections from RA patients revealed lymphokine expression in 0.1-0.3% of T cells, particularly IL-2 and IFN-gamma, and to a lesser extent also IL-4. Interestingly, the expression of TNF-alpha and IL-6 by synovial T cells was also observed. The majority of cytokine-expressing T cells were CD4-positive T-helper cells typically found in perivascular areas, whereas cytokine-producing CD8-positive T cells were found distributed throughout the synovium. As expected, in specimens from OA patients, T cells were much less abundant and expression of cytokines could not be detected. CONCLUSION: These data clearly demonstrate production of cytokines by T cells in RA synovial tissue, indicating that activated T cells play a role in the pathophysiological events of RA.     

Contribution of inherited factors to rheumatoid arthritis.

A total of 231 sibships of the same sex (186 female, 45 male), in which the proband had classical or definite rheumatoid arthritis (RA) have been selected from rheumatology clinics. Each sibship member was questioned about symptomatic joints, which were then examined. Hospital records, radiographs, and rheumatoid factor measurements allowed each sibling to be classified as having classical, definite, probable, or no RA. Each sibling was typed for HLA-A and B and was classified as sharing two, one, or zero HLA haplotypes with the proband. Concordance rates for classical and definite RA were three times greater in sibships of women than of men (9.3 v 3.0%). Concordance rates in HLA identical sibships were twice those in hemi- and non-identical sibships (15.5, 7.1, and 5.2%, respectively). Probable RA was more common in male and HLA hemi- and non-identical sibships. These results suggest that female sex and the two inherited HLA haplotypes are important for the presence and expression of RA. Although environmental factors may be shared more in twins than siblings, a concordance rate of 20.5% in seropositive HLA identical sibships of the same sex compared with 30% in monozygotic twins suggests that sex and HLA type account for about two thirds of the inherited risk of RA.     

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.     

Altered expression of TPP1 in fibroblast-like synovial cells might be involved in the pathogenesis of rheumatoid arthritis

We undertook this study to determine whether the altered expression of telomeric proteins TPP1 and POT1 in fibroblast-like synovial cells (FLS) could provide insights into the pathogenesis of rheumatoid arthritis (RA). FLS were isolated from patients with RA, osteoarthritis (OA) and traumatic joint disease, and cultured in vitro. TPP1 and POT1 mRNA level of FLS were measured using real-time quantitative polymerase chain reaction (RT-qPCR) in 42 RA, 23 OA and 13 healthy cases. Immunofluorescence staining and Western blot were used to detect the expression of TPP1 and POT1 protein. Expression of TPP1 and POT1 mRNA was significantly reduced in RA cases (P < 0.001, respectively), and no significant difference was observed between OA and healthy cases (P > 0.05, respectively). Confocal microscopy images showed TPP1 and POT1 proteins mainly located in nucleus of FLS. Western blot demonstrated that TPP1 protein level was significantly reduced in RA cases (P < 0.001), and POT1 protein expression was not statistical significance among RA, OA patients and healthy cases (P > 0.05). Significant negative correlation was observed between level of TPP1 mRNA and titers of anti-CCP antibody (P < 0.001), RF (P < 0.01). Altered expression of TPP1 might contribute to persistent proliferation of FLS in RA, further study on functions of telomeric proteins in RA would be needed.     

Cellular immunity to possible synovial antigens in rheumatoid arthritis.

A reaction has been demonstrated between extracts of synovial cells removed from intact rheumatoid knee joints and autologous leucocytes. The cell mediated immunity test system used was leucocyte migration inhibition. Variable reactions were found with a spectrum of allogeneic extracts when donor leucocytes came from married or transfused females or transfused males. Leucocytes from healthy (nontransfused) males showed no reaction with any of the extracts. As a period of cell culture was used prior to preparation of this extract to remove nonspecific inhibitory substances, native immunoglobulins, and complexes, the data are best explained by the presence of a foreign pathogen or altered cell component in the synovial cells of these rheumatoid patients.     

Evaluation of SV40-transformed synovial fibroblasts in the study of rheumatoid arthritis pathogenesis

The SV40 T antigen has been used to generate immortalized cells from rheumatoid arthritis (RA) synovial fibroblasts (RASFs) that are commonly used in lieu of primary RASFs. In the current study, we investigated the effect of stimulation by tissue necrosis factor alpha (TNF-α) and interleukin 17 (IL-17) on primary and immortalized RASFs in order to gauge the appropriateness of the use of immortalized RASFs, the MH7A cell line, in the study of RA pathogenesis. Changes in the levels of secretion and expression of 8 proteins associated with RA upon stimulation were assessed by multiplex immunoassay. IL-17 stimulation had a minimal impact on protein secretion and expression for primary and immortalized cells. Basic fibroblast growth factor (FGF-2) was not detectable for the primary cells but was detectable for the immortalized cells. In contrast, monocyte chemoattractant protein 1 (MCP-1) was detectable for primary cells but was undetectable for immortalized cells. In general, protein expression and secretion by cells stimulated with TNF-α were significantly increased. For primary cells, several proteins were below the limit of detection for unstimulated cells and cells stimulated with IL-17, while levels for TNF-α-stimulated cells were within the detectable range. For the same proteins, expression was observed for immortalized cells, regardless of stimulation, suggestive of constitutive activation of the NF-κB signaling pathway. The current study therefore provides strong evidence that immortalized and primary RASFs differ in regard to protein expression and secretion and therefore may not be appropriate for use in the study of RA pathogenesis.     

Targeting of cells involved in the pathogenesis of rheumatoid arthritis

The pathogenesis of rheumatoid arthritis (RA) is a consequence of the activation of T cells by as yet unknown antigens and the co-stimulatory molecules CD4 and CD28. A number of potential antigens have been proposed for this process, including type II collagen, heat shock proteins and the glycoprotein gp39. Following activation, T cells initiate the inflammatory cascade through secretion of either interleukin 2 (IL-2) or interferon gamma, or through direct cellular interaction with macrophages and synoviocytes. Targeted therapies in RA are predominantly directed against the T cell. Results of several trials of anti-CD4 antibodies are being evaluated, including those of an anti-IL-6 receptor antibody, which showed short-term effectiveness but some toxicity, and an anti-intercellular adhesion molecule 1 antibody that caused dramatic reduction in rheumatoid factor titres. Non-antibody therapies of RA being studied include nasal administration of gp39 and oral administration of type II articular collagen, but the results of these studies have been equivocal.     

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.     

类风湿关节炎患者滑膜树突状细胞的研究

目的　探讨滑膜树突状细胞在类风湿关节炎 (RA)中的作用。方法　采用免疫组织化学方法观察 2 5例RA滑膜中HLA DR抗原阳性表达细胞、S 10 0阳性CD1a阳性的树突状细胞(DC)的多少和分布情况。结果　 2 3例RA滑膜细胞HLA DR表达阳性 ,19例S 10 0表达阳性 ,16例CD1a表达阳性 ,其阳性例数的百分率均高于对照组。RA滑膜中HLA DR、S 10 0和CD1a标记阳性细胞数均明显高于对照组 ,其差异有非常显著意义 (P <0 0 1)。结论　RA滑膜中DC和被激活的DC及HLA DR阳性细胞的存在和增多可能在RA病变局部递呈自身抗原的过程中起重要的作用 ,是RA自身免疫异常的重要的始发因素