Different cytokine profiles in patients with chronic and acute reactive arthritis

I. Butrimiene, S. Jarmalaite1, J. Ranceva, A. Venalis, L. Jasiuleviciute and A. Zvirbliene2

Institute of Experimental and Clinical Medicine, Vilnius University, 1 Laboratory of Ecological Genetics, Vilnius University and 2 Laboratory of Immunology, Institute of Biotechnology, Lithuania.

Correspondence to: I. Butrimiene, Department of Rheumatology, Vilnius University Institute of Experimental and Clinical Medicine, Zygimantu 9, LT-2600, Vilnius, Lithuania. E-mail: irena.butrimiene{at}santa.lt


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Objective. Analysis of cytokine production in patients with acute and chronic reactive arthritis (AcReA/ChrReA) in order to search for new treatment possibilities.

Methods. Cytokine production by peripheral blood and synovial fluid mononuclear cells (PBMCs/SFMCs) of 28 patients with AcReA, 27 patients with ChrReA, 26 patients with rheumatoid arthritis (RA) and 31 healthy controls was analysed by enzyme-linked immunosorbent assay (ELISA) and flow-cytometry. Production of tumour necrosis factor-alpha (TNF-{alpha}), interferon-gamma (IFN-{gamma}) and interleukin (IL)-10 was measured by ELISA, while the percentages of TNF-{alpha}-, IFN-{gamma}- and IL-4-positive CD3+ cells were determined in the same groups of patients and healthy subjects using flow cytometry.

Results. Spontaneous TNF-{alpha} production observed in PBMCs of ChrReA, but not of AcReA, patients was significantly higher (P<0.001) than in healthy controls. The percentages of TNF-{alpha}-positive CD3+ blood cells in ChrReA exceeded that of RA patients and healthy controls (P<0.05 and P<0.001, respectively). Also, the percentages of IFN-{gamma}-positive CD3+ cells were significantly higher in peripheral blood and synovial fluid of ChrReA patients (P<0.05 and P<0.05, respectively) as compared with AcReA. In ChrReA spontaneous IL-10 production in PBMCs was similar to that observed in healthy controls, while in RA and AcReA the production of IL-10 was significantly increased (P<0.05 and P<0.05, respectively). IL-4 production was low in all study groups with no significant differences detected.

Conclusions. High production of TNF-{alpha} and IFN-{gamma} detected in ChrReA supports the possible use of anti-TNF-{alpha} treatment in ChrReA.

KEY WORDS: Reactive arthritis, Cytokines, TNF-{alpha}, IFN-{gamma}


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Reactive arthritis (ReA) is an acute inflammatory arthritis occurring about 1 month after the triggering infection. In most cases ReA is a self-limiting disease, lasting up to 4–5 months. Approximately 15 to 30% of patients develop chronic or recurrent arthritis or spondylitis [1]. Regardless of the fact that the pathophysiological mechanisms of the development of rheumatoid arthritis (RA) and ReA are different, the severity of chronic reactive arthritis (ChrReA) can be similar to that of RA.

Cytokines secreted by T helper (Th) cells play a key role in the pathogenesis of RA and ReA [2]. Pathogenesis of ReA is closely associated with an earlier bacterial infection mainly of the gastrointestinal or urogenital tract. It is known that cytokines of the Th1 type [interferon-gamma (IFN-{gamma}), tumour necrosis factor-alpha (TNF-{alpha}) and others] are indispensable for effective defence against bacterial infection. In ReA, impaired Th1 cytokine production may cause a failure of effective bacterial elimination at the initiation of the disease and thereby play a part in the pathogenesis of ReA [3]. Indeed, a relative lack of Th1 cytokines was detected in peripheral blood and synovium of ReA patients in several studies [4–6]. Significant associations were also observed between low TNF-{alpha} secretion and a more chronic course of ReA in HLA-B27-positive patients [6]. However, in T-cell clones derived from the synovial fluid of patients with ReA, disease-related bacterial antigens predominantly induced Th1 cytokine secretion [7–9]. Conflicting data were also reported on Th2 cytokine [interleukin (IL)-4, IL-10] production in the inflamed joints of ReA patients [4, 5, 10]. This lack of general agreement on cytokines found in ReA patients warrants further cytokine investigation in ReA.

Recently developed anti-cytokine therapy allows direct control of cytokine production in autoimmune inflammatory diseases. Clinical studies revealed significant benefits from anti-TNF-{alpha} therapy not only in RA but also in the spondyloarthropathies [11, 12]. In patients with ankylosing spondylitis anti-TNF-{alpha} therapy resulted in the rapid improvement of clinical symptoms and continued clinical benefit [13, 14]. In addition, anti-TNF-{alpha} therapy reversed abnormalities in Th cytokine pattern observed in the spondyloarthropathies [15, 16]. The first efforts to treat ReA and unclassified arthritis using anti-TNF-{alpha} therapy have recently appeared in the literature [17].

The main aim of our study was to analyse cytokine production in patients with ChrReA and compare it with acute ReA (AcReA), RA and healthy controls in order to better understand the pathophysiological mechanisms of ReA and search for new treatment possibilities. For that purpose the production of TNF-{alpha}, IFN-{gamma}, IL-10 and IL-4 was measured using enzyme-linked immunosorbent assay (ELISA) and flow cytometry in peripheral blood and synovial cells of patients and in peripheral blood of healthy controls.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Patients
Patient selection was conducted at the Rheumatology Department of Vilnius Central University Hospital with approval of the local ethics committee. ReA was diagnosed according to European Spondyloarthropathy Study Group criteria [18]. All ReA patients experienced some urogenital symptoms (dysuria, painful coitus, etc.) within a 1-month period before developing arthritis. Dermato-venerologists detected urogenital tract inflammation in 25 out of 28 (89.3%) patients with AcReA and in 23 out of 27 (85.2%) with ChrReA. AcReA was defined as ReA lasting up to 3 months and ChrReA starting from 6 months. The duration of the disease at the time of blood collection is illustrated in Table 1.


View this table:
[in this window]
[in a new window]
 
TABLE 1. Demographic and clinico-laboratory characteristics of study groups

 
Eighty-one patients (38 men, 43 women, mean age 39±2.3 yr, range 19–65 yr) and 31 healthy controls (11 men, 20 women, mean age 32±2.4 yr, range 22–64 yr) were included in this study. Of these patients, the diagnosis of AcReA was confirmed for 28 patients, ChrReA for 27 patients and RA for 26 patients. The number of tender (TJC) and swollen (SJC) joints, HLA-B27 positivity, presence of rheumatoid factor (RF) together with erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were evaluated. All patients in all patient groups received non-steroidal anti-inflammatory drugs in therapeutic doses. Eight (29.6%) patients with ChrReA, 18 (69.2%) with RA and 10 (35.7%) with AcReA received prednisolone (7.5–10 mg/day). Nineteen (70.4%) patients with ChrReA and 15 (57.7%) with RA received sulphasalazine (150–200 mg/day); four (14.8%) patients with ChrReA and five (19.2%) with RA received methotrexate (7.5–20 mg/week); two (7.4%) patients with ChrReA and two (7.7%) with RA received azathioprine (100 mg/day). The other characteristics of all study groups are presented in Table 1. Expression of cytokines TNF-{alpha}, IFN-{gamma}, IL-10 and IL-4 was analysed in peripheral blood mononuclear cells (PBMCs) by ELISA and flow cytometry. The same parameters were also measured in synovial fluid mononuclear cells (SFMCs) of 13 patients with AcReA, six patients with ChrReA and three patients with RA.

All study subjects who participated in the investigations signed a written informed consent form. This informed consent was obtained according to the Declaration of Helsinki.

Cell collection
PBMCs were separated from heparinized blood (7 ml) by a standard procedure using Ficoll density gradient centrifugation. After three washes in serum-free RPMI-1640 medium (Biochrom, Germany), the mononuclear cells were resuspended in complete growth medium (RPMI supplemented with 2 mM L-glutamine, antibiotics and 10% heat-inactivated fetal bovine serum (FBS, Biochrom, Germany) and processed for flow-cytometric analysis or cytokine assay as described below. SFMCs were isolated from the synovial fluid (7 ml) by centrifugation, washed three times with serum-free RPMI, resuspended in complete growth medium and processed for further analysis.

Cytokine assay
For cytokine assay, mononuclear cells were seeded at a density of 1 x 106 cells/ml/well into a 24-well plate and cultured in a humidified CO2 incubator for 24 h. The supernatants were collected and stored at –20°C until assay. Cytokines IL-10, TNF-{alpha} and IFN-{gamma} were analysed by a two-site ELISA. IL-10 was determined using an OptEIA hu IL-10 Set (BD PharMingen). For TNF-{alpha} detection, matched-paired monoclonal antibodies (Institute of Biotechnology, Vilnius) produced by clones NF-2 and NF-7 were used (sensitivity 100 pg/ml, standardization according to British Standard supplied by NIBSC, UK). For INF-{gamma} detection, matched-paired monoclonal antibodies (Institute of Biotechnology, Vilnius) produced by clones GIF-3 and GIF-10 were used (sensitivity 200 pg/ml, standardization according to British Standard supplied by NIBSC, UK). Analysis was performed on Nunc MaxiSorp microtitre plates. Enzymatic reaction was developed using TMB/plus substrate (Fermentas). The optical densities at 450 nm and at a correction wavelength 620 nm were measured on a microplate reader (DigiScan 400, Assys Hitech). Concentrations of cytokines were calculated using the KIM computer program. Results were expressed as median values and interquartile ranges (IQR).

Flow cytometry
For flow-cytometric analysis of intracellular cytokines, mononuclear cells were seeded at a density of 1 x 106 cells/well into a 96-multiwell plate pre-coated with anti-hu-CD3 (clone UCHT1, BD PharMingen) and incubated overnight in a humidified CO2 incubator. Cells were further incubated for 4 h with phorbol myristate acetate (PMA; Sigma, 10 ng/ml), ionomycin (Sigma, 1 mM) and the protein transport inhibitor Golgi-Plug (BD PharMingen, 3 mM). After stimulation, cells were harvested, washed once with Washing Buffer (BD PharMingen) and then permeabilized for 10 min in 4°C cold FACS permeabilizing solution (BD PharMingen). After washing, the cells were stained simultaneously with directly conjugated anti-cytokine and anti-CD3 antibodies (BD PharMingen). Cells were incubated for 20 min in the dark, washed and finally resuspended in Cell-Fix (BD PharMingen). IL-4, TNF-{alpha} and IFN-{gamma} production was determined in CD3+ cells. The threshold for cytokine positivity was set using irrelevant isotype-specific antibodies ({gamma}1/{gamma}2a, BD PharMingen). Results for cytokine-positive cells [median (IQR)] were expressed as a percentage of the respective subpopulation.

Statistical analysis
The Mann–Whitney U-test was used to compare data on immunological analysis between different study groups. The value P<0.05 was accepted as statistically significant.


    Results
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Clinical characteristics
According to clinical characteristics (Table 1) the most severe patients were in the RA group. In the RA group TJC, SJC and CRP values were statistically significantly higher (P<0.05) than in the AcReA and ChrReA groups. No significant difference in ESR values was observed in patient groups.

Spontaneous cytokine secretion by PBMCs
Spontaneous TNF-{alpha} production by PBMCs measured using ELISA was higher in all patient groups than in the healthy control group. However, statistically significant differences in TNF-{alpha} production were observed in RA and ChrReA groups when compared with healthy controls (P<0.001 and P<0.01, respectively), while for the AcReA group this difference was not statistically significant (Fig. 1). The median concentrations of TNF-{alpha} in the different groups were 70 pg/ml (IQR 0–150) in healthy controls, 142 pg/ml (IQR 30–326) in AcReA, 256 pg/ml (IQR 50–395) in ChrReA and 235 pg/ml (IQR 152–501) in RA. TNF-{alpha} production in AcReA was statistically significantly (P<0.05) lower than in RA, while TNF-{alpha} concentrations observed in the ChrReA and RA groups were similar.



View larger version (27K):
[in this window]
[in a new window]
 
FIG. 1. Spontaneous TNF-{alpha} and IL-10 production in blood of healthy controls and patients with acute and chronic reactive arthritis (AcReA/ChrReA) and rheumatoid arthritis (RA).

 
Spontaneous IFN-{gamma} production by PBMCs was low in all study groups and below detection limits in most samples.

The spontaneous production of IL-10 in all patient groups was higher than that found in the healthy controls. However, for the ChrReA group this difference was not statistically significant (Fig. 1). The median concentrations of IL-10 in the study groups were 65 pg/ml (IQR 0–322) in healthy controls, 262.5 pg/ml (IQR 103.5–412.5) in AcReA, 201 pg/ml (IQR 51–372) in ChrReA and 265 pg/ml (IQR 133–436) in RA. No statistically significant differences in cytokine production were observed between patient groups.

Cytokine-positive cells in peripheral blood
The highest percentages of TNF-{alpha}- and IFN-{gamma}-positive CD3+ cells were detected in peripheral blood of patients with ChrReA (Fig. 2). The percentages of TNF-{alpha}-positive CD3+ cells were significantly higher in peripheral blood of ChrReA patients than in healthy controls [39.5 (IQR 21.7–48.8) vs 14.5 (IQR 8.4–38.2); P<0.001] and also than in patients with RA [39.5 (IQR 21.7–48.8) vs 15.4 (IQR 10.0–37.1); P<0.05]. Meanwhile, data comparison between AcReA and ChrReA groups revealed a statistically significant difference [8.4 (IQR 4.6–17.1) vs 14.2 (IQR 9.1–29.1); P<0.05] in percentages of IFN-{gamma}-producing CD3+ blood cells (Fig. 2).



View larger version (29K):
[in this window]
[in a new window]
 
FIG. 2. Percentages of TNF-{alpha}- and IFN-{gamma}-expressing CD3+ cells in peripheral blood of patients with acute and chronic reactive arthritis (AcReA/ChrReA), rheumatoid arthritis (RA) and healthy controls.

 
The percentages of IL-4-expressing CD3+ cells were low in all study groups (from 0 to 1.2%) with no significant differences detected.

Cytokine production in synovial fluid
Cytokine production by SFMCs was also evaluated using ELISA and flow cytometry. No significant differences in spontaneous secretion of TNF-{alpha} and INF-{gamma} by SFMCs were found between different study groups by using ELISA (data not shown). The percentage of IFN-{gamma}-expressing CD3+ cells was about four times higher in the synovial fluid of patients with ChrReA than in patients with AcReA. In the synovial fluid of ChrReA patients 23.5% (IQR 12.5–41.1) of CD3+ cells were IFN-{gamma} positive, while in AcReA only 4.8% (IQR 0–14.4) of cells displayed this positivity (P<0.05) (Fig. 3).



View larger version (16K):
[in this window]
[in a new window]
 
FIG. 3. Percentages of IFN-{gamma}-expressing CD3+ cells in synovial fluid of patients with acute and chronic reactive arthritis (AcReA/ChrReA) and rheumatoid arthritis (RA).

 
Cytokine production and HLA-B27 expression
Cytokine production according to HLA-B27 status was analysed in AcReA and ChrReA groups. In the ChrReA group 10 patients were HLA-B27 positive and 17 were HLA-B27 negative. Spontaneous TNF-{alpha} and IL-10 production was up to three times higher in PBMCs from HLA-B27-negative than in HLA-B27-positive ChrReA patients. The median concentration of TNF-{alpha} in the HLA-B27-negative group was 330 pg/ml (IQR 213–501), while in the HLA-B27-positive group it was 92.5 pg/ml (IQR 20–184) (P<0.05). The median concentration of IL-10 in the HLA-B27-negative group was 244 pg/ml (IQR 103–501) and in the HLA-B27-positive group it was 74.5 pg/ml (IQR 0–238) (P<0.05). No difference in spontaneous production of these cytokines according to HLA-B27 status was observed in SFMCs of ChrReA patients. Also, no significant differences in percentages of cytokine-positive cells in peripheral blood or synovial fluid from HLA-B27-positive and HLA-B27-negative ChrReA patients were detected by flow cytometry.

In the AcReA group 12 patients were HLA-B27 positive and 16 patients were HLA-B27 negative. No significant differences in cytokine production measured by ELISA or flow cytometry were observed in AcReA according to HLA-B27 status.


    Discussion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
We analysed cytokine profiles in two groups of ReA patients matching in age and sex and being in different stages of the disease—AcReA and ChrReA. The comparison between these two groups and also with RA and healthy control groups allowed a comprehensive evaluation of changes in cytokine profiles possibly related to chronicity of ReA.

Our study revealed significant differences in cytokine profiles of ChrReA and AcReA. This was indicated by a higher production of TNF-{alpha} observed in PBMCs of patients with ChrReA than with AcReA. Also the percentage of IFN-{gamma}-expressing CD3+ cells in blood and synovial fluid was significantly higher in ChrReA than in AcReA. However, no difference in Th2 cytokine production (IL-4 and IL-10) was observed when ChrReA was compared with AcReA.

In several prospective studies patients with AcReA were evaluated for one or more years. Analysis of cytokine profiles in these studies revealed significant associations between prolonged disease duration and low TNF-{alpha} or IFN-{gamma} secretion [6, 10]. Also, correlations were detected with a more chronic course of disease and HLA-B27 antigen expression. However, the conclusions of these studies were based on analysis of small numbers of cases. Our study design allowed comparison of cytokine profiles in two ReA groups of equal numbers with different stages of the disease.

The molecular mechanisms of pathogenesis of ReA were mostly analysed in comparison with RA. Significant differences in cytokine profiles were observed in such comparisons. A relative lack of Th1 cytokines and increased production of Th2 cytokines were observed in ReA patients as compared with RA [4–6, 19, 20]. It was concluded that the relative predominance of Th2 cytokines could be responsible for ineffective antibacterial defence in ReA and thereby associated with pathogenesis of disease. Similarly, in our study, the patients with AcReA had a statistically significantly (P<0.05) lower spontaneous TNF-{alpha} level than patients with RA, while IL-10 production was similar in both groups. However, a different cytokine profile was observed in the ChrReA group. In this group the spontaneous production of IL-10 was slightly lower than in RA or AcReA, but the production of TNF-{alpha} was similar to that observed in RA. The percentages of TNF-{alpha}-positive CD3+ cells in the blood and IFN-{gamma}-positive CD3+ cells in synovial fluid of ChrReA patients were significantly higher than in RA. Our data support the idea that the relative lack of Th1 cytokines may play a significant role in pathogenesis of ReA at the acute phase of disease; however, in the chronic disease phase the repertoire of the cytokines differs and is similar to what is found in RA.

Expression of the antigen HLA-B27 is closely related to pathogenesis of ReA and other spondyloarthropathies [3, 21, 22]. A significant reduction in the expression of Th1 cytokines was detected in HLA-B27-positive patients with ankylosing spondylitis and also in healthy HLA-B27-positive controls as compared with HLA-B27-negative controls [23]. Our study revealed a similar trend in ChrReA, but not in the AcReA group. Decreased production of both TNF-{alpha} and IL-10 was detected in PBMCs from HLA-B27-positive ChrReA patients as compared with HLA-B27-negative patients. However, such an association was not supported by intracellular cytokine measurement. While genetic factors play a part in the modulation of the immune response in ReA, their influence in cytokine regulation needs to be clarified. This is supported by other authors [24].

Treatment of spondyloarthropathies, particularly ankylosing spondylitis, with monoclonal antibody to TNF-{alpha} (infliximab) is highly clinically effective [16, 25]. One study suggested short-term effectiveness and safety of anti-TNF-{alpha} therapy in ReA and unclassified arthritis [17]. Significant down-regulation of TNF-{alpha} and IFN-{gamma} production without any effect on Th2 cytokine production was observed in ankylosing spondylitis treated with infliximab [15, 16]. However, some other studies were unable to detect changes in serum pro-inflammatory cytokine level before and after anti-TNF-{alpha} treatment [24]. The data on cytokine changes during the anti-TNF-{alpha} treatment are contradictory and require further investigation in every single kind of spondyloarthropathy.

Our study revealed significant increase of TNF-{alpha} and IFN-{gamma} production in ChrReA, as compared with AcReA. This supports the possibility that anti-TNF-{alpha} treatment in ReA during the chronic phase of the disease is beneficial. Without doubt, the search for latent infection in these patients should be fully carried out and if found must be eradicated before initiation of anti-TNF-{alpha} therapy.


    Acknowledgments
 
This work was supported by a grant from the Lithuanian State Science and Studies Foundation (no K-062). Special thanks to Kastytis Beitas of Vilnius University for his work in statistical analysis of the data.

The authors have declared no conflicts of interest.


    References
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Khan MA. Update on spondyloarthropathies. Ann Intern Med 2002;136:896–907.[Abstract/Free Full Text]
  2. Gaston JS. Role of T-cells in the development of arthritis. Clin Sci 1998;95:19–31.[ISI][Medline]
  3. Sieper J. Pathogenesis of reactive arthritis. Curr Rheumatol Rep 2001;3:412–18.[Medline]
  4. Yin Z, Braun J, Neure L et al. Crucial role of interleukin-10/interleukin-12 balance in the regulation of the type 2 T helper cytokine response in reactive arthritis. Arthritis Rheum 1997;40:1788–97.[ISI][Medline]
  5. Yin Z, Siegert S, Neure L et al. The elevated ratio of interferon gamma-/interleukin-4-positive T cells found in synovial fluid and synovial membrane of rheumatoid arthritis patients can be changed by interleukin-4 but not by interleukin-10 or transforming growth factor beta. J Rheumatol 1999;38:1058–67.[CrossRef]
  6. Braun J, Yin Z, Spiller I et al. Low secretion of tumor necrosis factor alpha, but no other Th1 or Th2 cytokines, by peripheral blood mononuclear cells correlates with chronicity in reactive arthritis. Arthritis Rheum 1999;42:2039–44.[CrossRef][ISI][Medline]
  7. Lahesmaa R, Yssel H, Batsford S et al. Yersinia enterocolitica activates a T helper type 1-like T cell subset in reactive arthritis. J Immunol 1992;148:3079.[Abstract/Free Full Text]
  8. Schlaak J, Hermann E, Ringhoffer M et al. Predominance of Th1-type T cells in synovial fluid of patients with Yersinia-induced reactive arthritis. Eur J Immunol 1992;22:2771–6.[ISI][Medline]
  9. Simon AK, Seipelt E, Wu P, Wenzel B, Braun J, Sieper J. Analysis of cytokine profiles in synovial T cell clones from chlamydial reactive arthritis patients: predominance of the Th1 subset. Clin Exp Immunol 1993;94:122–6.[ISI][Medline]
  10. Bas S, Kvien TK, Buchs N, Fulpius T, Gabay C. Lower level of synovial fluid interferon-gamma in HLA-B27-positive than in HLA-B27-negative patients with Chlamydia trachomatis reactive arthritis. J Rheumatol 2003;42:461–7.[CrossRef]
  11. Van den Bosch F, Kruithof E, Beaten D et al. Randomized double-blind comparison of chimeric monoclonal antibody to tumor necrosis factor {alpha} (Infliximab) versus placebo in active spondylarthropathy. Arthritis Rheum 2002;46:755–65.[CrossRef][ISI][Medline]
  12. Braun J, Brandt J, Listing J et al. Treatment of active ankylosing spondylitis with infliximab: a randomised controlled multicentre trial. Lancet 2002;359:1187–93.[CrossRef][ISI][Medline]
  13. Braun J, Xiang J, Brandt J et al. Treatment of spondylarthropathies with antibodies against tumor necrosis factor {alpha}: first clinical and laboratory experiences. Ann Rheum Dis 2000;59(Suppl I):185–9.
  14. Brandt J, Haibel H, Sieper J, Reddig J, Braun J. Infliximab treatment of severe ankylosing spondylitis: one year follow up [letter]. Arthritis Rheum 2001;44:2937.[CrossRef][ISI][Medline]
  15. Baeten D, Van Damme N, Van den Bosch F et al. Impaired Th1 cytokine production in spondyloarthropathy is restored by anti-TNF alpha. Ann Rheum Dis 2001;60:750–5.[Abstract/Free Full Text]
  16. Zou J, Rudwaleit M, Brandt J, Thiel A, Braun J, Sieper J. Down-regulation of the non-specific and antigen-specific T cell cytokine response in ankylosing spondylitis during treatment with infliximab. Arthritis Rheum 2003;48:780–90.[CrossRef][ISI][Medline]
  17. Meador R, Hsia E, Kitumnuaypong T, Schumacher HR. TNF involvement and anti-TNF therapy of reactive and unclassified arthritis. Clin Exp Rheumatol 2002;20(Suppl 28):S130–S134.
  18. Dougados M, van der Linden S, Juhlin R et al. The European Spondylarthropathy Study Group preliminary criteria for the classification of spondylarthropathy. Arthritis Rheum 1991;34:1228–30.[ISI][Medline]
  19. Simon AK, Seipelt E, Sieper J. Divergent T-cell cytokine patterns in inflammatory arthritis. Proc Natl Acad Sci USA 1994;91:8562–6.[Abstract]
  20. Thiel A, Wu P, Lauster R, Braun J, Radbruch A, Sieper J. Analysis of the antigen-specific T cell response in reactive arthritis by flow cytometry. Arthritis Rheum 2000;43:2834–42.[CrossRef][ISI][Medline]
  21. Yu D, Kuipers JG. Role of bacteria and HLA-B27 in the pathogenesis of reactive arthritis. Rheum Dis Clin North Am 2003;29:21–36, v–vi.[ISI][Medline]
  22. Yu DT. Pathogenesis of reactive arthritis. Intern Med 1999;38:97–101.[ISI][Medline]
  23. Rudwaleit M, Siegert S, Yin Z et al. Low T cell production of TNF-alpha and IFN-gamma in ankylosing spondylitis: its reaction to HLA-B27 and influence of the TNF-308 gene polymorphism. Ann Rheum Dis 2001;60:36–42.[Abstract/Free Full Text]
  24. Keller C, Webb A, Davis J. Cytokines in the sereonegative spondyloarthropathies and their modification by TNF blockade: a brief report and literature review. Ann Rheum Dis 2003;62:1128–32.[Abstract/Free Full Text]
  25. Braun J, Brandt J, Listing J, Zink A, Alten R, Burmester G et al. Long-term efficacy and safety of infliximab in the treatment of ankylosing spondylitis: an open, observational, extension study of a three-month, randomized, placebo-controlled trial. Arthritis Rheum 2003;48:2224–33.[CrossRef][ISI][Medline]
Submitted 1 April 2004; revised version accepted 21 June 2004.



This Article
Abstract
Full Text (PDF)
All Versions of this Article:
43/10/1300    most recent
keh323v1
Alert me when this article is cited
Alert me if a correction is posted
Services
Email this article to a friend
Similar articles in this journal
Similar articles in ISI Web of Science
Similar articles in PubMed
Alert me to new issues of the journal
Add to My Personal Archive
Download to citation manager
Search for citing articles in:
ISI Web of Science (4)
Disclaimer
Request Permissions
Google Scholar
Articles by Butrimiene, I.
Articles by Zvirbliene, A.
PubMed
PubMed Citation
Articles by Butrimiene, I.
Articles by Zvirbliene, A.
Related Collections
Other Rheumatology