T cells are responsible for the enhanced synovial cellular immune response to triggering antigen in reactive arthritis

Recombinant Salmonella typhimurium outer membrane protein A is recognized by synovial fluid CD8 cells and stimulates synovial fluid mononuclear cells to produce interleukin (IL)-17/IL-23 in patients with reactive arthritis and undifferentiated spondyloarthropathy

In developing countries, one-third of patients with reactive arthritis (ReA) and undifferentiated spondyloarthropathy (uSpA) are triggered by Salmonella typhimurium. Synovial fluid mononuclear cells (SFMCs) of patients with ReA and uSpA proliferate to low molecular weight fractions (lmwf) of outer membrane proteins (Omp) of S. typhimurium. To characterize further the immunity of Omp of Salmonella, cellular immune response to two recombinant proteins of lmwf, OmpA and OmpD of S. typhimurium (rOmpA/D-sal) was assessed in 30 patients with ReA/uSpA. Using flow cytometry, 17 of 30 patients' SF CD8(+) T cells showed significant intracellular interferon (IFN)-γ to Omp crude lysate of S. typhimurium. Of these 17, 11 showed significantly more CD8(+) CD69(+) IFN-γ T cells to rOmpA-sal, whereas only four showed reactivity to rOmpD-sal. The mean stimulation index was significantly greater in rOmpA-sal than rOmpD-sal [3·0 (1·5-6·5) versus 1·5 (1·0-2·75), P < 0·005]. Similarly, using enzyme-linked immunospot (ELISPOT) in these 17 patients, the mean spots of IFN-γ-producing SFMCs were significantly greater in rOmpA-sal than rOmpD-sal [44·9 (3·5-130·7) versus 19·25 (6-41), P < 0·05]. SFMCs stimulated by rOmpA-sal produced significantly more proinflammatory cytokines than rOmpD-sal: IFN-γ [1·44 (0·39-20·42) versus 0·72 (0·048-9·15) ng/ml, P < 0·05], interleukin (IL)-17 [28·60 (6·15-510·86) versus 11·84 (6·83-252·62) pg/ml, P < 0·05], IL-23 [70·19 (15-1161·16) versus 28·25 (> 15-241·52) pg/ml, P < 0·05] and IL-6 [59·78 (2·03-273·36) versus 10·17 (0·004-190·19) ng/ml, P < 0·05]. The rOmpA-sal-specific CD8(+) T cell response correlated with duration of current synovitis (r = 0·53, P < 0·05). Thus, OmpA of S. typhimurium is a target of SF CD8(+) T cells and drives SFMC to produce increased cytokines of the IL-17/IL-23 axis which contribute to the pathogenesis of Salmonella-triggered ReA.

The turnover of synovial T cells is higher than in T cells in the peripheral blood in persistent oligoarticular juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) summarizes a group of inflammatory diseases of childhood. The etiology remains still unclear. In JIA, T cells have been demonstrated to play key roles in the pathogenesis. T-cell proliferation in JIA may be different in the peripheral blood (PB) and the synovial fluid (SF). The aim of this study is to demonstrate the turnover of T cells in the PB and SF of patients with persistent oligoarticular JIA (oJIA) compared to controls. Matched pairs of samples were investigated derived from PB and SF of nine patients with persistent oJIA. The cells from PB and SF were determined by flow cytometry. The majority of the PBMC and IAMC were in phase G0/G1, with fewer than 1% in S phase. In the SF, the percentage of cells in the S phase are higher than in the PB. The percentage of cells in the S phase in SF are equal to the result in the control group. In conclusion, the turnover of synovial T cells in persistent oJIA is higher than in the PB.

Low molecular weight proteins of outer membrane of Salmonella typhimurium are immunogenic in Salmonella induced reactive arthritis revealed by proteomics

In patients with reactive arthritis (ReA)/undifferentiated spondyloarthropathy (uSpA), synovial fluid mononuclear cells (SFMC) show proliferation to bacterial antigens that trigger ReA, i.e. Chlamydia, Yersinia, Campylobactor, Shigella and Salmonella species. We have shown previously that SFMC proliferate significantly to outer membrane proteins of S typhimurium in Salmonella induced ReA. In the present study we characterized the immunoreactive fractions of outer membrane protein (Omp) of S typhimurium in Salmonella induced ReA. Omp of Salmonella was isolated and fractionated by continuous elution sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) using Prep-Cell into eight Omp fractions based on molecular weight. Twenty-three patients with ReA were screened for the bacterial trigger using the SFMC proliferative response to crude lysates of Y enterocolitica, S flexneri, C jejuni and S typhimurium using thymidine uptake assay. SFMC from patients with salmonella induced ReA were tested against eight fractions. Seven of 23 patients with ReA had S typhimurium-induced ReA. Of these seven patients, five patients SFMC had a significant stimulation index (SI) against < 22, 22-26, 25-35 and 28-40 kDa fractions of Omp. These fractions were analysed by SDS-PAGE and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, which revealed 10 proteins. These proteins were 37 kDa OmpA, 33 kDa TsX, 28 kDa putative Omp, 28 kDa Vac J, 39 kDa OmpD, 18 kDa OmpX, 23 kDa OmpW, 43 kDa OmpS1 and 19 kDa peptidoglycan-associated lipoprotein. In conclusion, for the first time we have identified some low molecular weight proteins in the Omps of Salmonella which are T cells immunoreactive in patients with salmonella induced ReA/uSpA.

Immunogénétique de la spondylarthrite ankylosante

BACKGROUND

Ankylosing spondylitis (AS) is an inflammatory rheumatic disease with axial involvement but its physiopathology remains unexplained. This latter combines genetic and environmental factors as well as an abnormal immune response.

CURRENT TOPICS AND IMPORTANT RESULT

This review addresses the different aspects of AS immunogenetic. A genetic background in AS is suggested by familial cases, concordance rate in twins and transmission of the disease in siblings. Ankylosing spondylitis is strongly associated with the expression of the HLA Class I antigen, B27, but also with other genes not yet identified since currently, only chromosomic area have been linked to AS. Studies of candidate genes or genome screening allow to determine these chromosomic regions. HLA-B27 is directly associated with the disease physiopathology as suggested by animal models of rats transgenic for human HLA-B27 and beta2 microglobulin. This HLA molecule have original biological properties, in particular a slow heavy chain folding and the formation of heavy chain homodimers without light chain. However, HLA B27 is a functional molecule and assumes its property of presenting peptide of 9 amino acids to CD8+ T cells. Interaction modelling studies between HLA B27 and peptides have identified peptide and peptide groove amino acid sequences, with the identification of critical positions on the HLA B27 molecule for the peptide interaction. Original biochemical properties of HLA-B27 include diminished bacterial antigen response and CD4+ T lymphocyte stimulation. Innate immunity is also of interest in AS, as suggested by the presence of macrophage and polymorphonuclear neutrophils in AS synovitis, as well as the contribution of Toll-like receptors.

FUTURE PROSPECTS AND PROJECTS

Thus in AS, the inflammatory process and then the clinical consequences may be explained by the involvement of HLA-B27, a bacterial antigen presentation, an abnormal immune response and the contribution of innate immunity, T CD4+ but also T CD8+ cells. The original molecular structures of HLA-B27 are certainly involved in this complex physiopathology, but their direct influence on the disease remains to be precised.

Spondyloarthropathy: disease at the crossroads of immunity

Up until recently, the prevailing paradigm relating to spondyloarthropathy (SpA) pathogenesis was that they were human leukocyte antigen (HLA)-associated, T-cell-driven autoimmune diseases. This view is now being questioned. Careful studies of well-characterised cohorts of patients with SpA, including detailed analysis of involved tissue, together with clinical trials of targeted treatments, in particular anti-tumour necrosis factor (TNF) therapies, have contributed enormously to both interest in and understanding of disease pathogenesis. In this chapter, our current knowledge and understanding of the relative contributions of the components of the innate and adaptive arms of the immune response to SpA pathogenesis is reviewed. It is clear that both arms of the immune response are involved and inter-dependent in SpA. With continued emphasis on discovery research, including detailed analysis of novel therapeutic interventions, significant additional breakthroughs in SpA are likely to be forthcoming.

Three month treatment of reactive arthritis with azithromycin: a EULAR double blind, placebo controlled study

OBJECTIVE

To determine the efficacy of weekly treatment with oral azithromycin for 13 weeks on the severity and resolution of reactive arthritis (ReA).

METHODS

186 patients from 12 countries were enrolled in a randomised, double blind, placebo controlled trial. Inclusion criteria were inflammatory arthritis of < or =6 swollen joints, and disease duration of < or =2 months. All patients received a single azithromycin dose (1 g) as conventional treatment for possible Chlamydia infection, and were then randomly allocated to receive weekly azithromycin or placebo. Clinical assessments were made at 4 week intervals for 24 weeks.

RESULTS

152 patients were analysable (34 failed entry criteria), with a mean (SD) age of 33.8 (9.4) and duration of symptoms 30.7 (17.5) days. Mean C reactive protein (CRP) was 48 mg/l, and approximately 50% of those typed were HLA-B27+, suggesting that the inclusion criteria successfully recruited patients with acute ReA. Treatment and placebo groups were well matched for baseline characteristics. There were no statistical differences for changes in any end point (swollen and tender joint count, joint pain, back pain, heel pain, physician and patient global assessments, and CRP) between the active treatment and placebo groups, analysed on an intention to treat basis or according to protocol completion. The time to resolution of arthritis and other symptoms or signs by life table analyses was also not significantly different. Adverse events were generally mild, but were more commonly reported in the azithromycin group.

CONCLUSIONS

This large trial has demonstrated that prolonged treatment with azithromycin is ineffective in ReA.

Investigation of infectious agents associated with arthritis by reverse transcription PCR of bacterial rRNA

In reactive and postinfectious arthritis the joints are generally sterile but the presence of bacterial antigens and nucleic acids has been reported. To investigate whether organisms traffic to affected joints in these conditions, we performed reverse transcription PCR using universal primers to amplify any bacterial 16S rRNA sequences present in synovial fluid. Bacterial sequences were detected in most cases, even after treatment of the synovial fluid with DNase, implying the presence of bacterial RNA and therefore of transcriptionally active bacteria. Analysis of a large number of sequences revealed that, as reported in rheumatoid arthritis, most were derived from gut and skin commensals. Organisms known to have triggered arthritis in each case were not found by sequencing the products obtained using universal primers, but could in some cases be shown to be present by amplifying with species specific primers. This was the case for Yersinia pseudotuberculosis and Chlamydia trachomatis. However, in arthritis thought to be related to Campylobacter infection the sequences obtained were not from Campylobacter jejuni or C. coli, but from other Campylobacter spp. that are not known to be associated with reactive arthritis and are probably present as commensals in the gut. We conclude that although rRNA from reactive arthritis associated organisms can be detected in affected joints, bacterial RNA from many other bacteria is also present, as was previously noted in studies of other forms of inflammatory arthropathy.

An association between the acute phase response and patterns of antigen induced T cell proliferation in juvenile idiopathic arthritis

The aim of this research was to determine whether all memory T cells have the same propensity to migrate to the joint in patients with juvenile idiopathic arthritis. Paired synovial fluid and peripheral blood mononuclear cell proliferative responses to a panel of antigens were measured and the results correlated with a detailed set of laboratory and clinical data from 39 patients with juvenile idiopathic arthritis. Two distinct patterns of proliferative response were found in the majority of patients: a diverse pattern, in which synovial fluid responses were greater than peripheral blood responses for all antigens tested; and a restricted pattern, in which peripheral blood responses to some antigens were more vigorous than those in the synovial fluid compartment. The diverse pattern was generally found in patients with a high acute phase response, whereas patients without elevated acute phase proteins were more likely to demonstrate a restricted pattern. We propose that an association between the synovial fluid T cell repertoire and the acute phase response suggests that proinflammatory cytokines may influence recruitment of memory T cells to an inflammatory site, independent of their antigen specificity. Additionally, increased responses to enteric bacteria and the presence of alphaEbeta7 T cells in synovial fluid may reflect accumulation of gut associated T cells in the synovial compartment, even in the absence of an elevated acute phase response. This is the first report of an association between the acute phase response and the T cell population recruited to an inflammatory site.

Juvenile onset spondyloarthropathies: therapeutic aspects

Juvenile onset spondyloarthropathy (SpA) is a term that refers to a group of human leucocyte antigen (HLA)-B27 associated inflammatory disorders affecting children under the age of 16 years, producing a continuum of clinical symptoms through adulthood. This disease is characterised by enthesopathy and arthropathy affecting the joints of the lower extremities and seronegativity for IgM rheumatoid factor and antinuclear antibodies. Children usually present with undifferentiated SpA and progress to differentiated forms over time. Except for the prevalence of some clinical features at onset, the pathogenic and clinical aspects of juvenile onset SpAs resemble those of the adult disease. Thus application of the same or similar therapeutic measures for both juvenile and adult onset SpAs seems logical. Current treatments for juvenile onset SpA provide symptomatic improvement, but do not alter disease progression. The increased expression of tumour necrosis factor alpha (TNFalpha) in synovial tissue of patients with adult and juvenile onset SpA and its correlation with infiltration of inflammatory mediators into the synovia suggest a significant pathogenic role of this cytokine. Clinical trials of anti-TNFalpha antibody (infliximab) therapy in patients with adult onset SpA have demonstrated significant clinical improvement in inflammatory pain, function, disease activity, and quality of life in correlation with histological and immunohistochemical evidence of modulation of synovial inflammatory processes. These promising findings suggest that anti-TNFalpha therapy may confer similar benefits in patients with juvenile onset SpA.

T-cell activation without proliferation in juvenile idiopathic arthritis

A study was done to determine if the differentiation and activation phenotype of T cells in synovial fluid (SF) from patients with juvenile idiopathic arthritis (JIA) is associated with T-cell proliferation in situ. Mononuclear cells were isolated from 44 paired samples of peripheral blood and SF. Differentiation and activation markers were determined on CD4 and CD8 T cells by flow cytometry. Cell-cycle analysis was performed by propidium iodide staining, and surface-marker expression was also assessed after culture of the T cells under conditions similar to those found in the synovial compartment. The majority of the T cells in the SF were CD45RO+CD45RBdull. There was greater expression of the activation markers CD69, HLA-DR, CD25 and CD71 on T cells from SF than on those from peripheral blood. Actively dividing cells accounted for less than 1% of the total T-cell population in SF. The presence or absence of IL-16 in T-cell cultures with SF or in a hypoxic environment did not affect the expression of markers of T-cell activation. T cells from the SF of patients with JIA were highly differentiated and expressed early and late markers of activation with little evidence of in situ proliferation. This observation refines and extends previous reports of the SF T-cell phenotype in JIA and may have important implications for our understanding of chronic inflammation.

Analysis of the antigen-specific T cell response in reactive arthritis by flow cytometry

OBJECTIVE

In reactive arthritis (ReA) a bacteria-specific T cell response to the triggering microbe is detected in synovial fluid (SF), and an impaired Th1 cytokine response has been described. The recent identification of immunodominant bacterial proteins/peptides and new technologies make a more detailed analysis of the immune response possible. The aim of the present study was to use these new techniques to determine the antigen-specific T cell frequency and the cytokine secretion pattern on stimulation with bacteria-derived recombinant proteins in the peripheral blood (PB) and SF from patients with ReA.

METHODS

In 3 patients with Chlamydia-induced ReA and 2 patients with Yersinia-induced ReA, the SF T cell response was investigated after stimulation with the Chlamydia-derived proteins major outer membrane protein (MOMP) and heat-shock protein 60 (Hsp60) and the Yersinia-derived proteins 19-kd protein and Hsp60. In 3 of these patients, the PB T cell response was investigated in parallel. T cells were stimulated in whole blood or whole SF with antigen plus anti-CD28 for 6 hours, brefeldin A was added after 2 hours, and cells were fixed and stained with antibodies against the surface markers CD4 and CD69 and against the cytokines interferon-gamma (IFNgamma), tumor necrosis factor alpha, interleukin-10 (IL-10), and IL-4. Positive cells were quantified by flow cytometry.

RESULTS

In the 3 patients with Chlamydia-induced ReA, the antigen-specific T cell frequency (percentage of IFNgamma CD69 double-positive CD4+ T cells) in response to MOMP (mean +/- SD 1.2 +/- 1.38%) and to Hsp60 (1.21 +/- 1.45%) in SF was about the same. In the 2 patients with Yersinia-induced ReA, the mean +/- SD frequency was 0.66 +/- 0.36% in response to the Hsp60 and 03% +/- 0.22 in response to the 19-kd protein. In the 3 patients whose PB was evaluated, the corresponding T cell response was > or =10 times lower. In 2 patients with Chlamydia-induced ReA, antigen-specific IL-10-positive CD4+ T cells were detected in 0.10-0.23% of the CD4+ T cell subpopulation.

CONCLUSION

The frequency of antigen-specific T cells to Chlamydia- and Yersinia-derived antigens in the SF of ReA patients is between 1:200 and 1:50. Both the chlamydial Hsp60 and MOMP are dominant T cell antigens in Chlamydia-induced ReA. In patients with Chlamydia-induced ReA, we detected antigen-specific IL-10 secretion, which might mediate an inhibition of effective bacterial clearance.

Two forms of reactive arthritis?

Inflammatory arthritides developing after a distant infection have so far been called reactive or postinfectious, quite often depending on the microbial trigger and/or HLA-B27 status of the patient. For clarity, it is proposed that they all should be called reactive arthritis, which, according to the trigger, occurs as an HLA-B27 associated or non-associated form. In addition to the causative agents and HLA-B27, these two categories are also distinguished by other characteristics. Most important, HLA-B27 associated arthritis may occur identical to the Reiter's syndrome with accompanying ureteritis and/or conjunctivitis, whereas in the B27 non-associated form this has not been clearly described. Likewise, only the B27 associated form belongs to the group of spondyloarthropathies.

Cytokines and the immunopathology of the spondyloarthropathies

In contrast to rheumatoid arthritis (RA), the triggering antigens are known in reactive arthritis (ReA) and Lyme arthritis. Thus, in these arthritides the antigen-specific T-cell response can be investigated in much detail and lessons possibly learned for other spondyloarthropathies (SpA) such as ankylosing spondylitis (AS) where T cells may well also play an important role in the pathogenesis. This article focusses on the immunopathology of the SpA, ReA, and AS with special reference to T cells and cytokines.

Bowel inflammation and the spondyloarthropathies

The concept of spondyloarthropathies gathers together a group of chronic diseases in which not only the locomotor system is involved but also other organs, especially the gastrointestinal tract. In humans, ileocolonoscopic studies demonstrated the presence of inflammatory gut lesions in all the diseases in the spondyloarthropathy group; their presence varied in the different diseases between 20% and 70%. The inflammation could be related to specific disease features in the spondyloarthropathies. Further research supports the hypothesis of subclinical inflammatory bowel disease in some patients with spondyloarthropathy, in which the locomotor inflammation was the only clinical manifestation. The link between gut inflammation and arthropathy has also been demonstrated in animal models, notably the human leukocyte antigen B27 transgenic rats. The temporal relationship between activity and severity of colonic involvement and flares of peripheral arthritis directs treatment of choice. For all forms of enterogenic arthropathies, nonsteroidal anti-inflammatory drugs remain the acute treatment form. Caution is in order, however, because of their possible harmful effects on intestinal integrity, permeability, and even on gut inflammation.

Analysis of T cell subsets present in the peripheral blood and synovial fluid of reactive arthritis patients

OBJECTIVE

Reactive arthritis (ReA), a HLA-B27 associated arthropathy, develops in susceptible people after infection with certain bacteria. T cells have been implicated in the pathogenesis of the arthritis but which of the different subsets is involved is still debated. This study has further elucidated the role of the CD4+ and CD8+ T cells by examining the expression of various surface markers associated with activation.

METHODS

Three colour flow cytometry was used to examine the phenotype of the T cells within the synovial fluid (SF) and peripheral blood (PB) of ReA patients.

RESULTS

ReA SF, compared with paired PB, contained a higher percentage of CD69+, CD25+, and HLA-DR+ CD3+ T cells. The majority of SF T cells also expressed the putative memory marker CD45RO. Within the T cell subsets, CD25 was expressed primarily on the CD4+ T cells; however more CD8+ T cells were HLA-DR+.

CONCLUSION

The results show that both CD4+ and CD8+ T cell populations demonstrate evidence of recent activation. Whether these cells are involved in inducing inflammation, regulating the inflammation, or have become active as a result of migration through the endothelium, remains to be determined by functional studies.

Juvenile-onset spondyloarthropathies

This article discusses the clinical spectrum and characteristics of juvenile-onset spondyloarthropathies and includes a review of the demographic, clinical, radiographic (and other imaging techniques), and laboratory data of conditions, syndromes, and diseases making up this group. The pathogenic role of several factors in the context of adult-onset patients, but also in regards to studies already performed in juvenile-onset patients, is discussed.

T cell receptor alpha-chain and beta-chain junctional region homology in clonal CD3+, CD8+ T lymphocyte expansions in Felty's syndrome

OBJECTIVE

Up to 42% of patients with Felty's syndrome (FS) have peripheral blood expansions of CD3+,CD8+ large granular lymphocytes (LGLs). The aim of this study was to determine whether the T cell receptor (TCR) alpha- and beta-chain sequences of these expansions from different patients have features in common that would support the hypothesis of an antigen-driven process.

METHODS

Extraction of RNA from peripheral blood lymphocytes followed by synthesis of complementary DNA, inverse polymerase chain reaction (PCR) with TCR-specific primers, bacteriophage transformation, and sequencing of PCR products.

RESULTS

Structural analysis of TCR beta-chain usage in such patients demonstrated a junctional region motif comprising the amino acids -LG- or -RG- in 7 of 14 clonal sequences and the motif -GXG- in 8 of 14. A biased alpha-chain junctional region usage of a hydrophobic and/or basic amino acid at position 2 was seen in 5 of 8 expanded sequences. These features differed significantly from control sequences.

CONCLUSION

Given current models of TCR-peptide-major histocompatibility complex interaction, these observations are consistent with an antigen-driven, rather than a superantigen-driven, process in at least a subgroup of patients with FS.

Aetiological agents and immune mechanisms in enterogenic reactive arthritis

Reactive arthritis is triggered by an infection, either of the genitourinary or gastrointestinal tracts; the common triggering bacteria in enteric ReA include salmonella, shigella, yersinia, and campylobacter. It is still not clear how such different bacteria can lead to a similar clinical picture and have a similar association with the MHC class I antigen HLA-B27. Common both to enterogenic and urogenic bacteria is the type of peripheral joint involvement. However, this is not so different from other bacteria-associated arthritides and is probably the consequence of bacteria persistent inside the joint. What is unique to these bacteria is the HLA-B27-association and the nearly exclusively B27-linked clinical manifestations as sacroiliitis and iritis. Shigella-induced ReA has the highest B27-association while in salmonella- and chlamydia-induced ReA a lower association can be found. Mucosal entry of enterogenic bacteria give easy access to macrophages which might be important for the transport into the joint. Although bacteria-specific antibodies are of diagnostic value, the humoral immune response does not explain the immunopathogenesis and MHC-association of this disease. Bacteria-specific T-cells have been constantly found in the synovial fluid from ReA patients and have been further analysed. The identification of immunodominant antigens of these bacteria is of great importance to understand the pathogenesis. Although an antigen shared by all bacteria has not been identified until now progress is being made in this field. We have also to consider the possibility that these bacteria are not only driving the immune response themselves but rather work as a trigger for autoimmunity.

Heterogeneity of rearranged T cell receptor V alpha and V beta gene transcripts in synovial fluid T cells of HLA-B27 positive reactive arthritis patients

To analyze the T cell receptor (TCR) V-alpha/beta gene usage by synovial fluid (SF) and peripheral blood (PB) T cells of HLA-B27+ reactive arthritis (ReA) patients. The TCR V-alpha/beta gene usage was determined by the polymerase chain reaction on freshly isolated SF and PB mononuclear cells (MNC) of five HLA-B27+ ReA patients. A total of 30 TCR V alpha and 23 V beta (sub)family specific primers in combination with a C alpha or C beta specific primer, respectively, were used. In five patients most of the TCR V alpha and V beta gene segments expressed by PB T cells were also detected in the paired SF samples. Although one patient showed an increased expression of TCR V alpha2 in SF when compared to PB, the SF samples showed a heterogeneous TCR V-gene repertoire similar to PB. Although this study was limited to a small group of patients, the apparent lack of a restricted TCR V-gene repertoire in SF does not support the involvement of a single or limited number of T cell subsets in the disease process of HLA-B27+ ReA patients.

Reactive arthritis-associated bacteria can stimulate lymphocyte proliferation in non-exposed individuals and newborns

In reactive arthritis (ReA) a specific T cell response to the triggering bacterial antigen is present in the synovial fluid, while in paired peripheral blood T cells the response is markedly reduced. The proliferative response to ReA-associated bacteria in the peripheral blood of ReA patients was compared with that seen in the blood of healthy adults, who denied exposure to these microbes, and in the umbilical cord blood of newborns, who have clearly not been exposed to bacterial antigen. Peripheral blood mononuclear cells (PBMC) from non-exposed adults and those from umbilical cord blood proliferated to ReA-associated bacteria, whilst little response was seen in ReA PBMC. The response was MHC class II-restricted, required processing of the bacterial antigen, was seen in both CD45RO+ and CD45RA+ subsets, and was not oligoclonal. These T cell responses are similar to those previously demonstrated in non-exposed individuals to malaria, leishmania and trypanosoma antigen, and may reflect the existence of 'natural' T cell immunity to ReA-associated bacteria. The lack of such responses in ReA peripheral blood may suggest that such 'natural' responses may restrict the dissemination or progression of infection.

Innovative treatment approaches for rheumatoid arthritis. T-cell regulation

There is considerable evidence to implicate T cells in the pathogenesis of rheumatoid arthritis (RA). They initiate and sustain inflammation and therefore are attractive targets for immunotherapy. Several strategies targeting T cells have been tried in RA. The use of monoclonal antibodies to deplete T cells have been used extensively but with little success. Studies have shown that T cell depleting antibodies produce profound peripheral blood lymphopenia but they are less effective in depleting lymphocytes in the joint. Since clinical efficacy is likely to depend on depleting almost all synovial lymphocytes, high doses of monoclonal antibodies would have to be given. However, the invariably severe peripheral blood lymphopenia induced by such a regimen is likely to result in profound immunosuppression. Therefore, this strategy has been abandoned and recent attempts have been made to induce tolerance in RA. In animal models of RA, treatment with high dose non-depleting anti-CD4 monoclonal antibody protects them from arthritis induced by injection of streptococcal cell wall. In addition, it leads to a state of anergy which protects the animals from arthritis induction without further treatment with anti-CD4 monoclonal antibody. This is currently being used in clinical trials of RA. Other tolerance inducing treatment strategies include T cell or T cell receptor vaccination and oral tolerance. The former is particularly difficult since the rheumatoid arthritogenic antigen and the pathogenic T cell remain unknown. The latter has shown promise in placebo controlled trials although the ideal dosage remains unknown. The mechanism of action of oral tolerance involves either immunosuppressive T cell cytokines, T cell anergy or depletion.

Pathogenesis of spondylarthropathies. Persistent bacterial antigen, autoimmunity, or both?

We have discussed partially mutually exclusive, partially overlapping models for the pathogenesis of the spondylarthropathies. Not all possibilities have been presented here; others are discussed elsewhere (77, 78). Furthermore, we have not addressed the issue of B27-negative spondylarthropathy. However, in our opinion, the key to understanding the pathogenesis of the spondylarthropathies lies in the interaction between the class I MHC molecule HLA-B27 and the T cell response. Although a T cell response driven by persisting bacterial antigen is still an attractive hypothesis, it does not explain all the known aspects of spondylarthropathy pathogenesis. The possibility of autoimmunity triggered by bacterial infection needs also to be considered, especially the new idea of HLA-B27-derived peptides presented by class II MHC molecules. The predominant involvement of joints is not easily explained in the case of autoimmunity. Cross-reactivity to joint-specific structures such as type II collagen (79) and/or bacteria inside the joint at the beginning of the immune response, with induction of local autoimmunity, might be involved. Most of the issues raised here could be tested by experiment, and we can expect to learn soon whether any of these models will explain the pathogenesis, or if we have to look further. The PCR technique will facilitate the search for bacteria not only in peripheral joints, but also now in sacroiliac biopsy samples from patients with AS and other spondylarthropathies. A prospective study on ReA in an endemic area should teach us more about predisposing factors (for example for Shigella-induced enteritis, which occurs in many parts of the world outside Europe and the US) (80).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of immunohistologic and in situ hybridization techniques in the examination of sacroiliac joint biopsy specimens from patients with ankylosing spondylitis

OBJECTIVE

To investigate mechanisms involved in inflammation and new bone formation in the sacroiliac (SI) joints of patients with ankylosing spondylitis (AS).

PATIENTS AND METHODS

Computed tomography-assisted biopsy of the SI joint was performed in 5 patients with AS with a mean disease duration of 4.5 years and radiographic stage 2-3 disease. Immunohistologic studies were performed with the alkaline phosphatase-anti-alkaline phosphatase technique, and cytokine messenger RNA (mRNA) was detected by in situ hybridization.

RESULTS

Dense cellular infiltrates with varying amounts of CD3+ cells (mean +/- SD 53.3 +/- 24.1%), CD4+ cells (29.7 +/- 17.6%), CD8+ cells (15.8 +/- 11.4%), CD14+ cells (23.6 +/- 16.9%), CD45RO+ cells (48.4 +/- 23.6%), and CD45RA+ cells (4.5 +/- 2.9%) were found in the synovial portion of the SI joints of all 5 patients. In these infiltrates a high amount of tumor necrosis factor alpha (TNF alpha) mRNA and, near the site of new bone formation, a lower amount of transforming growth factor beta (TGF beta) mRNA, were detected, while no message for interleukin-1 was found in the 3 patients examined by this technique.

CONCLUSION

The presence of T cells and macrophages was demonstrated in cellular infiltrates in the SI joints of 5 patients with active AS. The finding of abundant TNF alpha message in these joints could have implications regarding potential immunotherapeutic approaches to this disease. TGF beta might be involved in new bone formation in AS.

PPD and hsp65 induced monoarthritis initiates spontaneous recurrent flares in Lewis rats

OBJECTIVES

To investigate the time course of a monoarthritis induced with the purified protein derivative of tuberculin (PPD) or a recombinant 65 kDa heat shock protein (rhsp65) in two different strains of sensitised rats.

METHODS

Wistar and Lewis rats, sensitised with heat killed Mycobacterium tuberculosis in oil, were challenged intraarticularly with PPD or rhsp65 and monitored for six weeks. Inflammation was assessed by joint swelling, histology, and radiographic studies.

RESULTS

Sensitised Lewis rats injected with PPD or rhsp65 showed a chronic response with recurrent spontaneous flares, while Wistar rats showed one inflammatory episode.

CONCLUSIONS

The Wistar strain response to PPD resembles a transient reactive arthritis, while the response of the Lewis strain mimics the relapsing nature of rheumatoid synovitis, providing an interesting model to determine dominant immunopathogenic mechanisms.

The evolutionarily conserved ribosomal protein L23 and the cationic urease beta-subunit of Yersinia enterocolitica O:3 belong to the immunodominant antigens in Yersinia-triggered reactive arthritis: implications for autoimmunity

BACKGROUND

Reactive arthritis (ReA) is a T cell mediated inflammatory process. The immune response is primarily directed against a triggering organism, although autoimmunity has been invoked in long-lasting, antibiotic-resistant disease. Although a variety of different species are known to trigger Reactive arthritis, the clinical manifestations are strikingly similar as well as closely associated to the HLA-B27 (70%).

MATERIALS AND METHODS

Various antigenic fractions and single antigens of Yersinia enterocolitica were prepared, and their immunological activity was assessed by proliferation of synovial fluid mononuclear cells from 10 Reactive arthritis patients. The gene encoding one hitherto unknown antigen has been sequenced. Nonapeptides deduced from sequences of the target antigens were tested in an assembly assay.

RESULTS

Two immunodominant proteins of Yersinia enterocolitica were found, one being the urease beta-subunit and the other the 50 S ribosomal protein L23. The latter has been sequenced and belongs to the evolutionarily conserved ribosomal proteins with homology to procaryotes and eucaryotes. One nonapeptide derived from the urease beta-subunit was identified as a possible epitope for HLA-B27-restricted cytotoxic T cells by its high affinity. This epitope is also highly conserved.

CONCLUSION

Sharing of conserved immunodominant proteins between different disease triggering microorganisms could provide an explanation of the shared clinical picture in Reactive arthritis. Moreover, autoimmunity in Reactive arthritis might be mediated by antigen mimicry between evolutionarily conserved epitopes of ribosomal proteins and their host analogs.

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

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

Role of bacteria-specific T cells in the immunopathogenesis of reactive arthritis

Reactive arthritis is a usually self-limited sterile inflammation of joints that follows certain bacterial gastrointestinal or urogenital infections. The immunopathogenesis involves CD4+ T cells, which mediate an antigen-specific TH1 response to bacterial constituents within the joint. Properties of the arthritogenic bacteria and the physicochemical characteristics of the bacterial antigens may contribute to the development of reactive arthritis.

Cellular immune mechanisms in rheumatoid arthritis and other inflammatory arthritides

Advances in molecular genetics, cellular immunology and microbiology have offered promise in unravelling the aetiopathogenesis of inflammatory arthritides such as rheumatoid arthritis and reactive arthritis. Such insights are challenging the orthodox view that these diseases are primarily autoimmune in nature, and should lead to exciting and novel therapeutic approaches.

Analysis of cytokine profiles in synovial T cell clones from chlamydial reactive arthritis patients: predominance of the Th1 subset

Subpopulations of human T cells (Th0, Th1 and Th2) can be distinguished by their cytokine-secretion pattern. Evidence is increasing from other studies that the outcome of a human disease may depend on the subpopulation of T cells that predominates at the site of inflammation. Reactive arthritis serves as a useful model of chronic inflammatory diseases, because the triggering antigen can be identified. Using this triggering antigen we raised 33 T cell clones reactive with Chlamydia trachomatis and 25 T cell clones that were not reactive, all from the synovial fluid of two patients suffering from Chlamydia-induced arthritis. Their cytokine secretion patterns for interferon-gamma (IFN-gamma), IL-2 and IL-4 were analysed, as also were mRNAs for IFN-gamma and IL-10 by in situ hybridization. Out of the 33 antigen-reactive clones 23 showed a Th1 pattern with IFN-gamma but not IL-4 secretion, while the remaining 10 exhibited a Th0 pattern. The clones that did not react with Chlamydia expressed all patterns of cytokine secretion, including a Th2 pattern, thus providing a control population that excludes bias in the sampling procedure. CD4 and CD8 clones displayed a similar cytokine-secretion pattern. In addition this study demonstrates for the first time the expression of IL-10 mRNA in T cell clones derived from synovial fluid, and this was not confined to the Th2 subset. The Th1 response that Chlamydia provoke can be regarded as appropriate for such an obligate intracellular pathogen.

Current perspectives in reactive arthritis

Reactive arthritis (ReA) is an inflammatory arthritis triggered by infection, usually urethritis or gastroenteritis, and is strongly associated with the MHC class I antigen HLA-B27. Two recent observations have excited interest: first, antigen and DNA from the triggering bacteria have been identified in the joint and, second, ReA synovial T cells have been found to respond specifically to the bacterium that caused the initiating infection. Because the trigger of ReA, its onset and the MHC association are all clearly defined, we can investigate hypotheses that are impossible to study in other forms of human arthritis. Here, Gabrielle Kingsley and Jochen Sieper review the topic in the light of a recent workshop.