Immunological abnormalities in juvenile chronic arthritis

Prevalence of IgM-, IgA- and IgG-rheumatoid factors in seronegative polyarticular disease compared to pauciarticular disease in juvenile chronic arthritis as measured by ELISA

OBJECTIVE

To determine the prevalence of the rheumatoid factor isotypes measured by enzyme-linked immunosorbent assay (ELISA) in polyarticular and pauciarticular juvenile chronic arthritis (JCA), and evaluate the diagnostic test qualities.

PATIENTS AND METHODS

53 patients with JCA (20 with seronegative polyarticular disease at onset, 21 with pauciarticular onset and course of disease and 12 with extended pauciarticular disease), as well as 125 control children (58 healthy controls and 67 patients with other diseases) were tested. ELISA for the detection of IgM-, IgA- and IgG-isotypes of RFs was used. The diagnostic characteristics of the tests were evaluated by means of clinical epidemiology methods.

RESULTS

The prevalence of the ELISA for IgG-, IgA-, and IgM-RF for JCA patients vs all controls at optimal cut-off titres was 13%, 29%, and 32%, respectively. The test for IgG-RF was established to be of no significance. IgA-RF had higher prevalence in the polyarticular and extended pauciarticular form, 40% and 33%, respectively. IgM-RF showed a prevalence of 55% for the polyarticular and 42% for the extended pauciarticular form. No significant prevalence has been found in the pauciarticular form.

CONCLUSION

Our results indicate that ELISA for IgG-RF is of no diagnostic value for JCA. The ELISAs for IgM- and IgA-RFs demonstrated a diagnostic significance for the polyarticular and extended pauciarticular form. Juvenile chronic arthritis (JCA) is a heterogeneous disease which encompasses different forms defined by the type of onset. There is evidence, supported by immunogenetic studies that the various subgroups may represent distinct disease entities [1, 2]. Numerous immunological abnormalities have been detected in JCA, but the most characteristic serological findings are ANA and IgM-rheumatoid factor, thought to be useful in the classification of patients and their management. Antinuclear antibodies are universal in JCA, most commonly found in children with early onset pauciarthritis and late onset seropositive polyarthritis [1, 2, 3]. In contrast, the IgM-rheumatoid factor, measured by conventional agglutination techniques, is a hallmark only of polyarthritis with late onset resembling adult rheumatoid arthritis. This group of patients with "seropositive" disease represents less than 20% of all JCA children. Of those patients with "seronegative" disease 20-30% have a systemic onset and the remainder have either a pauciarticular or polyarticular form [2, 3]. Following the introduction of more sensitive techniques, it has already been established that rheumatoid arthritis (RA) patients' sera contain not only the "classical" 19S IgM-RF, but also other isotypes of the rheumatoid factor (RF). A number of studies have emphasized the presence of IgG-, IgA-, IgM- and even IgE- RF in patients with "seronegative" RA [4, 5, 6]. The aim of this study is to determine the prevalence of IgG, IgM and IgA RFs and to attempt at evaluating the diagnostic and prognostic qualities of the ELISA-tests for rheumatoid factor isotypes in polyarticular and pauciarticular forms at onset of JCA.

Juvenile chronic arthritis profile in Greek children

BACKGROUND

Juvenile chronic arthritis (JCA) is the commonest autoimmune rheumatic disease in childhood and presents different clinical subtypes. Juvenile chronic arthritis is considered to be of a polygenic nature and its genetic background is still under investigation. The clinical profile of JCA in the Greek population has not been studied completely. This study retrospectively analyzed the clinical and immunological features of JCA in Greek children presented between 1989 and 1994. Human leukocyte antigen (HLA)-positive or -negative associations in the different clinical subtypes were also detected. The findings of this study were correlated with those reported from other populations.

METHODS AND RESULTS

Antinuclear antibodies (ANA) anti-ds DNA and anti-extractable nuclear antigen antibodies were estimated by immunofluorescent and ELISA assays. Human leukocyte antigen typing was performed by microlymphocytotoxicity, using immunobeads. The peak ages of JCA onset were between 2 and 5 years and also between 9 and 12 years. There was a high female predominance in pauciarticular and polyarticular groups. The most common disease was pauciarticular (58.7%) followed by systemic (25%) arthritis. The incidence of eye involvement was 12.5% and presented only in the pauciarticular group. Overall, ANA positivity was 53.7%, increasing to 90% in pauciarticular cases associated with chronic uveitis. In the early onset (EOPA) pauciarticular subtype, positive-HLA associations with alleles DR11 and DR8 were shown. In the late onset pauciarticular (LOPA) group only B27 allele was increased.

CONCLUSIONS

The results of this retrospective study did not reveal major differences between JCA in Greek children compared with other Caucasian series.

Immune responses to the Escherichia coli dnaJ heat shock protein in juvenile rheumatoid arthritis and their correlation with disease activity

Patients with juvenile rheumatoid arthritis frequently have abnormal immune responses to the hsp65 class of bacterial heat shock proteins. However, lymphocytes from children with other inflammatory diseases may also recognize hsp65, and the role of these antigens in juvenile rheumatoid arthritis remains controversial. We have studied humoral and cellular immune responses to a distinct, recently described bacterial heat shock protein, designated dnaJ. The Escherichia coli dnaJ gene was cloned and expressed, and the purified recombinant protein was used as an antigen. Neither normal children nor children with various chronic inflammatory diseases had lymphocyte proliferative responses to recombinant dnaJ. However, lymphocytes from patients with polyarticular, pauciarticular, and systemic manifestations of juvenile rheumatoid arthritis responded strongly to the antigen. Cellular immune responses to dnaJ were higher in synovial fluid than in blood and higher in children with active disease than in children in remission. These data show that increased immune reactivity to dnaJ is characteristic of juvenile rheumatoid arthritis and that the magnitude of the immune response is linked to disease activity. The results suggest that an abnormal immune response to antigens on commensal gut bacteria may contribute to the generation of chronic inflammation in juvenile rheumatoid arthritis.

Lymphokines and soluble interleukin-2 receptors in juvenile chronic arthritis. Clinical and laboratory correlations

Serum levels of interleukin (IL)-2, interferon gamma (IFNg) and soluble IL-2 receptors (sIL-2R) were determined in sera from 34 patients with poly- or pauciarticular juvenile chronic arthritis (JCA) by use of enzyme-linked immunosorbent assays (ELISAs). Levels of sIL-2R were elevated in the group of patients compared with those of healthy children and correlated significantly with several parameters of clinical activity, including the functional capacity, joint score, visual-analogue score and erythrocyte sedimentation rate (ESR). Serum IL-2 levels were also elevated in the JCA patients, correlating with the patients functional capacity. Serum levels of IFNg were below the detection limit of the assay. Our data supported the notion that T-cell activation plays a role in the immunopathologic processes leading to clinical JCA.

Prevalence of anticardiolipin antibodies in juvenile chronic arthritis

The prevalence of anticardiolipin antibodies was evaluated in 70 children with juvenile chronic arthritis (JCA), in 25 adult patients with rheumatoid arthritis, in 42 healthy children and in 40 adult controls. Thirty seven (53%) patients with JCA were positive for IgG or IgM anticardiolipin antibodies, or both, and 30 (43%) for IgG anticardiolipin antibodies. In contrast, only seven (28%) adult patients with rheumatoid arthritis presented anticardiolipin antibodies, which were of IgG class in four (16%) cases. IgG anticardiolipin antibodies were negative in all control subjects while IgM anticardiolipin antibodies were detected in two (5%) children and in four (10%) adult controls. No correlations were found in patients with JCA between the presence or titres of anticardiolipin antibodies and various clinical or laboratory variables. No patient with anticardiolipin antibodies showed any feature of the anticardiolipin syndrome.

Immunological features of diffuse connective tissue diseases

Diffuse connective tissue diseases (DCTD) represent an heterogeneous group of disorders characterized by systemic inflammatory reactions that are currently classified on clinical grounds. Their aetiopathogenesis is largely unknown and appears to be very complex, associating exogenous factors with an immunogenetic predisposition. In the last decade, studies on human leukocyte antigen (HLA)-disease associations and antinuclear antibodies have provided some useful clues for the diagnosis and clinical management of DCTD.