Search

Objectives: To study the association between the presence of antibodies against CD74 and structural damage in the sacroiliac joints and spine in patients with axial spondyloarthritis (axSpA)., Methods: Antibodies against CD74 were measured in the sera of patients with axSpA from 2 cohorts: 1. An observational cohort from Damp in Northern Germany and 2. from a clinical trial (ENRADAS), in which the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) had been evaluated by two readers blinded to the time point at baseline and two years later. The presence of antibodies against CD74 was correlated with the presence and grade of radiographic sacroiliitis in the observational cohort, and with baseline mSASSS in the ENRADAS cohort., Results: The sensitivity of IgA anti-CD74 antibodies for axSpA was 50% in the Damp cohort and 42% in ENRADAS. The presence of IgA antibodies against CD74 was associated with a higher grade of sacroiliitis (observational cohort) and a higher baseline mSASSS in the ENRADAS cohort., Conclusions: IgA antibodies against CD74 are not only markers of AS, but are associated with structural damage development in the sacroiliac joints and in the spine.

Objectives: Spondyloarthritis (SpA) is often diagnosed late in the course of the disease and improved methods for early diagnosis are required. We have tested the ability of genetic profiling to diagnose axial SpA (axSpA) as a whole group, or ankylosing spondylitis (AS) alone, in a cohort of chronic back pain patients., Methods: 282 patients were recruited from centres in the United Kingdom, Germany, Taiwan, Canada, Columbia and Turkey as part of the ASAS classification criteria for axSpA study (ASAS cohort). Subjects were classified according to the ASAS axSpA criteria, and the modified New York Criteria for AS. Patients were genotyped for ~200,000 immune-mediated disease SNPs using the Illumina Immunochip., Results: We first established the predictive accuracy of genetic data comparing 9,638 healthy controls and 4,428 AS cases from the homogenous International Genetics of AS (IGAS) Consortium Immunochip study which showed excellent predictive power (AUC=0.91). Genetic risk scores had lower predictive power (AUC=0.83) comparing ASAS cohort axSpA cases meeting the ASAS imaging criteria with IGAS controls. Comparing genetic risk scores showed moderate discriminatory capacity between IGAS AS and ASAS imaging positive cases (AUC 0.67±0.05), indicating that significant differences in genetic makeup exist between the cohorts., Conclusions: In a clinical setting of referred back pain patients suspected to have axial SpA we were unable to use genetic data to construct a predictive model better than that based on existing clinical data. Potential confounding factors include significant heterogeneity in the ASAS cohort, possibly reflecting the disease heterogeneity of axSpA, or differences between centres in ascertainment or classification performance.

Objectives: To assess the impact of non-radiographic axial spondyloarthritis (nr-axSpA) on patients and society based on real-world evidence from the Adelphi nr-axSpA Disease Specific Programme, a cross-sectional survey of rheumatologists and their patients in Germany, France, Spain, Italy and the UK., Methods: Physicians completed patient record forms for the next two patients consulting with nr-axSpA (diagnosis at the physician's judgement); patients were invited to complete a patient self-completion form. Outcomes were assessed in responders and non-responders and those treated with and without biological agents., Results: In total, 631 patients were included. Fulfilment of classification criteria varied across countries. Assessment of SpondyloArthritis international Society classification criteria were most commonly met; other criteria, including Amor and European Spondyloarthropathy Study Group criteria, were applied less frequently. Most German and UK patients had their condition classified without formal criteria. Despite being diagnosed with nr-axSpA, 13% of patients met the criteria for ankylosing spondylitis. EuroQol 5-Dimensions (3L) utility scores were lower in patients with nr-axSpA versus general population matched controls (0.776 vs. 0.884; p<0.001); non-responders to treatment had impaired activity (as measured by the Work Productivity and Activity Impairment questionnaire) of 47.4% versus 33.3% in responders (p<0.001). Clinical outcomes were consistently better in biological-treated versus -naïve patients. Average pretreatment pain levels were 6.6 and 6.2, respectively (p=0.072) but reduced to 2.5 and 4.0, respectively (p<0.001) at the time of the survey., Conclusions: nr-axSpA was associated with a significant QoL and societal burden in this study of German, French, Spanish, Italian and UK patients. Treatment with biological agents was associated with improved QoL. Considerable variability in patients' clinical characteristics were observed across the countries studied and further education, aimed at improving awareness of the condition, may be needed.

Objectives: Knowledge on the long-term effects of anti-TNF therapy in patients with ankylosing spondylitis (AS) is still limited. Our objective was to study the long-term efficacy and safety of anti-TNF therapy in AS., Methods: After having completed the first part of the EASIC trial a total of 71 patients were enrolled into this 96-week extension study. Patients were treated with the same dosages and dosing intervals of infliximab as in the EASIC core study. Efficacy was assessed by using standardised assessment tools such as BASDAI, BASFI, BASMI, patient global assessment, CRP levels and the proportion of patients without any sign of enthesitis or arthritis. Long-term safety was assessed by documenting adverse events (AE), serious adverse events (SAE) and reasons for dropping out., Results: Of the 71 patients included, 64 (90.1%) completed the trial , and 7 discontinued: one was lost to follow-up, 3 withdrew informed consent and in 3 patients therapy was stopped for different reasons: secondary loss of response, recurrent infections and basal cell carcinoma of the skin. The completers showed rather stable low scores of BASDAI (mean 2.4, median 2.52), BASFI (mean 3.1, median 2.76) and BASMI (mean 3.2, median 3) as well as patients global assessment and CRP. The vast majority of patients did not have enthesitis or arthritis. A total of 476 AE were observed, 13 of which were SAE. The majority of these were infections and most of them affected the respiratory tract. Two malignancies occurred: one basal cell carcinoma and one malignant melanoma. These were the only SAE judged to be possibly related to the study drug., Conclusions: Anti-TNF treatment with infliximab is efficacious over long periods of time in patients with AS. The observation of two skin related malignancies, including one melanoma, during the whole study period of 7 years is in line with reports from previous large AS data sets.

Remission has not been a major topic in ankylosing spondylitis (AS) in recent years but there is now increasing interest in analogy to rheumatoid arthritis (RA). RA and AS are chronic inflammatory diseases with more differences than similarities. New classification criteria for axial spondyloarthritis (axSpA) have recently added patients with so called non-radiographic axSpA to the spectrum, hereby including earlier disease stages without structural changes. Therapeutic strategies include non-steroidal anti-inflammatory agents (NSAIDs) and biologics, mainly anti-TNF agents. Both work rather well for signs and symptoms, and possibly also for structure modification. Discontinuation of anti-TNF agents has been a major topic in RA in the last 2 years. In axSpA there has been less enthusiasm because early reports have been rather discouraging. However, no prospective controlled trials have been performed. This is a clear unmet need which should be addressed in future trials.

Tumour necrosis factor-alpha inhibitors (TNF-blockers) are recommended for the treatment of predominantly axial spondyloarthritis (SpA), after failure of non-steroidal anti-inflammatory drugs (NSAIDs). TNF-blockers are very effective drugs and also show a sustained and stable long-term response in axial SpA. A few trials indicated that withdrawal of TNF-blockers in longstanding ankylosing spondylitis (AS) is not feasible. However, a recent trial in very early axial SpA suggests that reaching a state of biologic-free low disease activity may be a realistic goal in some patients. This review summarises the available data concerning withdrawal of biologic therapies in early axial SpA.

Treatment of patients suffering from active ankylosing spondylitis (AS) with TNFα blockers, has been shown to result in clinically significant improvement of signs and symptoms of the disease. Long-term extension studies with these agents have shown sustained clinical efficacy for up to 10 years in patients who continued treatment. However, only a few studies have examined whether reduction of dosage of discontinuation of anti-TNF therapy is possible. In daily clinical practice, prolongation of treatment intervals is frequently tried in patients who are in clinical remission for longer periods of time, but no data on the success of that are available. Discontinuation of treatment is usually needed in patients who want to become pregnant, and in patients with severe infections. This review summarises what is known on the topic of discontinuation of biologic treatment in patients with AS.

Objectives: To study the long-term efficacy and safety of treatment with infliximab in patients with ankylosing spondylitis (AS) in a real life setting., Methods: AS patients from 6 European countries who had finished the 2-year trial ASSERT were invited to participate in the open- label investigator-driven study EASIC. At baseline, 2 groups were formed: patients of group 1 had not been treated with infliximab after ASSERT, while those of group 2 had continuously received it. Patients of group 1 were further subdivided in group 1a: patients with a relapse and 1b: in remission. All patients of group 1a and 2 continuously received infliximab for 96 weeks, mean dose 5 mg/kg, intervals 6-8 weeks. Patients of group 1b were also treated in case of relapse., Results: A total of 103/149 patients (69%) were included in EASIC, 1.3 ± 0.9 years after the end of ASSERT: 9 in group 1a, 5 in group 1b and 89 in group 2. Most patients were male (83%), mean age 44 years. Most patients of group 2 completed the trial (86%) vs. only 5 of group 1 (33%) - mostly due to allergic reactions after readministration of infliximab. In total, there were 22 drop-outs due to 6 adverse events, 4 lack of efficacy, 3 planned pregnancy. All standard assessments indicated beneficial values over time, at week 96 significantly better than at baseline of ASSERT., Conclusions: The majority of patients were continuously and successfully treated with infliximab for 5 years, whereas discontinuation and reintroduction of therapy was less satisfactory due to the frequent occurrence of hypersensitivity reactions. Anti-TNF therapy with infliximab proved to be effective and safe on a long-term basis.

The disease modifying antirheumatic drug (DMARD) methotrexate (MTX) is widely used and well accepted for the treatment of patients with rheumatoid arthritis (RA). In ankylosing spondylitis (AS), the use of MTX is not recommended for the axial manifestations and may have some efficacy in the peripheral involvement. For this disease there is a lack of clinical trials, and most of the trials did not show efficacy on the axial symptoms of the disease. Furthermore, there is no evidence that MTX increases the effects or prevents the side effects of TNF-blockers if given in combination. In this paper the available data of MTX in AS will be discussed.

Objectives: To assess long-term safety and clinical efficacy of etanercept 25 mg subcutaneously twice weekly up to 5 years in subjects with ankylosing spondylitis (AS)., Methods: An open-label (OL), multicentre, phase 4, 156-week extension study of subjects with AS who had completed a 12-week randomised, placebo-controlled study (N=84; n=45 etanercept, n=39 placebo) followed by a 96-week OL study (n=81; n=42 etanercept/etanercept; n=39 placebo/etanercept); 59 subjects who completed the 96-week OL extension enrolled in the current OL trial and continued etanercept 25 mg BIW for an additional 156 weeks (total duration: 264 weeks, original etanercept group; 252 weeks, original placebo group). Safety was based on spontaneous reports of adverse events (AEs). Last observation carried forward was used for imputation of missing values., Results: Thirty-seven of 59 subjects (63%) completed 5 years of etanercept treatment. Serious non infectious AEs and serious infections occurred at a rate of 0.17 and 0.03 events per subject years, respectively; inflammatory bowel disease and uveitis (including iritis and iridiocyclitis) occurred at 0.01 and 0.14, respectively. No cases of tuberculosis or opportunistic infections were reported. Assessment in Ankylosing Spondylitis (ASAS) responses and improvements in Bath Ankylosing Spondylitis Functional Index and spinal mobility were sustained from week 108 through week 264., Conclusions: Etanercept was well tolerated with no new safety signals detected in subjects with AS over 5 years. Clinical efficacy and improvements in function and mobility seen during the double-blind and first OL study were sustained. These results support etanercept therapy for the long-term management of this chronic disease.

The history of classification and diagnostic criteria for rheumatoid arthritis (RA) and ankylosing spondylitis (AS) is similar and different. Important criteria sets have been published for both disease in the mid eighties, for AS in 1984 and for RA in 1987. The leading clinical symptoms, inflammatory back pain (IBP) in AS and the predominant polyarticular symmetric involvement of the hands in RA were, of course, central, and so was morning stiffness as a major clinical sign of an inflammatory disease state. In RA, there was more focus on laboratory parameters (rheumatoid factor), while this could have been the case also in AS (HLA B27) but this was not recognized at this point in time. In contrast, imaging has played a more important role in AS - especially because the sacroiliac joints are involved in the vast majority of AS patients, while in RA radiographic changes of the joints of hands and feet may contribute to the diagnosis. However, in both diseases, early structural changes visualized by conventional radiography rather have prognostic impact since these patients are much more likely to progress in comparison to others who do not have cartilage and joint damage early in the course of the disease. Further developments of criteria for AS have broadened the spectrum of AS to spondyloarthritis (SpA) and axial SpA which covers most early forms. The leading clinical symptom is chronic back pain in young adults and IBP. New criteria for RA which include more patients with early disease and anti-CCP antibodies as new markers are being developed. This is important since early treatment strategies are increasingly and successfully used to treat inflammatory diseases more efficiently.

The treatment of the two most frequent inflammatory rheumatic diseases rheumatoid arthritis (RA) and ankylosing spondylitis (AS) has some similarities but in total more differences. Thus, therapy with non-steroidal anti-inflammatory agents (NSAIDs), conventional disease modifying anti-rheumatic drugs (DMARDs) and biologic agents has a different role in the management and different efficacy in AS and RA. This implies signs and symptoms, function, and structural damage. This is in part due to the different pathogenesis: (i) while the synovium is an important target in RA it is rather the bone in AS and (ii) while the pathology in RA is rather osteodestructive to cartilage and bone presenting with erosions, it is predominantly osteoproliferative in AS as indicated by syndesmophytes and ankylosis. Biologic agents targeting tumor necrosis factor (TNF-alpha) work clinically well in both diseases but, while they clearly inhibit structural damage in RA, they do not seem to have much influence on new bone formation in AS. DMARDs are efficacious in RA but less so in AS. NSAIDs are efficacious in both RA and AS, but they are considered first line of therapy in AS while they are rather adjunctive agents in RA. In AS, NSAIDs, potentially especially coxibs, may even prevent new bone formation due to their inhibitory effect on cyclooxygenase-2.

Although both rheumatoid arthritis (RA) and ankyosing spondylitis (AS) belong to the group of chronic inflammatory rheumatic diseases, they are quite different regarding mechanisms of inflammation and repair. While RA is an erosive destructive disease with the synovium as the primary site of inflammation, the immune response in AS takes place primarily at the cartilage/bone interface, and the pathological but also the clinical picture is determined by an until not yet well defined interaction between inflammation and new bone formation. Most recently, first insights into the molecular mechanisms between inflammation and bone destruction or new bone formation could be obtained. Key molecules involved in bone homeostasis seem to differ between RA and AS patients. While the molecules sclerostin and dickkopf 1, both inhibitors of osteoblasts, are elevated in RA they are found to be rather low in AS. It can be expected that the rapidly expanding new field of osteoimmunology will help to clarify the pathogenesis of the these two diseases with possible implications for new treatment targets.

Non-steroidal anti-inflammatory drugs (NSAIDs) play different roles in the management of patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS). In RA there is minimal evidence that NSAIDs are able to alter the course of disease or prevent joint destruction and, therefore, they should mostly be used as a short-term bridging therapy. In contrast to RA, in AS NSAIDs are considered as a cornerstone of the treatment not only because of a high symptomatic efficacy, but also because they might even retard osteoproliferation and radiographic progression. Considering younger age of AS patients and lower prevalence of comorbidities, they are probably at lower risk for cardiovascular and gastrointestinal side effects of short- and long-term NSAID therapy in comparison to RA.

Objective: The aim of this study was to prospectively investigate the therapeutic efficacy and safety of infliximab therapy in NSAID-refractory AS patients, with special emphasis on impact on quality of life in daily practice., Patients and Methods: 101 AS patients with active disease (mean Bath ankylosing spondylitis activity index (BASDAI) 6.3, range 4.0-9.8) were enrolled in an open label study. Infliximab 5 mg/kg body weight was administered intravenously at week 0, 2, 6, 12, 18 and 24 followed by a final assessment at week 28. Clinical assessments included quality of life (SF-36, primary endpoint), disease activity (BASDAI), function (BASFI), metrology (BASMI), patients' and physicians' global, pain, work productivity (WPAI) and CRP., Results: Using an intention to treat (ITT) analysis, the mean SF-36 physical health component improved from 27.6 at baseline to 40.9 at study end (p<0.001), the mean SF-36 mental health component improved from 44.4 at study entry to 53.0 at final assessment (p<0.001). The Assessment of AS (ASAS-) 20 short-term improvement criteria were reached by 80.2% of patients, ASAS 40 by 60.4% and the ASAS criteria for partial remission were reached by 27.7% of patients. A BASDAI 50% improvement was found in 66.3% of patients. Comparable significant improvements were found for mean BASDAI; BASFI, BASMI, patients' and physicians' global, general pain, CRP and WPAI. 11.8% of patients stopped therapy because of side effects., Conclusions: Infliximab showed high efficacy and safety when used by non-specialised rheumatologists in daily practice.

Background and Objective: AS and other spondyloarthritides (SpA) are mostly chronic inflammatory rheumatic diseases characterised by a strong association with HLA B27. Recent data from our group have suggested that AS patients have a diminished secretion capacity of inflammatory cytokines, possibly associated with HLA B27. The aim of this study was to identify CD4+ and CD8+ T cell subsets responsible for the observed lower cytokine secretion capacity in HLA B27-positives., Methods: Highly purified (> 98%) CD4+ and CD8+ T cells of HLA B27-positive AS patients (n = 13), healthy HLA B27-positive (n = 7) and -negative controls (n = 9) were stimulated for 6h with PMA/ Ionomycin and, after fixation, stained for surface markers CD45RA and CD27 and cytokines TNFalpha, IFNgamma, IL-4 and IL-10., Results: CD27+ CD45RA- memory CD8+ T cells of HLA B27-positive subjects showed a significantly lower percentage of TNFalpha (median 71.4%) and IFNgamma production (median 69.7%) than HLA B27-negative controls (TNFalpha 85.1%; p < or = 0.027; IFNgamma 82.7%, p < or = 0.026). A similar result was also detected in CD27- CD45RA+ effector CD8+ T cells of which 43.2% produced TNFalpha and 66.3% IFNgamma in HLA B27-positive subjects, respectively, compared to 75.6% TNFalpha and 84.4% IFNgamma producing T cells in HLA B27-negatives (p < or = 0.045 and p < or = 0.062, respectively). For all CD4+ T cell subsets no significant differences between HLA B27-positive and HLA B27-negative donors were observed, regarding neither the frequency of IFNgamma, TNFalpha, IL-4 or IL-10 producers nor the coexpression of IFNgamma and IL-4 in memory subsets., Conclusions: HLA B27-positive subjects are characterized by a low proinflammatory cytokine production in CD8+ effector and memory T cell subsets. This suggests an influence of HLA B27 on cytokine production in antigen-experienced CD8+ T cells.

TNFalpha is expressed in high amounts at the site of inflammation in ankylosing spondylitis, which provided the basis to initiate treatment studies with TNF-blocking agents. We could show that the immunological effects of infliximab and etanercept differ in patients with AS, although the clinical effect was similarly good. While infliximab induced a downregulation of the production of the T-helper 1-cytokines IFNgamma and TNFalpha, etanercept treatment triggered rather an upregulation of these cytokines secreted by T cells after in vitro stimulation.

Inflammation of spinal structures is a characteristic feature of the spondyloarthritides (SpA). The term SpA covers patients with inflammatory back pain and/or peripheral arthritis who can be further categorized. Ankylosing spondylitis (AS), the prototype of the SpA, the most frequent inflammatory spinal disease in adults, usually starts in the sacroiliac joints. Pathologic spinal changes occurring in AS are spondylitis, spondylodiscitis and inflammation and ankylosis also at other sites in the axial skeleton. In the later stages of AS such changes can be well recognized by spinal x-rays. In the early disease stages it has been more difficult to analyze the exact anatomic localization of spinal inflammation to date, because conventional imaging systems have only a limited capacity to demonstrate such changes early. There is some evidence that magnetic resonance imaging (MRI) with fat saturation and contrast enhanced MRI are useful to visualize early and late inflammatory changes in the sacroiliac joints. In this paper we report that MRI is also useful to localize the site of inflammation to distinct regions of the spine in AS and other SpA.

Ankylosing spondylitis (AS), the prototype of the spondyloarthritides (SpA), is a disease subset but also a possible outcome of the SpA. Early diagnosis of sacroiliitis, the most frequent clinical symptom often accompanied by inflammatory back pain, and other inflammatory lesions of the spine such as spondylitis and spondylodiscitis, can be visualized early by magnetic resonance imaging (MRI). Chronic changes such as syndesmophytes are well detected by conventional x-rays of the spine, mostly lateral, in the lumbar spine also a.p. Active spinal inflammation can be demonstrated by MRI by using either the fat saturating STIR technique or by application of the contrast agent gadolinium-DTPA. This is especially useful in early and active disease, in young women and in children, and for the differential diagnosis of septic sacroilitis. Because of the efficacy of the novel biologic agents directed against TNFalpha such as infliximab and etanercept in SpA there is a need for spinal imaging techniques that are more sensitive than conventional x-rays. The available scoring tools are limited in their sensitivity to change. Novel approaches using MRI have been recently proposed.

For treatment of the spondylarthropathies (SpA), of which ankylosing spondylitis (AS) is the prototype, there is no effective disease modifying treatment available. In contrast to rheumatoid arthritis (RA), few studies have been performed on the treatment of patients with AS with disease modifying antirheumatic drugs, none of which have proved clearly effective in axial disease. Many patients with AS carry a heavy burden of disease and AS itself is responsible for direct and indirect socioeconomic costs. To find an effective treatment for severe ankylosing spondylitis is therefore thought to be an unmet medical need. In the last four years several pilot studies and recently a few randomised controlled trials have raised good evidence that TNFalpha blockade is very effective in AS and other SpA. Disease activity, function and quality of life improved upon treatment with TNFalpha blockers. Thus, biologicals seem to represent a major breakthrough in the treatment of AS and other SpA. Side effects similar to those observed in RA treatment occur. But there is furthermore a need for safety data for long-term treatment with biologicals over several years. In the light of the high costs and the unknown long-term side effects, a definition for patients who might be candidates for such a treatment is needed. This article gives detailed information about current experience with the new treatment options in active and severe AS with anti-TNFalpha therapy.

Spondylarthropathies (SpA) and connective tissue diseases (CTD) are clinically distinct entities which, at first glance, seem to have little in common. However, a link between SpA and CTD has recently been suggested by a study in which a higher prevalence of Sjögren's syndrome (SS) and sicca symptoms was reported in patients with ankylosing spondylitis (AS) and undifferentiated SpA (1). Another link between SpA and CTD is a possible side effect of a DMARD widely used to treat SpA: sulfasalazine (SAS). SAS was reported to induce antinuclear antibodies (ANA) and systemic lupus erythematosus (SLE)-like syndromes such as drug-induced lupus. This report describes a 54-year-old white male, HLA B27-positive AS patient with some syndesmophytes who, after 15 years of disease, developed SS with salivary gland involvement, Raynaud's syndrome and anti-Ro antibodies. Then, 20 years after the onset of AS, he became acutely ill, suffering severe myositis and myocarditis along with swollen hands and highly elevated autoantibody titers recognizing UIRNP; his condition was interpreted as mixed connective tissue disease (MCTD). The patient had been treated with SAS and azathioprine (AZA) alone several times during the last years because he had not tolerated other DMARDs. A combination of both drugs had been prescribed 3 weeks before a severe flair because of progredient high disease activity with painful peripheral arthritis of the MCP and PIP joints which, however, had not shown radiographic erosions. We describe the rare development of MCTD in an AS patient and report, for the first time, the onset of MCTD potentially triggered by sulfasalazine.

Acute neutrophilic dermatosis, also referred to as Sweet's syndrome according to the first description in 1964, occurs not only as an isolated phenomenon but also in the context of neoplastic and inflammatory diseases, occasionally including arthritides. Recently Sweet's syndrome has been reported in a small number of patients with chronic inflammatory bowel disease, mostly in advanced stages of the disease. Here, we describe the sudden outbreak of acute neutrophilic dermatosis in coincidence with the onset of severe Crohn's disease (CD) in a patient with long-standing ankylosing spondylitis (AS). This condition has not been described before and therefore Sweet's syndrome should be added to the spectrum of skin manifestations the rheumatologist has to think about in the context of the spondylarthropathies (SpA). Furthermore, this case report is of interest because the skin lesions of Sweet's syndrome are somewhat similar to psoriasis, which is a rather frequent feature of the spondylarthropathies. This article intends to clarify the clinical and histological differentiation between Sweet's syndrome, psoriatic skin lesions and erythema nodosum for the rheumatologist and stresses that these conditions must each be treated in a completely different manner.

Reactive arthritis (ReA) and rheumatoid arthritis (RA) are inflammatory joint diseases which differ in several clinical and immunological aspects. In both diseases locally activated T cells are considered important for pathogenesis. Subsets of T cells are demonstrated by staining with monoclonal antibodies recognizing isotypes of the common leukocyte antigen: CD45RA, which is considered to be a marker of native T cells, and CD45RO a marker of primed T cells; a third subset was also identified according to the staining intensity of CD45RB: CD45RBbright and CD45RBdim. The expression of these and the surface markers CD3, CD4, CD8, CD14 and CD56 was studied in synovial fluid (SF) and peripheral blood (PB) of patients with ReA (n = 11), RA (n = 10) and normal controls (n = 10) by three-colour immunocytometry. Significantly more CD45RBbright were found in the PB of patients with ReA (64.1%) and RA (63.5%) than in the SF of ReA (36.8%) and RA (40.6%) patients. However, when analyzed in relation to CD45RO, the CD45RO/CD45RBbright population was not significantly different between the SF and PB of patients with ReA (32.2% vs. 26.8%) and RA (30.6% vs. 28.1%), respectively. Among the three cellular subtypes of CD4+ lymphocytes demonstrated in this study (CD45RA/RBbright, CD45RO/CD45RBbright and CD45RO/CD45RBdim) none, in contrast to previous results of other groups, showed marked differences between ReA and RA in either of the compartments examined.