Biased t cell receptor v gene usage in rheumatoid arthritis. oligoclonal expansion of t cells expressing vα2 genes in synovial fluid but not in peripheral blood

Objective. To analyze the T cell receptor (TCR) variable (V) region gene usage in the rheumatoid joint. Methods. Monoclonal antibodies (MAb) were used to determine the prevalence of selected V elements on T cells in synovial fluid (SF) from rheumatoid arthritis (RA) patients and in peripheral blood (PB) from RA patients and normal controls. V_α2-positive PB and SF T cells from 1 patient were cloned by immediated limiting-dilution and analyzed by restriction mapping. Results. In 9 of 14 RA patients, SF was enriched in at least 1 of the selected V elements, compared with PB. TCR genes of the V_α2 family were the most frequently overrepresented in the SF (4 patients). The expanded V_α2-positive cells were oligoclonal in SF but heterogeneic in PB. Conclusion. Our data showing biased and clonally restricted TCR elements in the rheumatoid joint indicate major histocompatibility complex–restricted antigen recognition, rather than a “superantigen,” in the pathogenesis of RA.     

Increased frequency of vβ17-positive t cells in patients with rheumatoid arthritis

Objective. To identify the T lymphocytes that mediate disease in rheumatoid arthritis (RA). Methods. A panel of monoclonal antibodies reactive with T cell receptor (TCR) Vβ gene products was used to analyze the RA T cell repertoire. Results. Of 5 TCR Vβ gene products studied, only Vβ17-positive T cells were increased in peripheral blood and synovial fluid (SF) from RA patients, compared with controls (P < 0.01 and P = 0.0006, respectively). Thirty-one percent of the 49 RA SF samples and none of the 19 non-RA SF samples contained >10% Vβ17-positive T cells. Activated (Tac-positive) T cells were enriched among Vβ17-positive synovial T cells. Conclusion. The selective increase of Vβ17-positive T cells suggests a role for those T cells in the pathogenesis of RA.     

Reduction of leukocyte and interleukin-1β concentrations in the synovial fluid of rheumatoid arthritis patients treated with methotrexate

Objective. To examine the effect of methotrexate (MTX) on the numbers of leukocytes in the peripheral blood (PB) and synovial fluid (SF) of patients with active rheumatoid arthritis (RA). Methods. Twelve patients were treated with MTX; 5 patients not taking MTX served as controls. Samples of PB and SF were collected at 0, 1, 4, and 8 weeks of the study. Disease activity was scored, and total leukocytes, neutrophils, lymphocytes, and CD4+, CD8+, DR+, and CD25+ lymphocyte subsets were analyzed in PB and SF. Interleukin-1β (IL-1β) concentrations in SF were determined. Results. Patients treated with MTX showed significant clinical improvement. No change in PB leukocytes or lymphocyte subsets was observed in either patient group over the 8-week study period. In contrast, the number of leukocytes, the number and proportion of neutrophils, and the concentration of IL-1β in the SF of patients treated with MTX were reduced. In addition, in MTX-treated patients, there was an appreciable decrease in SF CD8+ lymphocytes, but not CD4+, DR+, or CD25+ lymphocytes. Conclusion. These findings suggest that in RA, MTX acts, at least in part, by reducing the migration of leukocytes into the inflamed synovium. Local reduction of IL-1β secretion may contribute to this effect.     

CD4+CD25+ regulatory T cells in rheumatoid arthritis: Differences in the presence,phenotype, and function between peripheral blood and synovial fluid

Objective

In mice, CD4+CD25+ regulatory T cells play a pivotal role in preventing autoimmunity. Regulatory T cells are also present and functional in healthy humans. We investigated the presence, phenotype, and function of CD4+CD25+ regulatory T cells in peripheral blood (PB) and synovial fluid (SF) from patients with rheumatoid arthritis (RA).

Methods

The presence and phenotype of CD4+CD25+ regulatory T cells were determined by flow cytometry. Anergy and suppressive activity were assessed by culturing CD4+CD25− and CD4+CD25+ T cells with anti‐CD3 monoclonal antibodies and antigen‐presenting cells, followed by proliferation and cytokine detection.

Results

The percentage of CD4+CD25+ T cells in RA SF was significantly increased compared with that in RA PB, and both of these percentages were higher than that in PB from controls. The cells in RA PB were similar in phenotype and function to CD4+CD25+ regulatory T cells from controls. In SF, however, ∼40–50% of CD4+CD25+ T cells expressed an activated phenotype, i.e., CD69+, class II MHC+, OX‐40+, with high levels of CTLA‐4 and glucocorticoid‐induced tumor necrosis factor receptor. These synovial CD4+CD25+ T cells displayed an increased suppressive capacity compared with blood CD4+CD25+ T cells. However, this enhanced suppressive activity was counterbalanced, because activated responder T cells from SF were less susceptible to CD4+CD25+ T cell–mediated suppression than were responder cells from PB.

Conclusion

We demonstrate that CD4+CD25+ regulatory T cells are present and functional in patients with RA, with higher numbers of regulatory T cells with increased suppressive activity found in SF compared with PB. These findings suggest a negative feedback system that is active at the site of inflammation. The balance between activated responder and regulatory T cells appears to influence the extent of immunoregulation in RA.

     

Mycobacteria and human heat shock protein—specific cytotoxic t lymphocytes in rheumatoid synovial inflammation

Objective. To study the cytotoxic capacity of mycobacteria-specific T lymphocyte lines and clones from sites of inflammation in patients with rheumatoid arthritis (RA). We also studied antigen specificity, surface phenotype, expression of T cell receptors (TCR), and HLA restriction. Methods. Autologous macrophages (Mπ) from the synovial membrane (SM), synovial fluid (SF), or peripheral blood (PB) were used as target cells in cytotoxicity assays. Results. All SM and SF cell lines tested thus far have shown specific lysis of the autologous Mπ from SM or PB that had been pulsed with BCG (bacillus Calmette-Guerin), but no cytotoxicity when the targets were pulsed with irrelevant antigens such as tetanus toxoid and Chlamydia. Both CD4+ and CD8+ cells were shown to be involved in the specific cytolysis. The majority of the cytotoxic T lymphocyte (CTL) lines were TCRα/β+ cells. However, both TCRα/β+ and TCRγ/δ+ clones (TCR δ1+) from one RA patient showed antigen-specific lysis. Antigen-specific recognition by a number of CTL lines and clones generated from SF and SM was restricted by HLA—DR molecules. Two Mycobacterium bovis 65-kd heat shock protein (HSP)–specific TCRα/β+ SF T cell clones also lysed Mπ that had been pulsed with a recombinant human 65-kd HSP. Conclusion. Joint inflammation and destruction might be partly attributable to a cross-reaction of mycobacteria-induced cytotoxic T cells with self HSP.     

Enrichment of differentiated CD45RBdim,CD27 – memory T cells in the peripheral blood,synovial fluid,and synovial tissue of patients with rheumatoid arthritis

Objective. To delineate in greater detail the phenotype of T cells that reside in the synovial tissue (ST) and synovial fluid (SF) of patients with rheumatoid arthritis (RA), in order to determine their precise differentiation status, and to determine whether the accumulation of these specific T cell subsets in these synovial compartments could be related to their capacity for transendothelial migration. Methods. Lymphocytes from normal subjects or from the peripheral blood (PB), ST, and/or SF of RA patients were phenotypically analyzed by flow cytometry. Normal PB CD4+ T cells were also characterized using an in vitro assay of transendothelial migration. Results. ST and SF were found to be enriched with memory (CD45RA-, CD45RO+, CD11a^bright, CD44^bright) and activated (CD69+) T cells. Moreover, ST and SF cells from RA patients were enriched in differentiated CD4+, CD45RB^dim, CD27- T cells, a subset of mature memory T cells that develops after prolonged antigenic stimulation. In addition, PB of some RA patients contained an increased number of CD4+, CD45RB^dim, CD27- T cells. The CD4+, CD11a^bright, CD44^bright memory T cells, which included the CD45RB^dim, CD27- more mature memory cells, exhibited an enhanced capacity for transendothelial migration that is likely to contribute to their enrichment in the rheumatoid synovium. Conclusion. RA patients manifest an increased number of mature memory T cells in the SF and ST, and some also have an increased number of these cells in PB that is likely to reflect chronic antigenic stimulation. The enrichment of these cells in the SF and ST reflects, in part, an enhanced capacity to migrate from the vascular space into inflamed tissue.     

Cd8high+ (CD57+) T cells in patients with rheumatoid arthritis

Objective. To investigate the development and T cell receptor (TCR) usage of CD8+, CD57+ T cells in rheumatoid arthritis (RA) patients. Methods. Three-color flow cytometry using monoclonal antibodies (MAb) to CD8, CD57 and different TCR V_β gene products. Results. The proportion of CD8+ T cells expressing CD57 (CD57/CD8) was significantly higher in RA patients compared with age-matched controls. Expanded TCR V_β populations were more frequent, and were found in both RA patient—derived CD8^high+(CD57+) and CD8+, CD57– populations. TCR V_β5+ and TCR V_β13+ expansions were present at high frequency (5 of 26 and 7 of 26, respectively). TCR V_β expansions in CD8^high+(CD57+) lymphocytes from RA patients were significantly larger than those in age-matched controls (expansion index 2.38 ± 0.28, n = 41 and 1.63 ± 0.09, n = 32, respectively), and were stable over time. Conclusion. RA leads to an increase in the frequency of expanded CD8+ T cell subsets expressing selected TCR, due to expansion of TCR V_β+ populations in CD8^high+(CD57+) T cells. Their restricted TCR usage suggests potential specificity for RA antigens and, therefore, a potential role in the pathogenesis of RA.     

Rheumatoid arthritis synovial macrophages express the Fas‐associated death domain–like interleukin‐1β–converting enzyme–inhibitory protein and are refractory to Fas‐mediated apoptosis

Objective

The chronic inflammation and progressive joint destruction observed in rheumatoid arthritis (RA) are mediated in part by macrophages. A paucity of apoptosis has been observed in RA synovial tissues, yet the mechanism remains unknown. The present study sought to characterize the expression of Fas, Fas ligand (FasL), and Fas‐associated death domain–like interleukin‐1β–converting enzyme–inhibitory protein (FLIP), and to quantify the apoptosis induced by agonistic anti‐Fas antibody, using mononuclear cells (MNC) isolated from the peripheral blood (PB) and synovial fluid (SF) of RA patients.

Methods

The expression of Fas, FasL, and FLIP and apoptosis induced by agonistic anti‐Fas antibody in MNC from the PB and SF of RA patients were determined by flow cytometry. Immunohistochemistry employing a monospecific anti‐FLIP antibody was performed on RA and osteoarthritis (OA) synovial tissue.

Results

CD14‐positive monocyte/macrophages from normal and RA PB and from RA SF expressed equivalent levels of Fas and FasL. Furthermore, unlike the CD14‐positive PB monocytes, RA SF monocyte/macrophages were resistant to the addition of agonistic anti‐Fas antibody. In contrast, both CD14‐positive PB and SF monocyte/macrophages were sensitive to apoptosis mediated by a phosphatidylinositol 3‐kinase inhibitor. Intracellular staining of the caspase 8 inhibitor, FLIP, in CD14‐positive SF monocyte/macrophages revealed a significant up‐regulation of FLIP compared with normal and RA PB monocytes. Immunohistochemical analysis of synovial tissue from RA and OA patients revealed increased FLIP expression in the RA synovial lining compared with the OA synovial lining. Furthermore, FLIP expression was observed in the CD68‐positive population in the RA synovial lining. Forced reduction of FLIP by a chemical inhibitor resulted in RA SF macrophage apoptosis that was enhanced by agonistic anti‐Fas antibody, indicating that FLIP is necessary for SF macrophage survival.

Conclusion

These data suggest that up‐regulation of FLIP in RA macrophages may account for their persistence in the disease. Thus, the targeted suppression of FLIP may be a potential therapeutic strategy for the amelioration of RA.

     

Selective lymphocyte chemokine receptor expression in the rheumatoid joint

Objective

In patients with rheumatoid arthritis (RA), chemokines and their receptors are important for lymphocyte trafficking into the inflamed joint. This study was undertaken to characterize the expression of chemokine receptors CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CXCR3, and CX₃CR1 in normal (NL) peripheral blood (PB), RA PB, and RA synovial fluid (SF).

Methods

Using flow cytometry, immunohistochemistry, and 2‐color immunofluorescence, we defined the expression of chemokine receptors on CD3+ T lymphocytes in RA synovial tissue (ST), RA SF, RA PB, and NL PB.

Results

The percentage of CD3+ lymphocytes expressing CCR2, CCR4, CCR5, and CX₃CR1 was significantly elevated in RA PB compared with that in NL PB, while the percentage of CD3+ lymphocytes expressing CCR5 was significantly enhanced in RA SF compared with that in NL and RA PB. In contrast, similar percentages of CD3+ lymphocytes in NL PB, RA PB, and RA SF expressed CCR6 and CXCR3. Immunohistochemistry of RA ST showed lymphocyte expression of CCR4, and 2‐color immunofluorescence staining revealed RA ST CD3+ lymphocytes intensely immunoreactive for CXCR3, suggesting that these 2 receptors may be particularly important for CD3+ lymphocyte trafficking to the inflamed joint. In comparisons of chemokine receptor expression on naive (CD45RA+) and memory (CD45RO+) CD3+ lymphocytes, there were greater percentages of memory CD3+/CD4+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD4+ lymphocytes in RA PB and RA SF, and greater percentages of memory CD3+/CD8+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD8+ lymphocytes in RA SF, suggesting receptor up‐regulation upon lymphocyte activation. In contrast, percentages of CD3+/CD8+ memory lymphocytes expressing CX₃CR1 were significantly less than percentages of naive CD3+/CD8+ lymphocytes in RA PB, suggesting that this receptor may be down‐regulated upon lymphocyte activation. A major difference between the RA PB and NL PB groups was significantly more CCR4+ memory leukocytes and memory CCR5+/CD3+/CD8+ lymphocytes in RA PB than NL PB, further suggesting that these receptors may be particularly important for lymphocyte homing to the RA joint.

Conclusion

These results identify CCR4, CCR5, CXCR3, and CX₃CR1 as critical chemokine receptors in RA.

     

T cell receptor vβ repertoire of double-negative α/β t cells in patients with systemic sclerosis

Objective. To analyze the T cell receptor V_β gene on double-negative (DN) α/β T cells, which are increased in number, on peripheral blood lymphocytes (PBL) from patients with systemic sclerosis (SSc). Methods. The DN α/β T cells were sorted by flow cytometry from PBL obtained from 3 patients with SSc. The V_β repertoire was analyzed by polymerase chain reaction. Results. Only 1 or 2 V_β genes (V_β5/7, 5, or 17) were predominantly expressed on DN α/β T cells from these 3 patients. Conclusion. The V_β repertoire on DN α/β T cells in PBL from patients with SSc is rather restricted.     

The response of T cells to interleukin‐6 is differentially regulated by the microenvironment of the rheumatoid synovial fluid and tissue

Objective

Interleukin‐6 (IL‐6) is a proinflammatory cytokine with regulatory effects on the survival and differentiation of T cells. It exerts its biologic function in 2 ways: by directly binding to the IL‐6 receptor (IL‐6R; CD126) or via trans‐signaling, in which soluble IL‐6R/IL‐6 complexes bind to the signaling component CD130. This study was undertaken to assess the expression and regulation of CD126 and CD130 and determine how these affect the response of CD4+ T cells to IL‐6 in the joints of patients with rheumatoid arthritis (RA).

Methods

Flow cytometry and immunofluorescence microscopy were used to determine the expression, function, and regulation of CD126 and CD130 in CD4+ T cells from the peripheral blood (PB), synovial fluid (SF), and synovial tissue of RA patients.

Results

Compared to the findings in RA PB, CD4+ T cells in the SF and synovial tissue expressed low levels of CD126. In contrast, whereas CD4+ T cell expression of CD130 was minimal in the SF, its level in the synovial tissue was high. Consistent with this phenotype, synovial tissue T cells responded to trans‐signaling by soluble IL‐6R/IL‐6 complexes, whereas no response was evident in CD4+ T cells from the SF. Down‐regulation of both receptor components in SF T cells could be explained by exposure to high levels of IL‐6. Increased levels of CD130 messenger RNA and protein in synovial tissue CD4+ T cells suggested that CD130 is up‐regulated locally. Among a range of cytokines tested, only IL‐10 induced CD130 expression in T cells.

Conclusion

The inflamed microenvironment in the synovial tissue maintains responsiveness to IL‐6 trans‐signaling through the up‐regulation of CD130 expression in CD4+ T cells, and this process may be driven by IL‐10.

     

CTLA‐4IG suppresses reactive oxygen species by preventing synovial adherent cell–induced inactivation of rap1, a ras family GTPASE mediator of oxidative stress in rheumatoid arthritis T cells

Objective

Oxidative stress contributes to the inflammatory properties of rheumatoid arthritis (RA) synovial T lymphocytes. This study was undertaken to investigate the mechanisms leading to production of reactive oxygen species (ROS) and oxidative stress in RA synovial T lymphocytes.

Methods

ROS production in T lymphocytes from the peripheral blood (PB) of healthy donors and from the PB and synovial fluid (SF) of RA patients was measured by ROS‐dependent fluorescence of 6‐carboxy‐2′,7′‐dichlorofluorescein. Rap1 GTPase activation was assessed by activation‐specific probe precipitation. Proliferation of RA PB and SF T lymphocytes was assayed by ³H‐thymidine incorporation. In some experiments, RA PB T cells were preincubated with autologous SF or with PB or SF adherent cells. Experiments were performed in the absence or presence of transwell membranes or CTLA‐4Ig fusion proteins. Short‐ and long‐term stimulations of healthy donor PB T lymphocytes were performed with inflammatory cytokines, in the absence or presence of activating anti‐CD28 antibodies.

Results

T lymphocyte ROS production and Rap1 inactivation were mediated by cell–cell contact with RA synovial adherent cells, and this correlated with T cell mitogenic hyporesponsiveness. CTLA4‐Ig blockade of synovial adherent cell signaling to CD28 T cells reversed the inhibition of Rap1 activity and prevented induction of ROS. Introduction of active RapV12 into T cells also prevented induction of ROS production. Coincubation of T cells with stimulating anti‐CD28 antibodies and inflammatory cytokines synergistically increased T cell ROS production.

Conclusion

Cell–cell contact between T cells and RA synovial adherent cells mediates Rap1 inactivation and subsequent ROS production in T lymphocytes following exposure to inflammatory cytokines. This process can be blocked by CTLA4‐Ig fusion protein.

     

T lymphocytes in the synovial fluid of patients with active rheumatoid arthritis display CD134-OX40 surface antigen.

OBJECTIVE: To assess the percentage of T lymphocytes, bearing CD134, a member of the TNF receptor superfamily, primarily found on autoreactive CD4+ T cells in the peripheral blood (PB) and synovial fluid (SF) of rheumatoid arthritis (RA) patients. METHODS: The surface expression of CD134 on SF and PB mononuclear cells was performed by flow cytometry in 25 RA patients and correlated to the disease activity. RESULTS: CD134 expression on CD3+, CD4+, CD8+ and CD25+ cells was higher in SF than in PB of RA patients (P < 0.001). No differences were observed in the percentage of CD134+/CD4+ T lymphocytes in the PB of RA patients and controls. Patients with active RA had significantly higher percentage of CD3+/CD134+, CD4+/CD 134+, CD8+/CD134+ and CD25+/CD 134+ than those with inactive disease. CONCLUSION: These findings suggest that CD134+ T cells are involved in the immunopathological process of RA synovitis, maybe mirroring some other autoimmune disease in which autoreactive T cell infiltrating the target tissues largely coexpress CD134.     

Rheumatoid synovium is enriched in CD45RBdim mature memory T cells that are potent helpers for B cell differentiation

Objective. To delineate the phenotype and function of synovial T cells in rheumatoid arthritis (RA). Methods. T cells from normal subjects or from RA peripheral blood (PB), synovial fluid (SF), or synovial tissue (ST) were analyzed phenotypically and functionally. Results. RA SF and ST T cells were found to be markedly enriched in CD45RA^dim, CD45RO+, CD45RB^dim mature memory cells, whereas in the PB, CD45RA^bright naive T cells were more frequent than CD45RO+ memory T cells, and only a minority were CD45RB^dim. SF and ST T cells proliferated less well and produced less interleukin-2 in response to mitogenic stimuli than did PB T cells. However, synovial T cells effectively promoted the production of Ig from normal B cells. Moreover, PB and synovial T cells differed in their capacity to down-regulate immunoglobulin production. Anti-CD3—stimulated PB T cells suppressed Ig production unless their proliferation was prevented with mitomycin C. In contrast, synovial T cells were potent helpers of B cell Ig production regardless of antecedent treatment with mitomycin C. To examine the relationship between the CD45RB^dim phenotype and B cell help, CD45RB^dim T cells were sorted from PB. As opposed to the findings with synovial T cells, suppression by control PB CD45RB^dim T cells was observed, but only when large numbers were employed. B cell Ig production was enhanced after treatment of PB CD45RB^dim T cells with mitomycin C. In contrast, healthy control sorted CD45RB^bright or sorted CD4+, CD45RO+, CD45RB^bright T cells did not support Ig secretion. After treatment with mitomycin C, both of these populations were more effective helpers of Ig production. Conclusion. RA synovium is enriched in differentiated CD45RB^dim memory T cells with potent helper activity and diminished capacity to down-regulate B cells, strongly implying an active role for these cells in the production of Ig in the synovium, and thus in the propagation of disease.     

Expansion and enhanced survival of natural killer cells expressing the killer immunoglobulin‐like receptor KIR3DL2 in spondylarthritis

Objective

The spondylarthritides (SpA) are strongly associated with possession of HLA–B27. We hypothesized that the expression of abnormal forms of HLA–B27 in SpA may have a pathogenic role through interaction with cells bearing natural killer (NK) receptors, in particular, killer immunoglobulin‐like receptor (KIR) KIR3DL2, a receptor for HLA–B27 homodimer (B27₂). We therefore undertook the present study to determine the number and function of NK and T cells bearing KIR3DL2 in SpA.

Methods

Expression of KIR3DL2 on NK and T cells was quantified in peripheral blood (PB) from 35 patients with SpA and 5 patients with juvenile enthesitis‐related arthritis (juvenile ERA); samples were compared with samples from healthy and rheumatoid arthritis (RA) controls. Paired synovial fluid (SF) was studied where available. Expression of other KIRs as well as activation, memory, and homing markers on KIR3DL2+ NK and T cells was quantified. NK cell survival was assessed using the apoptotic markers annexin V and 7‐aminoactinomycin D, and cytotoxicity by ⁵¹Cr release assay.

Results

In SpA, an increased number of PB and SF NK and CD4+ T cells expressed the KIR3DL2 receptor compared with controls. In ERA, KIR3DL2 expression was increased in PB and SF CD4 T cells (and SF NK cells) compared with RA controls. KIR3DL2+ NK cells had an activated phenotype, and were protected from apoptosis by culture with a cell line expressing B27₂. SpA PB mononuclear NK cells from SpA patients showed greater cytotoxicity than those from controls.

Conclusion

KIR3DL2 expression on NK cells and CD4 lymphocytes is increased in SpA and ERA. These cells are activated and may have a pathogenic role.

     

Proinflammatory mediator–induced reversal of CD4+,CD25+ regulatory T cell–mediated suppression in rheumatoid arthritis

Objective

We previously demonstrated that CD4+,CD25+ regulatory T (Treg) cells are present in increased numbers in the synovial fluid (SF) of rheumatoid arthritis (RA) patients and display enhanced suppressive activity as compared with their peripheral blood (PB) counterparts. Despite the presence of these immunoregulatory cells in RA, chronic inflammation persists. The purpose of the present study was to investigate whether particular proinflammatory mediators that are associated with RA could abrogate CD4+,CD25+ Treg–mediated suppression.

Methods

Monocyte phenotype was determined by flow cytometry and cytokine levels by enzyme‐linked immunosorbent assay. Magnetically sorted CD4+,CD25– and CD4+,CD25+ T cells derived from the PB and SF obtained from RA patients were stimulated alone or in coculture with anti‐CD3 monoclonal antibody (mAb) and autologous antigen‐presenting cells, in the absence or presence of anti‐CD28 mAb or the proinflammatory cytokines interleukin‐6 (IL‐6), tumor necrosis factor α (TNFα), or IL‐7.

Results

Monocytes from the SF of RA patients displayed increased expression of HLA class II molecules, CD80, CD86, and CD40 as compared with PB‐derived monocytes, indicating their activated status. Mimicking this increased costimulatory potential, addition of anti‐CD28 mAb to cocultures of CD4+,CD25– and CD4+,CD25+ T cells resulted in reduced CD4+,CD25+ Treg–mediated suppression in both PB and SF. Furthermore, IL‐7 and, to a limited extent, TNFα, both of which are produced by activated monocytes and were detected in SF, abrogated the CD4+,CD25+ Treg–mediated suppression. In contrast, IL‐6 did not influence Treg‐mediated suppression.

Conclusion

Our findings suggest that the interaction of CD4+,CD25+ Treg cells with activated monocytes in the joint might lead to diminished suppressive activity of CD4+,CD25+ Treg cells in vivo, thus contributing to the chronic inflammation in RA.