Selective accumulation of CCR5+ T lymphocytes into inflamed joints of rheumatoid arthritis

Chemokines and their receptors play critical roles in the selectiverecruitment of various subsets of leukocytes. Recent studieshave indicated that some chemokine receptors are differentiallyexpressed on T_h1 and T_h2 cells. However, available data concerningthe presence of T cells with a T_h1 or a T_h2 character and theexpression of chemokine receptors on infiltrating T cells inthe rheumatic joint are still limited. In this study, we investigatedthe expression of CC chemokine receptor 4 (CCR4) and CCR5, whichhave been shown to be preferentially expressed on T_h2 and T_h1respectively on T cells from rheumatoid arthritis (RA) patients.Although both CCR5⁺ and CCR4⁺ CD4⁺ T cell populations were observedin peripheral blood mononuclear cells from healthy controlsand osteoarthritis patients, these cell populations were decreasedin patients with active RA. In contrast, the vast majority ofsynovial fluid (SF) T cells from active RA patients expressedCCR5 but not CCR4. CCR5 ligands, MIP-1 and RANTES, were foundin RA SF at high levels. CCR5⁺ CD4⁺ T cells from SF mononuclearcells of RA patients produced IFN- but not IL-4 in responseto anti-CD3 stimulation in vitro. These results indicated thatdifferential expression of chemokine receptors plays a criticalrole for selective recruitment of pro-inflammatory T cells intothe joints of RA.     

CXCR3 and CCR5 ligands in rheumatoid arthritis synovium

The pathogenesis of rheumatoid arthritis (RA) may be mediated by Th1-type T cells. Since chemokine receptors CXCR3 and CCR5 are preferentially expressed on Th1 cells, we tested the expression and regulation of several chemokines, including those that signal through CXCR3 (interferon-gamma-inducible protein of 10 kDa, IP-10, CXCL10; and monokine induced by interferon-gamma, Mig, CXCL9) and CCR5 (macrophage inflammatory protein (Mip)-1 alpha, CCL3; and Mip-1 beta, CCL4) in RA synovial fluids, synovial tissues, and blood. Synovial fluid (SF) protein levels of IP-10 (32.1 +/- 10.5 ng/ml), Mig (15.0 +/- 6.4 ng/ml), Mip-1 beta (0.7 +/- 0.3 ng/ml), and Mip-1 alpha (0.8 +/- 0.1 ng/ml) were 100-, 50-, 25-, and 2-fold elevated in RASF compared to control SF (P < 0.001, P < 0.001, P < 0. 001, and P < 0.02, respectively). Tissue levels of IP-10, Mig, and Mip-1 beta were significantly higher in RA than in OA (P < 0.01). Serum levels of IP-10 (3.1 +/- 1.2 ng/ml) were higher in patients with seropositive RA compared to controls (1.2 +/- 0.2 ng/ml) (P < 0.02). There was a gradient of IP-10, Mig, Mip-1 alpha, and Mip-1 beta from the blood into the synovial fluid in RA. Infiltrating T cells around high endothelial venules in RA synovium and 90 +/- 3% of SF CD3(+)CD4(+) T cells expressed CXCR3, and 85 +/- 2% of SF CD3(+)CD4(+) T cells expressed CCR5. Chemokines, including IP-10, Mig, Mip-1 alpha, and Mip-1 beta, may participate in the selective recruitment of CCR5(+)CXCR3(+) T cells to the inflamed synovium.     

风湿性关节炎患者T细胞表达CCR5和CXCR3的三色流式细胞分析

目的 在单细胞水平上，研究类风湿性关节炎（RA）患者滑液及外周血中T淋巴细胞上CCR5及CXCR3的表达，并结合临床资料分析其在RA发病中的可能作用机制及临床应用。方法 分离15例RA患者的滑液单个核细胞（SFMC）、外周血单个核细胞（PBMC），及15正常人PBMC（对照），以三色荧光素标记物进行流式细胞术分析T细胞上CCR5及CXCR3的表达。结果 与PBMC相比较，RA患者SFMC中T细胞上CCR5及CXCR3的表达显著增高（特别是CCR5）；而CXCR3的表达个体差异较大；与正常人相比较，RA患者初发或活动期未治时，PBMC中CCR5及CXCR3的表达明显增多。CCR5及CXCR3的表达率与患者的ESR及CRP相关。结论 CCR5^ T细胞积聚在RA患者的病变关节内，且与RA的病情密切相关。     

Regulation of CCR5 expression and MIP-1alpha production in CD4+ T cells from patients with rheumatoid arthritis

Production of CCR5 expression and MIP-1alpha, a ligand of CCR5, by CD4+ T cells from patients with rheumatoid arthritis (RA) were studied. We analysed further the influence of IL-15 stimulation, CD40/CD40 ligand (CD40L) interaction and CCR5 promotor polymorphism. One hundred and fifty-five RA patients and another 155 age- and sex-matched healthy individuals were enrolled. Peripheral CD4+ and double negative (DN) T cells from patients had lower portions of CCR5, whereas synovial CD4+ and DN T cells showed a much higher CCR5 expression. IL-15 significantly up-regulated the expression of CCR5 on purified CD4+ T cells. CD40L expression on synovial CD4+ T cells was increased greatly in CCR5+ portions by IL-15. MIP-1alpha production by synovial CD4+ T cells was also enhanced by IL-15. Co-culture of CD40 expressing synovial fibroblasts with IL-15-activated synovial CD4+ T cells significantly increased MIP-1alpha production. Expression of CCR5 on patients' CD4+ T cells was not influenced by the promotor polymorphism of CCR5 gene. Taken together, these data suggest CCR5+CD4+ T cells infiltrate the inflamed synovium and IL-15 up-regulates CCR5 and CD40L expression further and enhance MIP-1alpha production in synovial CD4+ T cells. Production of MIP-1alpha by synovial fibroblasts is significantly increased by engagement of CD40 with CD40L. Synovial microenvironment plays a potential role in regulation of CCR5+CD4+ T cells in rheumatoid joints.     

FoxP3 mRNA splice forms in synovial CD4+ T cells in rheumatoid arthritis and psoriatic arthritis

Our aim was to elucidate the relative amount of the different splice forms of FoxP3 mRNA in CD4+ T cells in peripheral blood (PB) compared to synovial fluid (SF) in RA and PsA patients. FoxP3 mRNA was measured using a quantitative real-time PCR method. CD4+ T cells were isolated from 17 paired samples of PB and SF from RA and PsA patients, and PB from 10 controls. FoxP3fl and FoxP3Δ2 mRNA was significantly increased (6.7 and 2.1-fold, respectively) in PB CD4+ T cells from RA patients compared to controls. FoxP3fl and Δ2 mRNA in SF CD4+ T cells was increased compared to controls in sero-negative RA and PsA, but not in sero-positive RA patients, who had a high FoxP3 expression in both PB and SF. The FoxP3Δ2Δ7 mRNA was barely detectable in patient samples, and not at all in healthy individuals. We provide evidence of an increased expression of FoxP3 splice forms in synovial CD4+ T cells from RA patients. A skewed, high expression profile of FoxP3, but not CTLA-4, in sero-negative RA and PsA, indicates that synovial CD4+ T cells may represent unique subsets of T cells which have been induced locally or selectively recruited to the joint.     

Selective recruitment of CCR6-expressing cells by increased production of MIP-3 alpha in rheumatoid arthritis

Retroviral superantigens such as minor lymphocyte stimulating (Mls) antigen play an important role in the pathogenesis of acute graft-versus-host disease (GVHD). However, it remains unclear how exogenous bacterial superantigens modulate acute GVHD. In this study, we tested the effects of staphylococcal enterotoxin B (SEB) on the development of acute GVHD in a model involving the systemic transfer of parental C57Bl/6 spleen cells into BDF1 mice. SEB treatment suppressed the expansion of donor-derived T cells and blocked the decrease in the number of host cells. Impaired haematopoiesis was actually rescued by treatment with SEB. In SEB-treated mice, both spontaneous proliferation and IL-2 production in T cells were suppressed on day 2 after parental cell infusion. On day 21, the number of donor-derived CD4+ Vbeta8+ T cells markedly decreased in the spleen of SEB-treated mice. Donor-derived CD4+ T cells failed to proliferate in response to host alloantigens, and both donor- and host-derived T cells were unable to produce IL-2 in response to concanavalin A stimulation, suggesting that SEB treatment induced a general immunosuppressive state. Our results indicate that SEB treatment prevents the development of acute GVHD by leading to unresponsiveness of donor-derived T cells against host alloantigens in a Vbeta-restricted and unrestricted manner.     

类风湿性关节炎患者CD4+CD25+Foxp3+调节性T细胞检测及意义

目的:研究CD4 CD25 FoxP3 调节性T细胞在类风湿关节炎患者(RA)外周血中的比例改变,并探讨其在疾病进程中的意义.方法:选取活动期及稳定期RA患者,采用细胞内染色的流式细胞术及定量PCR的方法,分别在蛋白质和mRNA水平检测FoxP3表达,并与正常人进行比较.结果:RA患者CD4和CD25双阳性细胞所占比例与对照组没有明显差异,而活动期患者外周血CD4 CD25high和CD4 CD25 FoxP3 细胞明显低于稳定期和对照组(P＜0.05).FoxP3 mRNA表达水平与蛋白质表达水平变化相一致.结论:类风湿性关节炎活动期时CD4 CD25 FoxP3 调节性T细胞明显减少,这群调节性T细胞可能参与了类风湿性关节炎的病理进程.     

Clonal analysis of T cell infiltrates in synovial tissue of patients with rheumatoid arthritis

To investigate the possibility of the presence of disease-relevant, antigen-specific immune reactions in rheumatoid arthritis (RA), clonal diversity of the T cells in the synovial tissue was examined. T cells were directly cloned by in vitro stimulation with phytohemagglutin and interleukin 2 from both the peripheral blood and inflammatory synovial tissue. Their clonotypes were defined by analyzing rearrangement patterns of T cell receptor (TCR) beta and gamma chain genes using Southern blotting. In total, 111 clones from the synovial tissue (four patients) and 45 from the peripheral blood (one patient) were studied. Although most of the clones were unique in their TCR gene rearrangement patterns, 2 clones from the synovial tissue of one patient had identical patterns. These 2 clones were CD3+, 4-, 8+. Since phenotypic analysis of 82 clones from the synovial tissues revealed that CD8+ T cell clones were less frequent (24%) than CD4+ clones, the clonal identity observed here in 2 clones may not be negligible. Furthermore, 1 CD8+ clone from the peripheral blood of the same patient also had the same clonotype. These results may suggest selective trafficking or proliferation of CD4-, CD8+ T cells in RA synovial tissue.     

The presence of cytokine-suppressive CD4+CD25+ T cells in the peripheral blood and synovial fluid of patients with rheumatoid arthritis

CD4+CD25+ T cells have been shown to play a regulatory or suppressive role in the immune response and are possibly relevant to the pathogenesis of autoimmune diseases. In the present study, we attempted to investigate the levels of CD4+CD25+ T cells in the peripheral blood (PB) and synovial fluid (SF) of patients with rheumatoid arthritis (RA) and the effects of CD4+CD25+ T cells on the in vitro cytokine production by stimulated SF mononuclear cells (SFMC). The results showed that RA patients had similar frequencies of CD4+CD25+ T cells in PB, expressed as a percentages of the lymphocyte population, as did healthy subjects (mean +/- SD: 10.52 +/- 5.87% versus 11.11 +/- 4.58%., respectively). But in contrast to PB, the SF of RA patients contained significantly higher levels of CD4+CD25+ T cells (17.77 +/- 7.92% versus 10.52 +/- 5.87%, respectively. P < 0.001). When cocultured in vitro with SFMC, CD4+CD25+ T cells purified from either PB or SF were found to exert a considerable suppressive effect on the production of cytokines including TNF-alpha, IFN-gamma and interleukin-10 (IL-10). The percentages of inhibition of each cytokines ranged from 41.8 to 98.4% (mean, 80.0%) for TNF-alpha, 42.8 to 98.9% (mean, 83.2%) for IFN-gamma and 59.3 to 96.6% (mean, 80.0%) for IL-10. Because both pro-inflammatory and anti-inflammatory cytokines were suppressed by CD4+CD25+ T cells, whether CD4+CD25+ T cells might play a beneficial role in the suppression of sustained inflammation in rheumatoid synovium remains to be elucidated.     

Evidence for the continuous recruitment and activation of T cells into the joints of patients with rheumatoid arthritis

Rheumatoid arthritis (RA) synovial fluid (SF) T cells express the activation markers CD69, HLA-DR and very late antigen (VLA)-1, but surprisingly few bear interleukin-2 receptors (CD25). This unusual activation state is commonly assumed to be due to stimulation by local antigen, yet T cells activated in vitro express activation antigens in the clearly defined sequence: CD69, CD25, HLA-DR and finally VLA-1. Two possible explanations for the activation state of SF cells are: first, they comprise several subpopulations each expressing different activation antigens or, second, activation markers are up-regulated by mechanisms other than antigen stimulation. To examine these hypotheses, double- and triple-color immunofluorescence techniques were applied to four T cell populations: normal peripheral blood T cells activated in vitro, RA SF T cells, T cells from an in vivo model of migration [tuberculin purified protein derivative (PPD)-induced skin blisters] and T cells co-cultured with endothelial cells (EC). The results confirmed that in vitro activated T cells expressed activation markers in the sequence described above, with significant CD25 expression and few cells co-expressing CD69 with HLA-DR or VLA-1. In contrast, almost half the SF T cells were CD69⁺HLA-DR⁺ but CD25^?; a significant minority were CD69⁺VLA^?l⁺, T cells from PPD-induced skin blisters were already HLA-DR⁺ and VLA-1⁺ at 24 h, although, in vitro, PPD-activated T cells up-regulated HLA-DR and VLA-1 only after 1 week, suggesting that pre-activated T cells were preferentially recruited into the blisters. Finally, T cells were found to up-regulate CD69 and, to a lesser extent, HLA-DR after adhering to EC in vitro. In summary, the paradoxical activation state of SF T cells cannot be explained solely by single or multiple rounds of activation in situ. At least two other mechanisms, the preferential recruitment of pre-activated T cells and the induction of HLA-DR and especially CD69 by endothelial contact during migration, may also play a role.     

Lack of T cell oligoclonality in enzyme-digested synovial tissue and in synovial fluid in most patients with rheumatoid arthritis.

The dominant presence of specific T-cell populations in the rheumatoid joint as detected by Southern blot analysis of T cell receptor (TCR) gene rearrangements would indicate local antigen recognition and T cell proliferation. We therefore studied TCR beta chain gene rearrangements using a C beta 2 probe in paired samples of T cell populations from synovial tissue and peripheral blood (n = 6) as well as synovial fluid (n = 16) and peripheral blood (n = 18) of patients with rheumatoid arthritis (RA). Peripheral blood mononuclear cells from healthy donors (n = 7) served as a control. T cells were studied directly after isolation or after non-specific expansion with OKT3 monoclonal antibody (MoAb) and T cell growth factor (TCGF). DNA samples were digested with EcoRI and HindIII to detect rearrangements to C beta 1 and C beta 2, respectively. Extra bands were detected in all EcoRI-digested DNA samples prepared from both freshly isolated and non-specifically expanded T cell populations of patients and healthy donors, possibly representing 'common' (V-) D-J rearrangements. Dominant rearrangements were found in only two out of 16 synovial fluid T cell populations (one freshly isolated and one expanded) and not in peripheral blood or synovial tissue derived T cell populations. No extra bands were detected in HindIII-digested DNA samples. To investigate the effect of in vitro culture techniques on rearrangement patterns we studied DNA samples prepared from synovial tissue T cells obtained both by outgrowth from tissue with TCGF or by enzyme digestion and subsequent expansion either with TCGF or with OKT3 MoAb and TCGF. Whereas the latter T cell population yielded 'common' rearrangements, the former T cell populations yielded different dominant rearrangements. These data indicate that oligoclonality of the T cell populations in synovial tissue and synovial fluid of patients with RA is a rare event. The data also show the influence of in vitro culture techniques on the result of TCR gene rearrangement analysis.     

Chemokine and chemokine receptor analysis reveals elevated interferon-inducible protein-10 (IP)-10/CXCL10 levels and increased number of CCR5+ and CXCR3+ CD4 T cells in synovial fluid of patients with enthesitis-related arthritis (ERA)

Chemokines and chemokine receptors play a major role in homing of cells to the site of inflammation. Enthesitis-related arthritis (ERA) is a chronic inflammatory arthritis and no data are available on chemokines and their receptors in ERA. Blood (20) and synovial fluid (SF) (11) was collected from patients with ERA, and peripheral blood (PB) was collected from 12 patients with polyarticular juvenile idiopathic arthritis (JIA), nine patients with systemic onset and 18 healthy controls. Chemokines [interleukin (IL)-10/CXCL10, thymus and activation-regulated chemokine (TARC)/CCL17 and regulated upon activation normal T cell expressed and secreted (RANTES)/CCL5] were measured in serum and SF. Chemokine receptor expression was measured by flow cytometry. There was no difference in blood CD4(+) T cells bearing CCR5, CCR4 and CXCR3 in ERA and healthy controls. In paired samples the median frequency of CCR5(+) CD4(+) T cells was higher in SF compared to PB (15.8 versus 3.9%, P < 0.005), as was the frequency of CXCR3(+) T cells (21.61% versus 12.46%, P < 0.05). Median serum interferon-inducible protein-10 (IP-10)/CXCL10 levels were higher in patients with ERA compared to controls (139 versus 93 pg/ml; P < 0.05). Further median SF IP-10/CXCL10 levels were higher than the serum levels (2300 pg/ml versus 139 pg/ml; P < 0.01). Serum levels of RANTES/CCL5 were higher in patients (150 ng/ml) compared to control (99 ng/ml; P < 0.01). The SF levels were significantly lower compared to serum (P < 0.05). TARC/CCL17 levels in SF were lower than serum. There is increased homing of CCR5 and CXCR3(+) CD4 cells to the SF. Increased SF levels of IP-10/CXCL10 may be responsible for this migration in patients with ERA.     

类风湿关节炎患者外周血和滑液中CD4~+CD25~+调节性T细胞的水平变化

了解具有抑制功能的CD4+CD25+调节性T细胞(Treg)在类风湿关节炎(RA)中的水平变化。分离32例RA患者及35例正常对照者外周血和15例RA关节滑液中的单个核细胞,用荧光抗体标记细胞膜表面CD4、CD25分子和细胞内Foxp3转录因子,进行流式细胞分析,同时用RT-PCR方法测定单个核细胞中Foxp3 mRNA水平。实验发现RA外周血中CD4+CD25hT细胞比例(1.90±1.68)与健康人(1.81±1.79)无明显差异,而RA关节滑液中CD4+CD25+和CD4+CD25hT细胞含量却明显增高(14.98±12.52,8.94±9.67,P<0.01)。RA患者外周血单个核细胞中Foxp3+/CD4+T细胞比值(2.35±2.06)较正常人(7.25±3.98)明显降低(P<0.01),RA外周血中Foxp3 mRNA含量较正常人Treg减少,而RA关节液中Foxp3 mRNA含量较RA外周血更为低下(P<0.01)。RA患者存在CD4+CD25+Treg的异常改变,其外周血和关节液中具有抑制作用的Treg含量明显降低提示RA患者Treg数量减少及抑制功能下降可能是RA自身免疫反应亢强不能控制的原因之一。RA关节液中CD4+CD25hT细胞增高考虑与RA炎症反应造成T细胞过度活化有关。     

Elevated circulating Th17 and follicular helper CD4+ T cells in patients with rheumatoid arthritis

It remains not fully elucidated the potential functions of Th17 cells and follicular helper T (Tfh) cells and secreting cytokines in the pathogenesis of rheumatoid arthritis (RA) and their association with disease activity. In this study, the frequencies of Th17 and Tfh cells were determined by flow cytometry, and the levels of interleukin (IL)‐17, IL‐21, and IL‐22 were measured by ELISA in RA patients with different disease activities. The dynamic changes of cell subsets were also detected in response to disease‐modify antirheumatic drugs (DMARDs) therapy. The percentages of CD3⁺CD4⁺IL‐17A⁺ (Th17) cells and CD3⁺CD4⁺CXCR5⁺ICOS^high (Tfh) cells, as well as the concentrations of IL‐17, IL‐21, and IL‐22 were significantly elevated in RA patients than those in healthy individuals. Furthermore, Tfh cells, IL‐21, and IL‐22 in the serum was positively correlated with the values of disease activity score. Concentrations of IL‐21 and IL‐22 in the serum were remarkably reduced following the DMARDs therapies. Our data suggested that Th17 cells, Tfh cells as well as the secreting cytokines may be involved in the pathogenesis of RA. The frequency of circulating Tfh cells and the productions of IL‐21 and IL‐22 were associated with the disease activity of RA patients, and might be potential therapeutic targets for treatment of RA.     

Expression of TIM‐3 on CD4+ and CD8+ T cells in the peripheral blood and synovial fluid of rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by a chronic inflammatory process that targets the synovial lining of diarthrodial joints. TIM‐3 plays a key role in the negative regulation of the immune response. In this study, we investigated the expression of TIM‐3 on CD4+ and CD8+ T cells from systemic (peripheral blood) and local (synovial fluid) perspectives of RA. Level of TIM‐3+ cells from peripheral blood and synovial fluid of patients as well as peripheral blood of healthy controls was measured by flow cytometry. Results showed that TIM‐3 expression was significantly increased in both CD4+ and CD8+ T cells in the peripheral blood of RA (p < 0.001 and p < 0.001, respectively). Furthermore, patients revealed even higher expression of TIM‐3 in CD4+ and CD8+ T cells in synovial fluid than in peripheral blood. When comparing TIM‐3 level with the severity of RA, we identified that the percentage of TIM‐3 on both peripheral CD4+ and peripheral CD8+ T cells was negatively correlated with disease activity score 28 (DAS28) of the patients. Similarly, TIM‐3 on synovial fluid CD4+ and CD8+ T cells also revealed inverse correlation with DAS28 of the cases. Our data demonstrate a negative correlation between TIM‐3 and the disease progression of RA.     

Lack of preferential Vβ usage in synovial T cells of rheumatoid arthritis patients

The T-cell receptor Vβ subfamily repertoires of synovial and peripheral T cells of 8 rheumatoid arthritis (RA) patients were determined using the polymerase chain reaction. Three normal controls were included. Some of the rheumatoid synovial samples did not express the complete range of Vβ families and lacked as many as 6 gene families. However, these patients showed considerable individual variation in expression. Overall, the data do not support preferential T-cell receptor Vβ usage in synovial T cells of RA patients either in comparison to their autochthonous peripheral T cells or to peripheral T cells of normal subjects.     

类风湿关节炎患者Th17细胞与调节性T细胞失衡的研究

目的观察类风湿性关节炎（RA）患者外周血Th17细胞与CD4^＋CD25^＋FoxP3^＋调节性T细胞（Treg）平衡状态与疾病的关系,分析Th17／Treg细胞免疫失衡在RA发病机制中的作用。方法采用流式细胞仪四色荧光抗体标记法分别对47例RA患者和39名健康志愿者（HVs）进行CD3、CD8、IL-17与CD4、CD25、F0xP3标记,测定Th17与调节性T细胞的比例变化及相关细胞因子IL-6、IL-23和IL-17水平。结果RA组患者外周血中,CD3^＋CD8^＋IL-17^＋T细胞占CD3^＋T淋巴细胞的百分比为（1．12±0．38）％,明显高于对照组（0．68±0．29）％（t=1．83,P〈0．05）;CD4’CD25’FoxP3^＋细胞占CD4^＋T淋巴细胞的百分比为（2．74±0．71）％,明显低于对照组（4．69±1．23）％（t=-2．94,P〈0．05）。相关细胞因子测定结果：IL-6水平在RA组为（13．5±3．7）ng／L,正常人为（4．6±0．9）ng／L（t=6．24,P〈0．01）;IL-23水平在RA组为（71±19）ng／L,正常人为（25±6）ng／L（t=14．37,P〈0．01）;IL-17水平在RA组为（122±33）ng／L,正常人为（37±9）ng／L（t=19．01,P〈0．01）;RA患者血清IL-6、IL-23和IL-17水平均明显升高。结论RA患者外周血Th17与CD4^＋CD25^＋FoxP3^＋调节性T细胞数量的异常可能是RA发病的重要因素,IL-6和IL-23的升高是引起这些改变的可能原因。     

A study of opioid peptides in synovial fluid and synovial tissue in patients with rheumatoid arthritis]

Authors have often experienced that psychological stress influences rheumatoid arthritis (RA). In addition, recent reports show a modulatory role for neuropeptide such as substance P in arthritis. These findings prompted us to study endogenous opioid peptides in RA, which are found mainly in the brain and have an effect on the central nervous system. We examined methionine-enkephalin (Met-enk), leucine-enkephalin (Leu-enk) and beta-endorphin (beta-end) in opioid peptides. We measured these peptides in plasma and synovial fluid samples obtained from 28 knees of 24 RA patients and the quantity in the synovial tissue of 13 knees. We also measured plasma and synovial fluid samples from patients with osteoarthritis of the knee and plasma samples from healthy candidates. Leu-enk and beta-end levels in synovial fluid were significantly higher than plasma levels only in RA. Larger quantity of Leu-end and beta-end were contained apparently in the synovial tissue than Met-enk. The synovial tissue with proliferative change tends to contain larger quantity of opioid peptides. These results indicate that the synovial tissue produces or secretes Leu-enk and beta-end and that opioid peptides are related to the degree of inflammation in RA.