Expression of the major rheumatoid factor cross-reactive idiotype in juvenile rheumatoid arthritis

Immunoglobulin E-rheumatoid factor in juvenile rheumatoid arthritis

OBJECTIVES

To determine the presence of immunoglobulin E-rheumatoid factor in patients with juvenile rheumatoid arthritis and to correlate it with clinical and laboratory parameters.

METHODS

A multicenter prospective study was carried out from January 1993 to January 1999 with the enrollment of 3 centers of pediatric rheumatology. Ninety-one children with juvenile rheumatoid arthritis diagnosed according to the American College of Rheumatology criteria were studied: 38 (42%) with systemic, 28 (31%) with pauciarticular, and 25 (27%) with polyarticular onset. Ages ranged from 2.1 years to 22.6 years (mean 10.5 +/- 4.7), with 59 (65%) girls. The control group consisted of 45 healthy children. The detection of immunoglobulin E-rheumatoid factor was carried out utilizing an enzyme-linked immunosorbent assay. Associations of immunoglobulin E-rheumatoid factor with immunoglobulin M-rheumatoid factor (latex agglutination test), total serum immunoglobulin E, erythrocyte sedimentation rate, antinuclear antibody, and functional and radiological classes III or IV were analyzed.

RESULTS

Positive immunoglobulin E-rheumatoid factor was found in 15 (16.5%) of the 91 children with juvenile rheumatoid arthritis: 7 (18.5%) with systemic, 5 (18%) with pauciarticular, and 3 (12%) with polyarticular onset. A significant correlation was observed between immunoglobulin E-rheumatoid factor and total serum immunoglobulin E in the juvenile rheumatoid arthritis patients. No correlation was found between immunoglobulin E-rheumatoid factor and positive latex agglutination slide test, erythrocyte sedimentation rate, antinuclear antibody, or the functional and radiological classes III or IV in any disease onset group. In 4 out of 45 control children (8.9%), immunoglobulin E-rheumatoid factor was positive but with no correlation with total serum immunoglobulin E levels.

CONCLUSIONS

Immunoglobulin E-rheumatoid factor could be detected in 16.5% of juvenile rheumatoid arthritis patients, particularly in those with high levels of total serum immunoglobulin E, and immunoglobulin E-rheumatoid factor appears not to be associated with disease activity or severity.

Pediatric rheumatic diseases

The rheumatic diseases of childhood are a relatively common and extraordinarily diverse group of illnesses; nevertheless, they are at least distantly related by similarities of immunodysregulation. These pathophysiologic relationships are reflected in affected children in similarities of historical, physical, and laboratory data as well as therapeutic intervention.

Human rheumatoid factor cross-idiotypes. IV. Studies on WA XId-positive IgM without rheumatoid factor activity provide evidence that the WA XId is not unique to rheumatoid factors and is distinct from the 17.109 and G6 XIds

The WA cross-idiotype (XId) is the major XId among human monoclonal rheumatoid factors (mRF) and is almost always associated with the light (L) chain XId, 17.109, and the heavy (H) chain XId, G6. A cell line, 35G6, was cloned that bears the WA XId, but shows no reactivity with immunoglobulin G (IgG) and is negative for the 17.109 and G6 XIds. The 35G6 L chain appears to be derived from the same VKIII-JKI genes as most WA mRFs L chains. In contrast to the WA mRFs H chains in which VH1 genes are used, the 35G6 IgM expresses a VH3 gene. Sequence comparisons with other WA XId-positive mRF suggested several common structural features that may be related to the WA XId and differences that may relate to lack of IgG reactivity. Cells similar to 35G6 have previously been described in pokeweed mitogen-stimulated cell lines of peripheral blood lymphocytes from normal individuals and patients with rheumatoid arthritis and type II mixed cryoglobulinemia. These observations were confirmed, and in addition, it was shown that the majority of WA XId-positive cells in these cultures were negative for the 17.109 and G6 XIds. The presence of the WA XId in the absence of IgG reactivity suggests that the WA XId is more directly associated with an antigen specificity other than IgG, and its association with RF activity may be incidental. It is postulated that these WA XId-positive RF-negative antibodies may serve a physiologic role as natural antibodies to a pervasive pathogen, and that IgG reactivity is a consequence of somatic diversification accompanying proliferation of the WA XId-positive RF-negative cell.

Immunological aspects of juvenile rheumatoid arthritis

This article reviews the evidence from recent studies on immunological abnormalities associated with pathophysiologic mechanisms operating in three clinical subtypes of juvenile rheumatoid arthritis (JRA) (polyarticular, pauciarticular and systemic). The main discussion is focused on three hallmarks of immunopathological studies. First, abnormalities in phenotype and function of lymphocytes from peripheral blood and inflamed synovium are discussed. The aberrations of lymphocytes are elucidated by T and B cells expressing phenotypic cell-markers such as CD20, CD21, CD4, CD8 and DR in association with different subtypes and disease activity. The functional imbalance and impairment of T and B cells are mainly observed by abnormal proliferation and/or in vitro Ig production in response to mitogens and alloantigens. Second, because the appearance of rheumatoid factors (RF) in serum indicates that the pathogenesis of JRA may be based on the autoimmune mechanism, the prevalence of RF including IgM, IgA and IgG isotype, hidden IgM RF and cross-reactive idiotype RF, and their characteristic properties are discussed. Moreover, specific auto-antibodies (antinuclear antibodies and others) for JRA are illustrated in this paper. Third, the production of various pro-inflammatory cytokines resulting in the release of tissue-damaging chemical mediators is also discussed. This may play a central role in the generation of systemic inflammation and joint involvement in JRA.

Autoantibody studies in juvenile rheumatoid arthritis

Early studies showed few immunologic abnormalities in juvenile rheumatoid arthritis (JRA) patients. There were no specific laboratory markers useful for diagnosis and assessment of the course of disease in JRA. Previous work showed an association of antinuclear antibodies (ANA) with early-onset pauciarticular disease and iridocyclitis. Similarly, the presence of 19S immunoglobulin (Ig) M rheumatoid factors (RF) was associated with late-onset polyarticular disease in girls. More recent studies have detected many unique autoantibodies. Newer assays show 19S IgM RF in up to 35% of JRA patients, although still mainly in girls with late-onset polyarticular disease. Hidden 19S IgM RF can be shown in up to 75% of JRA patients using different procedures, primarily in those with active polyarticular-or pauciarticular-onset disease. Immune complexes have been detected in JRA patients by means of different techniques; their presence usually correlates with active disease. Studies on a specific ANA in JRA have shown no common extractable nuclear antigen, but antihistone antibodies have been found in up to 75% of cases, again mainly in those with pauciarticular onset and iritis. Finally, a variety of unusual immunologic proteins have also been detected, including anti-ocular, anti-cellular, anti-cardiolipin, anti-perinuclear factor, and anti-collagen antibodies. This review evaluates the significance of these antibodies that can now be found in JRA.

The major rheumatoid factor cross-reactive idiotype is dominantly expressed by Staphylococcus aureus Cowan strain I-activated CD5+ control B cells

Some seropositive (RF+) and seronegative (RF-) rheumatoid arthritis (RA) patients selectively express high concentrations of the major RF cross-reactive idiotype (RCRI) in their sera and generate high frequencies of RCRI+ pokeweed mitogen (PWM)-induced plasma cells from their peripheral blood mononuclear cells (PBM). To determine if normal individuals can express RCRI in vitro, B cells from controls were activated with Staphylococcus aureus Cowan strain I (SAC) bacteria to identify RCRI and RF production. In addition, we studied the relationship of RCRI expression with the subset of B cells bearing CD5. Control CD5+ B cells are responsible for RCRI expression following SAC activation. We also observed that RCRI is dominantly expressed by control SAC-induced B cells in frequencies comparable to that expressed by some RA and juvenile rheumatoid arthritis patients' PBM activated by PWM. Therefore, the frequency of RCRI+ B cells in control and arthritis patients' PBL may be similar, or the selection and/or regulation of RCRI+ B-cell expression in vitro and in vivo may be different in arthritis patients compared to normal individuals.

Expression of the rheumatoid factor cross-reactive idiotype in JRA: association with disease onset subtype, disease activity and disease severity

We previously reported that approximately one-third of patients with juvenile rheumatoid arthritis (JRA) express high concentrations of antibodies marked by the rheumatoid factor cross reactive idiotype (RCRI) in their sera (6). In order to determine if an expression of RCRI is associated with certain clinical features of the disease, we prospectively studied 49 patients with JRA over a six month period, and determined serum RCRI concentrations by inhibition ELISA. RCRI concentrations correlated significantly with the duration of morning stiffness (r = .3866, p less than .01), and the functional class (p less than .001), but not with the number of active joints. Expression of RCRI was higher in patients with systemic onset disease (p less than .03), compared to patients with pauciarticular or polyarticular disease. In patients studied on more than one occasion, the RCRI expression was relatively constant despite changes in disease activity. A subset of JRA patients with systemic onset disease, higher serum concentrations of the RCRI.

Hidden rheumatoid factor and Wa idiotype expression in juvenile rheumatoid arthritis

The major rheumatoid factor cross-reactive idiotype, which was defined by prototypic monoclonal IgM rheumatoid factors from Waldenstrom's macroglobulinaemia patient Wa, is present on 60% of all monoclonal IgM RF paraproteins. One-third of patients with juvenile rheumatoid arthritis (JRA), who are seronegative for classic IgM rheumatoid factor (RF), express the Wa idiotype in high titre in their sera. To determine if the Wa idiotype is present on hidden rheumatoid factors in JRA patient sera, we studied hidden RF expression by both ELISA and haemolytic assay techniques. The majority of JRA sera with increased concentrations of the Wa idiotype did not have increased RF activity nor hidden RF activity. In some JRA patients, the Wa idiotype may be expressed on a parallel set of immunoglobulin molecules, related to RFs, but lacking the ability to bind to IgG.

Expression of the major rheumatoid factor cross-reactive idiotype in pediatric patients with systemic lupus erythematosus

Rheumatoid factor cross-reactive idiotype (RF-CRI) is expressed in high concentrations in the sera of some patients with rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA). To determine if RF-CRI is specifically expressed in rheumatic disease or if it is secondary to polyclonal B-cell activation, we examined sera of 23 children with SLE, 16 adolescents with infectious mononucleosis (IM), and age-matched pediatric controls for RF-CRI expression. Concentrations of RF-CRI in serum, determined by an inhibition ELISA, were 24 +/- 17 micrograms/ml (mean +/- SD) in 25 normal children, 31 +/- 17 in 16 young adults with IM, and were significantly increased, 70 +/- 80 micrograms/ml, in the 23 children with SLE (p less than 0.036). Eleven of 23 SLE patients had serum RF-CRI greater than the mean +/- 2 SD for normal children. Ten of 23 SLE sera contained IgM rheumatoid factor (RF) activity. One patient with IM had a borderline elevated RF-CRI level, and 5 IM patients had RF in their sera. The serum IgM concentrations in sera were: SLE (192 +/- 93 mg/dl) and IM (234 +/- 77 mg/dl) sera. These levels were significantly elevated compared to controls (132 +/- 44 mg/dl), p less than 0.031 for SLE and p less than 0.001 for IM, suggesting that polyclonal activation of B cells was present in SLE and IM patient groups. Increased expression of RF-CRI in the SLE patients correlated directly with high titer anti-DNA antibody values (r = 0.3965, p less than 0.05) and RF activity when human IgG (r = 0.5026, p less than 0.05) was used as the RF binding substrate and inversely with serum C3 levels (r = 0.3925, p less than 0.05). RF-CRI expression did not correlate with RF that bound rabbit (r = 0.3123, p greater than 0.05). Increased serum RF-CRI expression is not a result of polyclonal B-cell activation. RF-CRI may be selectively up-regulated in patients with SLE.

Expression of large quantities of rheumatoid factor major cross-reactive idiotype in the serum of adults with seropositive rheumatoid arthritis

We quantified rheumatoid factor cross-reactive idiotype (RF-CRI) in whole serum from RF+ rheumatoid arthritis (RA) patients, using an inhibition enzyme-linked immunosorbent assay which is not affected by the presence of IgG. Serum from 16 RF+ RA patients contained 2-252 micrograms/ml RF-CRI (geometric mean */divided by SD 20.8 */divided by 5.2), while serum from 11 normal adults contained 1-16 micrograms/ml RF-CRI (geometric mean */divided by SD 3.9 */divided by 2.3). Serum from 8 of the RF+ RA patients contained RF-CRI at concentrations more than 2 standard deviations above the geometric mean in the normal subjects (greater than 21 micrograms/ml). Our results indicate that some RF+ RA patients express high concentrations of RF-RCRI and immunoglobulin molecules that express the RF-CRI may not be RF.

Idiotypic analysis of human anticentromere autoantibodies

The idiotypes (Ids) of anticentromere antibodies (ACA) have been studied using a fusion protein obtained from cloned cDNA of the major centromere antigen, CENP-B, for isolation of the autoantibodies. IgG-ACA were affinity purified from 4 patient sera and anti-Ids prepared in rabbits. Analysis revealed the existence of two distinct types of immunodominant Ids. One Id is near the antibody combining site and one is framework associated. A longterm longitudinal study of Id expression in a patient who seroconverted from ACA (-) to ACA (+) when she developed Raynaud's phenomenon showed a close correlation between Id expression and ACA titers (r = 0.94). These results may be interpreted as evidence for an autoantigen driven process in the anticentromere immune response.

Idiotypes and autoimmunity

The reports discussed above have increased our knowledge of idiotypes, mainly with respect to additional CRI on autoantibodies and to a relatively new aspect of 'pathogenic idiotypes'. It is obvious that much remains to be discovered about the normal role of idiotypes and how they might be involved in the pathogenesis of autoimmune disorders. The relationship of the idiotypic network to tolerance is a matter of speculation; tolerance implies the ability to distinguish between 'foreign' and self-antigens and it is important to remember that antibody V regions are also self-antigens. Several mechanisms have been proposed to explain immunological tolerance. Originally, it was envisaged that the repertoires of both T and B lymphocytes were in some way purged of potentially self-reactive clones. However, it is now evident that self-reactive lymphocytes do exist but are normally held under control. Finally, it may be that certain self-antigens are simply never exposed to immune surveillance. It seems that the control of self-reactive lymphocytes is central to the question of tolerance. In the absence of autoimmune disease, autoantibodies can be produced, for example, after many infectious diseases or vaccinations. However, this type of perturbation of the immune system is associated with the short-term production of low titres of low-affinity antibodies, generally of the IgM isotype, which are thought to represent germline gene products. Homeostasis is soon re-established, possibly by regulatory T cells interacting with autoreactive B cells through their idiotypic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

The major rheumatoid factor cross-reactive idiotype in rheumatic disease

The major rheumatoid factor cross-reactive idiotype (RCRI), a tertiary structure formed by both light and heavy chains, is found on 60% of all monoclonal IgM kappa RFs. To determine if the RCRI is expressed in patients with rheumatic disease, we used polyclonal rabbit anti-idiotypic antibodies to detect RCRI in sera and in pokeweed mitogen cultures of blood mononuclear cells (PBM) from patients with rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA). We detected increased expression of RCRI+, plasma cells in PWM cultures, and in sera from these patients. We have determined that some 7S IgM molecules from RF+RA patients are RCRI+, and can bind IgG in a sensitive RF ELISA. We have also observed that the CD5+ B cell subset, which is responsible for autoantibody production, generates RCRI+ antibodies. We review these data and discuss the relationship of the idiotypic network of interacting antibodies with rheumatic disease.