Prediction of Response to Targeted Treatment in Rheumatoid Arthritis.

Rheumatoid arthritis is an autoimmune syndrome presenting with chronic inflammation of the joints. Patients with the same diagnosis can present with different phenotypes. In some patients severe joint inflammation and early joint destruction are observed, whereas a milder phenotype can be seen in others. Conversely, patients with the same signs and symptoms may exhibit different immunological and molecular abnormalities. Since the introduction of early treatment in clinical practice, the treat to target principle, and new medicines such as biologic disease-modifying antirheumatic drugs, clinical remission can be achieved early in the disease course, albeit not in all patients. The clinical response and efficacy of biologic disease-modifying antirheumatic drugs vary among different individuals. Therefore, there is a need to develop a more personalized approach toward treatment to achieve rapid remission in every patient to prevent disability and restore and maintain quality of life, without unnecessary adverse effects, in a cost-effective manner. The latest data from explorative studies of predictive markers of response are discussed here, together with a preliminary treatment algorithm based on currently available knowledge.

Treatment-specific changes in circulating adipocytokines: a comparison between tumour necrosis factor blockade and glucocorticoid treatment for rheumatoid arthritis.

OBJECTIVE: There is increasing evidence that adipocytokines may exert proinflammatory and destructive effects in rheumatoid arthritis (RA). Hence, the authors investigated the relationship between adipocytokines and several features associated with RA (inflammation, joint destruction and cardiovascular disease), as well as the effect of treatment with a tumour necrosis factor inhibitor or glucocorticoids (GCs) hereupon. METHODS: Serum levels of adiponectin, leptin, resistin, visfatin, vaspin and lipids were determined in a well-defined cohort of patients with RA before and after 16 weeks of adalimumab treatment (adalimumab cohort). The same parameters were analysed in two other cohorts of patients with RA before and after 2 weeks of high-dose prednisolone (high GC cohort) and before and after 22 weeks of treatment with a combination regimen with tapered high-dose prednisolone (COBRA -GC cohort). Radiographs of hands and feet (adalimumab and COBRA-GC cohorts) were assessed at baseline and after treatment. RESULTS: Treatment with adalimumab or GC showed opposing effects on vaspin and visfatin levels. Lipid levels improved after several months of adalimumab or GC treatment; in the adalimumab cohort, this was related to reduced visfatin levels, independent of C reactive protein levels. After long-term adalimumab or GC treatment, resistin levels declined, which was associated with a decrease in inflammation markers. In the adalimumab cohort, baseline resistin levels were predictive of baseline radiological damage, independent of anticitrullinated peptide antibodies status or C reactive protein levels. CONCLUSION: Changes in serum adipocytokine levels were treatment specific, further strengthening the role of visfatin and resistin in several disease manifestations of RA.

Venous and arterial thromboembolic events in adalimumab-treated patients with antiadalimumab antibodies: a case series and cohort study.

OBJECTIVE: We observed 3 patients who developed severe venous and arterial thromboembolic events during treatment with adalimumab, 2 of whom had rheumatoid arthritis (RA) and 1 of whom had psoriatic arthritis. Antiadalimumab antibodies were detected in all 3 patients. We undertook this study to determine whether the development of antiadalimumab antibodies was associated with thromboembolic events during adalimumab treatment. METHODS: A retrospective search (with blinding with regard to antiadalimumab antibody status) for thromboembolic events was performed in a prospective cohort of 272 consecutively included adalimumab-treated RA patients. Incidence rates were calculated and hazard ratios (HRs) were estimated using Cox regression. None of the index patients were part of the cohort. RESULTS: Antiadalimumab antibodies were detected in 76 of 272 patients (28%). Eight thromboembolic events were found, 4 of which had occurred in patients with antiadalimumab antibodies. The incidence rate was 26.9/1,000 person-years for patients with antiadalimumab antibodies and 8.4/1,000 person-years for patients without those antibodies (HR 3.8 [95% confidence interval 0.9-15.3], P = 0.064). After adjustment for duration of followup, age, body mass index, erythrocyte sedimentation rate, and prior thromboembolic events, the HR was 7.6 (95% confidence interval 1.3-45.1) (P = 0.025). CONCLUSION: These findings suggest that the occurrence of venous and arterial thromboembolic events during adalimumab treatment is higher in patients with antiadalimumab antibodies than in those without antiadalimumab antibodies. Patient numbers were relatively small; therefore, validation in other cohorts is mandatory.

Monocyte migration to the synovium in rheumatoid arthritis patients treated with adalimumab.

OBJECTIVES: The mechanism of action of treatment with tumour necrosis factor (TNF) blockers in rheumatoid arthritis (RA) is still not completely understood. The aim of this study was to test if adalimumab treatment could affect the influx of monocytes into the synovium. METHODS: A novel technique was used to analyse the migration of labelled autologous monocytes before and 14 days after initiation of adalimumab treatment using scintigraphy. CD14 monocytes were isolated from patients with RA, using a positive selection procedure with magnetic-activated cell sorting, and labelled with technetium-99m-hexamethylpropylene-amino-oxime. Scintigraphic scans were made 1, 2 and 3 h after re-infusion. RESULTS: As early as 14 days after the start of treatment with adalimumab a significant decrease in disease activity score evaluated in 28 joints was shown. There was no significant decrease in the influx of monocytes into the joint at this time. CONCLUSIONS: This study indicates that adalimumab treatment does not reduce the influx of monocytes into the synovium early after initiation of treatment. As previous studies showed a rapid decrease in macrophage infiltration after TNF-antibody therapy, which could not be explained by increased cell death, this points to an important role for enhanced efflux of inflammatory cells from the synovium.

Pharmacogenomics of infliximab treatment using peripheral blood cells of patients with rheumatoid arthritis.

To provide insight into the pharmacological changes in the peripheral blood (PB) molecular profile induced by tumor necrosis factor (TNF)-blockade in patients with rheumatoid arthritis (RA), blood was obtained in PAXgene tubes from 33 RA patients before and 1 month after TNF-blocking therapy (infliximab). From 15 randomly chosen patients pre- and post-treatment gene expression profiles were determined. The remaining 18 RA patients served as validation cohort. A group-based paired analysis of the gene expression profiles from the post- vs pre-treatment samples revealed a signature of genes significantly regulated by TNF-blockade. Downregulated genes reflected several biological pathways such as inflammation, angiogenesis, B- and T-cell activation. Further analysis revealed that the pharmacological response signature was significantly regulated in all treated patients, irrespective of clinical response, which is indicative for the presence of an active TNF pathway in all RA patients. The data imply that all patients carried features of TNF bioactivity irrespective of clinical response. These results favor a model for the parallel presence of TNF-dependent and TNF-independent pathways in the individual RA patient. Clinical response status to TNF-blockade may be dependent on the relative contribution of TNF-independent effector pathways.

Anti-infliximab and anti-adalimumab antibodies in relation to response to adalimumab in infliximab switchers and anti-tumour necrosis factor naive patients: a cohort study.

OBJECTIVE: To investigate how antibodies against anti-tumour necrosis factor (anti-TNF) agents influence response after switching from infliximab to adalimumab in rheumatoid arthritis (RA). METHODS: This cohort study consisted of 235 patients with RA, all treated with adalimumab. At baseline 52 patients (22%) had been previously treated with infliximab ('switchers'), and 183 (78%) were anti-TNF naive. Disease activity (using the 28-joint count Disease Activity Score (DAS28)) and presence of antibodies against infliximab and adalimumab were assessed. Clinical response to adalimumab was compared between switchers and anti-TNF naive patients and their anti-infliximab and anti-adalimumab antibody status. RESULTS: After 28 weeks of adalimumab treatment the decrease in DAS28 (Delta DAS28) for the 235 patients was 1.6+/-1.5 (mean+/-SD). Anti-adalimumab antibodies were detected in 46 patients (20%). Delta DAS28 was 1.8+/-1.4 in patients without anti-adalimumab and 0.6+/-1.3 in patients with anti-adalimumab (p<0.0001). Thirty-three of the 52 switchers (63%) had anti-infliximab antibodies. Patients with anti-infliximab more often developed anti-adalimumab than anti-TNF naive patients (11 (33%) vs 32 (18%); p=0.039). Delta DAS28 was greater for anti-TNF naive patients (1.7+/-1.5) than for switchers without anti-infliximab antibodies (Delta DAS28=0.9+/-1.4) (p=0.009). Delta DAS28 for switchers with anti-infliximab was 1.2+/-1.3 and did not differ significantly from anti-TNF naive patients (p=0.262). CONCLUSION: Switchers with anti-infliximab antibodies more often develop antibodies against adalimumab than anti-TNF naive patients. Response to adalimumab was limited in switchers without anti-infliximab antibodies, which raises the question whether a second anti-TNF treatment should be offered to patients with RA for whom an initial treatment with an anti-TNF blocker fails, in the absence of anti-biological antibodies.

TWEAK and its receptor Fn14 in the synovium of patients with rheumatoid arthritis compared to psoriatic arthritis and its response to tumour necrosis factor blockade.

OBJECTIVE: To investigate the expression of tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor inducible 14 (Fn14) in the inflamed synovium of patients with arthritis, as TWEAK blockade has been observed to have a beneficial effect in an animal model of rheumatoid arthritis (RA). METHODS: Synovial tissue (ST) biopsies were obtained from 6 early, methotrexate-naive patients with RA as well as 13 patients with RA and 16 patients with psoriatic arthritis (PsA) who were matched for treatment and disease duration. Serial ST samples were obtained from a separate cohort of 13 patients with RA before and after infliximab treatment. TWEAK and Fn14 expression was evaluated by immunohistochemistry and digital image analysis. RESULTS: TWEAK and Fn14 were clearly expressed in ST of patients with RA and PsA. TWEAK expression was significantly higher in RA (sub)lining samples compared to PsA (p = 0.005 and p = 0.014, respectively), but Fn14 expression was comparable. Double immunofluorescence showed TWEAK and Fn14 expression on fibroblast-like synoviocytes and macrophages, but not T cells. Of interest, persistent TWEAK and Fn14 expression was found after anti-TNF therapy. CONCLUSIONS: TWEAK and Fn14 are abundantly expressed in the inflamed synovium of patients with RA and PsA. This raises the possibility that blocking TWEAK/Fn14 signalling could be of therapeutic benefit in inflammatory arthritis.

Perceived work ability, quality of life, and fatigue in patients with rheumatoid arthritis after a 6-month course of TNF inhibitors: prospective intervention study and partial economic evaluation.

OBJECTIVE: The objective of this exploratory study was to evaluate the effects and costs of a 6-month course of tumour necrosis factor (TNF) inhibitors on work ability, quality of life, and fatigue in patients with rheumatoid arthritis (RA). METHODS: In this prospective single-arm intervention study 59 consecutive patients of working age with established RA were recruited from an outpatient clinic in Amsterdam, the Netherlands. All patients received fortnightly subcutaneous injections of 40 mg adalimumab. The three outcomes at baseline and 6 months were: perceived work ability [Work Ability Index (WAI)], quality of life [Rheumatoid Arthritis Quality of Life instrument (RAQoL)], and fatigue [Checklist Individual Strength (CIS), Need for Recovery (NFR) scale]. Cost data of the preceding 6 months were collected using a self-administered patient questionnaire at baseline and follow-up. RESULTS: At 6 months, all outcomes showed a statistically significant improvement in mean scores from baseline, ranging from 10.0% (WAI), to 11.7% (RAQoL), to 15% (NFR) (subgroup paid work, n = 26). The total mean costs showed a twofold increase in mean costs per week per patient [difference EUR 169, 95% confidence interval (CI) EUR 113-226]. CONCLUSIONS: In this short-term exploratory evaluation, a 6-month course of TNF inhibitors improved work ability and quality of life, and reduced fatigue in patients with established RA. These effects are associated with an increase in total healthcare costs, attributable to the costs of TNF inhibitors. Randomized controlled trials with a longer follow-up are needed to show a long-term effect on work disability and the potential cost-effectiveness of TNF inhibitors.

Exposure to nuclear antigens contributes to the induction of humoral autoimmunity during tumour necrosis factor alpha blockade.

OBJECTIVE: Type I interferons and apoptotic particles contribute to antinuclear autoimmunity in experimental models. This study assessed whether similar mechanisms contribute to break peripheral B-cell tolerance in humans by studying the induction of antinuclear antibodies by tumour necrosis factor blockade in spondyloarthritis. METHODS: 40 spondyloarthritis patients treated with infliximab or etanercept and 20 renal cell carcinoma patients treated with sorafenib were studied. Serum antinucleosome IgM and nucleosomes were measured by ELISA. Type I interferon serum activity was measured using a functional reporter cell assay. Synovial apoptosis was assessed by terminal transferase nick end-labelling (TUNEL) assay and anti-active caspase-3 immunostaining. Complement was measured by nephelometry. RESULTS: Despite a similar clinical improvement and reduction of synovial inflammation, antinucleosome IgM were induced by infliximab but not etanercept. This induction did not correlate with type I interferon activity, which was transiently downmodulated by infliximab but persistently upregulated by etanercept. In contrast, antinucleosome IgM levels did correlate with serum nucleosome levels, which were significantly upregulated by infliximab but not by etanercept treatment. This increase in serum nucleosome levels was not directly related to massive cell death, but rather to a decrease of complement 3 and 4 serum levels during infliximab treatment. CONCLUSION: Infliximab and etanercept have a differential effect on both type I interferon activity and nucleosome levels. Only elevated serum nucleosomes relate to the induction of antinucleosome antibodies after infliximab treatment.

Bone mineral density in rheumatoid arthritis patients 1 year after adalimumab therapy: arrest of bone loss.

OBJECTIVE: To explore the effects of anti-tumour necrosis factor (TNF)alpha antibody therapy on bone mineral density (BMD) of the lumbar spine and femur neck in patients with rheumatoid arthritis (RA). METHODS: A total of 50 patients with active RA (DAS28> or =3.2) who started adalimumab (40 mg subcutaneously/2 weeks) were included in an open label prospective study. All patients used stable methotrexate and were allowed to use prednisone (< or =10 mg/day). The BMD of the lumbar spine and femur neck was measured before and 1 year after start of treatment. RESULTS: Disease activity at baseline (28-joint Disease Activity Score (DAS28)) and disease duration were inversely correlated with femoral neck BMD and lumbar spine BMD (p<0.05). Mean BMD of lumbar spine and femur neck remained unchanged after 1 year of adalimumab therapy (+0.3% and +0.3%, respectively). Of interest, a beneficial effect of prednisone on change in femur neck BMD was observed with a relative increase with prednisone use (+2.5%) compared to no concomitant prednisone use (-0.7%), (p = 0.015). CONCLUSION: In contrast to the progressive bone loss observed after conventional disease-modifying antirheumatic drug therapy, TNF blockade may result in an arrest of general bone loss. Consistent with previous observations, the data also suggest that the net effect of low-dose corticosteroids on BMD in RA may be beneficial, possibly resulting from their anti-inflammatory effects.

Sustained changes in lipid profile and macrophage migration inhibitory factor levels after anti-tumour necrosis factor therapy in rheumatoid arthritis.

BACKGROUND: Macrophage migration inhibitory factor (MIF) has recently emerged as an important cytokine possibly linking rheumatoid arthritis (RA) and atherogenesis. Because atherogenesis is accelerated in RA this study was conducted to investigate whether anti-tumour necrosis factor (TNF) therapy could lead to sustained downregulation of systemic MIF levels and improvement in lipid profiles. METHODS: Fifty RA patients with active disease (disease activity score in 28 joints (DAS28) >or=3.2), who started adalimumab therapy at 40 mg every other week, were included. At baseline, weeks 16 and 52 serum levels of MIF and lipids were assessed. In addition, the DAS28 and serum C-reactive protein (CRP) levels and erythrocyte sedimentation rate (ESR) were determined. RESULTS: After 16 weeks of adalimumab therapy, both DAS28 and MIF levels were significantly decreased (p<0.001 and p = 0.020, respectively). This was sustained up to week 52 (p<0.001 and p = 0.012, respectively). CRP levels and ESR were significantly reduced after 16 and 52 weeks of adalimumab therapy (p<0.001). High-density lipoprotein cholesterol levels increased at week 16 (p<0.001), but returned to baseline at week 52. Apolipoprotein (apo) A-I levels increased at week 16 (p<0.001) and remained stable (p = 0.005). This resulted in an improved apo B/A-I ratio. CONCLUSIONS: The results underline the sustained downregulation of MIF as a potential new mechanism by which anti-TNF therapy might reduce vascular inflammation, and as such perhaps cardiovascular morbidity in RA patients. This hypothesis is supported by an improved apo B/A-I ratio as well as reduced CRP levels in these patients.

Expression of a pathogen-response program in peripheral blood cells defines a subgroup of rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is a heterogeneous disease with unknown etiology. Here we aimed to distinguish RA subtypes based on peripheral blood (PB) gene expression profiles in comparison with a pathogen-response transcriptional program. PB was obtained from 35 RA patients and 15 healthy individuals. For expression profiling we used DNA microarrays. A combined cluster analysis of RA and control samples together with samples from a viral infection model revealed that the gene expression profile of a subgroup of RA patients (RA(A)) was reminiscent to that of poxvirus-infected macaques. Statistical analysis, followed by Gene Ontology analysis of the RA(A) patients confirmed that these patients form a distinct group, with activation of several host defense mechanisms that resemble a common host-pathogen response. Analysis of the promoter region of genes that were overexpressed in the RA(A) patients, revealed an enrichment of transcription factor binding sites for NF kappaB and interferon-activated transcription factors. Moreover, this subgroup of RA patients expressed significantly increased titers of anti-cyclic citrullinated peptide antibodies. We conclude that activation of a host-pathogen response defines a subgroup of RA patients characterized by increased autoreactivity against citrullinated proteins.

Responsiveness to anti-tumour necrosis factor alpha therapy is related to pre-treatment tissue inflammation levels in rheumatoid arthritis patients.

OBJECTIVE: The response of rheumatoid arthritis (RA) patients to treatment with neutralising antibodies to tumour necrosis factor alpha (TNFalpha) is highly variable. The underlying mechanism for therapy responsiveness is currently unknown. We therefore evaluated the relationship between baseline molecular profiles of synovial tissues from RA patients and the clinical response to treatment with infliximab. METHODS: Synovial biopsies were obtained by arthroscopy from 18 RA patients with active disease (28 joint count Disease Activity Score (DAS28) > or = 3.2) before initiation of treatment with infliximab. All patients were on stable methotrexate treatment. Clinical response at 16 weeks was defined as a reduction in DAS28 of > or = 1.2, non-response as reduction in DAS28 < 1.2. Large-scale gene expression profiling using microarrays was performed on synovial tissue samples. To identify biological processes in synovial biopsies that could discriminate between responders and non-responders, we performed pathway analysis on the expression profiles. RESULTS: A total of 12 patients responded to therapy, while 6 patients failed to fulfil the response criteria. We identified several biological processes, related to inflammation, which were up-regulated in patients who responded to therapy, compared to those who did not show clinical improvement. CONCLUSION: These results indicate that patients with a high level of tissue inflammation are more likely to benefit from anti-TNFalpha treatment.

The clinical response to infliximab in rheumatoid arthritis is in part dependent on pretreatment tumour necrosis factor alpha expression in the synovium.

OBJECTIVE: To determine whether the heterogeneous clinical response to tumour necrosis factor (TNF)alpha blocking therapy in rheumatoid arthritis (RA) can be predicted by TNFalpha expression in the synovium before initiation of treatment. METHODS: Prior to initiation of infliximab treatment, arthroscopic synovial tissue biopsies were obtained from 143 patients with active RA. At week 16, clinical response was evaluated using the 28-joint Disease Activity Score (DAS28). Immunohistochemistry was used to analyse the cell infiltrate as well as the expression of various cytokines, adhesion molecules and growth factors. Stained sections were evaluated by digital image analysis. Student t tests were used to compare responders (decrease in DAS28 > or =1.2) with non-responders (decrease in DAS28 <1.2) and multivariable regression was used to identify the independent predictors of clinical response. RESULTS: Synovial tissue analysis confirmed our hypothesis that the baseline level of TNFalpha expression is a significant predictor of response to TNFalpha blocking therapy. TNFalpha expression in the intimal lining layer and synovial sublining were significantly higher in responders than in non-responders (p = 0.047 and p = 0.008, respectively). The numbers of macrophages, macrophage subsets and T cells (all able to produce TNFalpha) were also significantly higher in responders than in non-responders. The expression of interleukin (IL)1beta, IL6, IL18, IL10, E-selectin, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) was not associated with response to anti-TNFalpha treatment. CONCLUSION: The effects of TNFalpha blockade are in part dependent on synovial TNFalpha expression and infiltration by TNFalpha producing inflammatory cells. Clinical response cannot be predicted completely, indicating involvement of other as yet unknown mechanisms.

Synovial tissue response to rituximab: mechanism of action and identification of biomarkers of response.

OBJECTIVE: To investigate the synovial tissue in patients with rheumatoid arthritis (RA) treated with rituximab and to identify possible predictors of clinical response. METHODS: A total of 24 patients with RA underwent synovial biopsy before, 4 and 16 weeks after initiation of rituximab treatment (without peri-infusional corticosteroids to prevent bias). Immunohistochemical analysis was performed and stained sections were analysed by digital image analysis. Linear regression analysis was used to identify predictors of clinical response. RESULTS: The 28-joint Disease Activity Score (DAS28) was unaltered at 4 weeks, but significantly reduced at 16 and 24 weeks. Serum levels of IgM-rheumatoid factor (RF) decreased significantly at 24 weeks and anti-citrullinated peptide antibody (ACPA) levels at 36 weeks. Peripheral blood B cells were depleted at 4 weeks and started to return at 24 weeks. Synovial B cells were significantly decreased at 4 weeks, but were not completely depleted in all patients; there was a further reduction at 16 weeks in some patients. We found a significant decrease in macrophages at 4 weeks, which was more pronounced at 16 weeks. At that timepoint, T cells were also significantly decreased. The reduction of plasma cells predicted clinical improvement at 24 weeks. CONCLUSIONS: The results support the view that B cells orchestrate local cellular infiltration. The kinetics of the serological as well as the tissue response in clinical responders are consistent with the notion that rituximab exerts its effects in part by an indirect effect on plasma cells associated with autoantibody production, which could help explain the delayed response after rituximab treatment.

Rheumatoid arthritis subtypes identified by genomic profiling of peripheral blood cells: assignment of a type I interferon signature in a subpopulation of patients.

BACKGROUND: Rheumatoid arthritis (RA) is a heterogeneous disease with unknown cause. AIM: To identify peripheral blood (PB) gene expression profiles that may distinguish RA subtypes. METHODS: Large-scale expression profiling by cDNA microarrays was performed on PB from 35 patients and 15 healthy individuals. Differential gene expression was analysed by significance analysis of microarrays (SAM), followed by gene ontology analysis of the significant genes. Gene set enrichment analysis was applied to identify pathways relevant to disease. RESULTS: A substantially raised expression of a spectrum of genes involved in immune defence was found in the PB of patients with RA compared with healthy individuals. SAM analysis revealed a highly significant elevated expression of interferon (IFN) type I regulated genes in patients with RA compared with healthy individuals, which was confirmed by gene ontology and pathway analysis, suggesting that this pathway was activated systemically in RA. A quantitative analysis revealed that increased expression of IFN-response genes was characteristic of approximately half of the patients (IFN(high) patients). Application of pathway analysis revealed that the IFN(high) group was largely different from the controls, with evidence for upregulated pathways involved in coagulation and complement cascades, and fatty acid metabolism, while the IFN(low) group was similar to the controls. CONCLUSION: The IFN type I signature defines a subgroup of patients with RA, with a distinct biomolecular phenotype, characterised by increased activity of the innate defence system, coagulation and complement cascades, and fatty acid metabolism.

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.