IgM rheumatoid factor (RF), IgA RF, IgE RF, and IgG RF detected by ELISA in rheumatoid arthritis.

One hundred patients with rheumatoid arthritis (RA), of whom 73 were seropositive by latex or Waaler-Rose (WR) assays, or both, 100 healthy subjects, and 102 diseased controls (22 patients with systemic lupus erythematosus (SLE) and 80 with bronchial asthma) were evaluated for the presence of IgM rheumatoid factor (RF), IgA RF, IgE RF, and IgG RF by an enzyme linked immunosorbent assay (ELISA). Ninety two per cent, 65%, 68%, and 66% of the patients with RA were found to be positive for IgM, IgA, IgE, and IgG respectively. A positive correlation existed between the levels of IgM RF and IgA RF on the one hand and disease activity on the other, and the levels of IgM RF and IgA RF correlated with the levels of circulating immune complexes as measured by a C1q binding assay. The presence of extra-articular features also correlated positively with the levels of IgA RF and IgE RF. Five out of six patients with Sjögren''s syndrome had very high levels of IgA RF. Of 47 patients typed for HLA-DR, DR1 and DR2 were significantly more frequent in those with the highest levels of IgM RF. Conversely, DR3 was associated with low levels or absence of IgA RF and IgE RF. These results suggest that immune response genes may regulate the level of different RF isotypes. The frequencies of IgM, IgA, IgE, and IgG RF were 59%, 36%, 9%, and 27% respectively in SLE and 25%, 2.5%, 70%, and 59% in bronchial asthma.     

Rheumatoid factors in rheumatoid arthritis and vasculitis

Summary To study the occurrence of rheumatoid factors (RF) in relation to the activity of rheumatoid arthritis and the occurrence of vasculitis, RF of IgM, IgA, and IgG classes were measured in sera from 35 patients with definite or classic rheumatoid arthritis (RA) using ELISA. For 26 patients, the RF levels were studied longitudinally and compared with changes in the articular index. Although IgM RF was occasionally found in patients without RA, IgA and/or IgG RF were almost exclusively associated with RA. The titers of IgM, IgA, and IgG RF were significantly higher in sera from patients with clinically diagnosed rheumatoid vasculitis than in sera from patients without vasculitis. No significant correlation between changes in the articular index and changes in titer of any class-specific RF could be found for the group of RA patients as a whole. However, in individual patients, increases or decreases in IgM and IgG RF titer were significantly correlated with an increase or decrease in the articular index.     

Isotypes of rheumatoid factors in rheumatoid arthritis and chronic liver diseases

We studied isotype-specific rheumatoid factors (RFs) to clarify their significance in rheumatoid arthritis (RA) and to verify the difference in RF isotypes between RA and chronic liver diseases (CLD). Isotype-specific RFs in RA and in CLD were measured by enzyme-linked immunosorbent assay (ELISA). Most sera (n = 51, 94.1%) from RA patients contained some kind of RF isotypes (92.1% for IgM RF, 76.4% for IgG RF, and 43.1% for IgA RF), and seronegative RA by ELISA was seen in only 11.8% (n = 6). The most characteristic combination of RF isotypes in active RA was IgG, IgA, and IgM. This combination of RF isotypes changed to IgG plus IgM, according to the diminution of RA activity; then, we found only IgM RF in inactive RA. The titers of each RF isotype also decreased in parallel with the activity of RA. IgA RF seemed to be the most sensitive factor for evaluating the activity of RA. In CLD, almost the same high frequency (n = 49, 89.8% for IgM RF, 59.2% for IgG RF), with the same titer levels seen in RA, was observed. On the other hand, IgA RF was significantly lower in frequency (n = 9, 18.4%) and in titer, compared with the finding in RA. Surprisingly, even in CLD, true seronegativity by ELISA was also found in very few patients (n = 4, 8.1%). In CLD, positive RFs detected by agglutination assay were seen more often in chronic hepatitis than in liver cirrhosis. In RA patients, significant associations of IgA RF and the serum concentration of IgA, and IgG RF and the serum concentration of IgG, were observed. On the other hand, in CLD patients, significant associations of IgG RF and the serum IgG concentration, and of IgM RF and the serum IgM concentration, were observed. These results indicated that IgA RF in active RA is the most characteristic RF isotype distinguishing it from other nonrheumatic diseases, as well as from inactive RA. RF isotypes reflected the background polyclonal B-cell activation in different manners in both diseases. In CLD, RF isotypes seemed to be disease-related immunological disorders reflecting disease progression. Received: February 17, 2000 / Accepted: July 5, 2001     

Population study of the importance of rheumatoid factor isotypes in adults.

Blood samples collected from 13,858 randomly selected subjects participating in a health survey in Iceland from 1974 to 1983 were tested for rheumatoid factor. Samples that were positive in a sensitive RF screening test were analysed further by the Rose-Waaler technique and an isotype specific enzyme linked immunosorbent assay (ELISA). In 1987 the 173 available participants who were RF positive and 156 matched RF negative controls were evaluated clinically for rheumatoid diseases. RF levels and isotype patterns were more persistent in the patients with rheumatoid arthritis (RA) than in RF positive subjects who did not have overt RA. The prevalence of RA was only 19% in the participants who were RF positive in 1987. Forty per cent of the participants who had a persistent (four to 13 years) increase of IgA RF combined with either IgM or IgG RF were diagnosed as having RA. A positive correlation was found between RF levels and various manifestations of RA. This association was stronger for the IgA and IgG RF isotypes than for IgM RF. Excluding RF positivity as a diagnostic parameter, RA was diagnosed in 33 of the participants and 20 (61%) of these patients had increased levels of IgM and IgA RF. Patients with RA with bone erosions in their hands had higher levels of IgA RF than patients without erosions, but an association was not found between bone erosions and other RF isotypes. None of the RF negative participants who were symptom free when the original blood sample was taken developed RA during the four to 13 year follow up period. In contrast, five symptom free RF positive participants developed RA during this period. These five patients had all had increased levels of at least two RF isotypes before the onset of their symptoms. It is concluded that the IgA and IgG RF isotypes have a closer association with the clinical parameters of RA than IgM RF. Furthermore, increases in RF can precede clinical manifestations of RA and this applies in particular to the IgA and IgG RF isotypes.     

Prospective study of early rheumatoid arthritis. II. Association of rheumatoid factor isotypes with fluctuations in disease activity.

Thirty-three patients with early peripheral synovitis were followed up for two to four years in order to study the relationship between fluctuations in rheumatoid factor (RF) levels and indices of clinical activity. Twenty-eight of these patients developed classical/definite rheumatoid arthritis (RA). Seventeen patients developed erosive disease of their hands and wrists and thirteen had a positive RF agglutination test. Nineteen patients had raised levels of IgM, RF, IgA, RF, or IgG RF as measured by isotype-specific ELISA techniques. The within-patient fluctuations in IgA RF levels correlated significantly with the corresponding fluctuations in grip strength (p less than 0.05), erythrocyte sedimentation rate (ESR) (p less than 0.01), and a composite index of disease activity (p less than 0.02). IgG RF levels were also associated with changes in ESR and grip strength, but IgM RF showed only a weak association with fluctuations in ESR and not with any other clinical parameters. It is suggested that serum IgA RF may be a useful marker of disease activity in rheumatoid arthritis.     

Class specific rheumatoid factors in rheumatoid arthritis: response to chrysotherapy and relationship to disease activity

IgG rheumatoid factors (RF) may play an important role in the pathogenesis of rheumatoid arthritis (RA). Our study investigates the relationship between class specific RF levels measured by radioimmunoassay and disease activity in patients with RA undergoing chrysotherapy. Nineteen patients were treated with 20 mg disodium aurothiomalate weekly for 6 months. Rheumatoid disease activity was assessed before and after 6 months' treatment and the level of IgG, IgA and IgM RF measured. There were significant falls in disease activity (p less than 0.005), IgA RF (p less than 0.005) IgG RF (p less than 0.005) and SCAT (p less than 0.025), but not IgM RF, over the 6 month treatment period. No correlation was found between absolute levels of IgA, IgG or IgM RF and disease activity before or after 6 months' therapy but there was a highly significant linear correlation between reduction in IgG RF levels and fall in disease activity (r = 0.642, p less than 0.005) with treatment.     

Rheumatoid factors in psoriatic arthropathy and in Waaler-Rose negative rheumatoid arthritis

Summary Serum levels of IgG, IgA and IgM rheumatoid factor (IgG RF, IgA RF and IgM RF) were determined by means of the diffusion-in-gel enzyme-linked immunosorbent assay (DIG-ELISA) in 42 Waaler-Rose negative patients with psoriatic arthropathy (PsA) type 1 (arthritis with involvement of distal interphalangeal joints) and type 3 (polyarthritis of rheumatoid type) according to the criteria of Moll and Wright as well as in 53 patients with Waaler-Rose negative rheumatoid arthritis (RA). Elevated levels of RF were found in 22% of patients with PsA type 3 and 45% of patients with Waaler-Rose negative RA. In contrast, none of the patients with PsA type 1 had detectable amounts of RF. It is suggested that the presence of IgG, IgA or IgM RF in patients having psoriasis in conjunction with inflammatory polyarthritis indicates the RA nature of the joint disease and should be considered as exclusion criterion for the diagnosis of PsA.     

Enhancement of Clq binding activity by IgM rheumatoid factor

Clq binding activity (ClqBA) averaged 18.1 +/- 14.5% (1 SD) in 28 rheumatoid arthritis (RA) sera (normal sera = 3.9 +/- 0.4%). Further analysis indicated that rheumatoid factor (RF) positive [RA (+)] sera averaged 30.4% ClqBA, significantly greater than the 3.9% ClqBA in RA RF negative [RA(-)] sera (p less than 0.01). In the RA(+) sera, RF titer correlated with ClqBA (r = +0.73). Addition of IgM RF to sera of normal, SLE, and RA(-) patients, as well as to aggregated IgG and reduced and alkylated aggregated IgG, resulted in significant increases in ClqBA, up to 14% in the latter group (p less than 0.01). Control IgM added to these same systems had no effect on ClqBA. IgM RF only slightly increased Clq binding of monomeric IgG.     

Measurement of rheumatoid factors by an enzyme-linked immunosorbent assay (ELISA) and comparison with other methods.

IgM rheumatoid factor (RF) was measured in the sera of 48 rheumatoid patients and of 48 age and sex-matched normal controls by the Rose-Waaler and latex agglutination tests, a rate nephelometer, and an enzyme-linked immunosorbent assay (ELISA). Good correlation was obtained between all assays. The rate nephelometer assay was the easiest and quickest to perform and gave results in international units/ml. The Rose-Waaler was the least sensitive assay and the most difficult to perform and interpret. Both the latex agglutination and the ELISA were sensitive, though some overlap of patient and control sera was seen with all the assays. In addition to IgM RF the ELISA was used to measure IgG RF and IgA RF in both rheumatoid and control sera. Although some normal sera had detectable amounts of IgG and IgA RF, the levels of both were significantly raised in the rheumatoid sera. IgG RF levels were lower after pepsin digestion of the sera, suggesting that IgM RF interfered with the assay for IgG RF unless this treatment was included.     

Effect of circulating immune complexes on the binding of rheumatoid factor to histones

OBJECTIVE: To determine whether the reaction of rheumatoid factor (RF) with solid phase histone is due to the simultaneous presence of circulating immune complexes (CICs) or aggregated IgG. METHODS: Serum samples from 56 patients with seropositive rheumatoid arthritis (RA) and 50 random blood bank donors were used. Binding of immunoglobulins to histone was determined by enzyme linked immunosorbent assay (ELISA) and by western blots. Aggregated IgG was obtained by heating at 61(o)C for 30 minutes. RESULTS: Among the RA sera tested by ELISA, 54% were positive for histone binding by IgM, IgG, or IgA and 20% by IgM only. Heating of normal sera caused a significant enhancement in the binding of IgG to histone (p<0.001). This binding had a non-cognate behaviour-that is, it was destroyed by pepsin treatment of serum and was not significantly inhibited by competition with free histone. The same behaviour was seen for IgM, IgG, and IgA binding from RA sera. However, cognate IgG antibody binding to histone was inhibited by free histone and was resistant to pepsin digestion. Addition of heat aggregated IgG to RA sera or pretreatment of histone with aggregated IgG caused a significant increase in IgM binding to histone. CONCLUSION: IgM, IgG, and IgA RF bind to solid phase histone as a result of attachment to histone of immune complexes or aggregated IgG and not as a result of a cognate reaction with histone.     

The predictive value of rheumatoid factor isotypes, anti-cyclic citrullinated peptide antibodies, and antineutrophil cytoplasmic antibodies for mortality in patients with rheumatoid arthritis

OBJECTIVE: To evaluate the significance of rheumatoid factor (RF) and its isotypes (IgA RF, IgG RF, and IgM RF), anti-cyclic citrullinated peptide antibodies (anti-CCP), and antineutrophil cytoplasmic antibodies (ANCA) in predicting mortality in patients with rheumatoid arthritis (RA). METHODS: The study population comprised 604 patients with RA participating in a cross-sectional study in 1987. Presence of RF (n = 604), RF isotypes (n = 206), anti-CCP (n = 184), and ANCA (n = 200) were determined in these patients from available baseline sera. Vital status was assessed in 1999 and multivariate Cox regression analysis used to compare mortality in RA patients with or without different antibodies. RESULTS: Of the 604 patients with RA, 55% were positive for RF, 66% for anti-CCP, and 14.5% for perinuclear ANCA. Twelve patients (19%) with RF were anti-CCP-negative and 34 (40%) without RF were anti-CCP-positive. Of the total 604 patients, 160 had died by 1999. Positive RF and high IgA and IgM RF levels predicted increased mortality, while positive anti-CCP or ANCA did not. However, high anti-CCP levels were related to an increased mortality risk. CONCLUSION: Patients with RA with positive RF, especially IgA and IgM isotypes, carry a risk of dying earlier than patients without these serological findings.     

Comparative study of different enzyme immunoassays for measurement of IgM and IgA rheumatoid factors

OBJECTIVE: To compare the value of various IgM and IgA rheumatoid factor (RF) tests for the diagnosis of rheumatoid arthritis (RA). METHODS: Firstly, the latex test, one global assay (for IgM, IgA, and IgG RF), six IgM, and four IgA RF assays were compared in a particularly challenging situation-that is, with 67 patients with RA, many of whom were latex negative, and 91 non-RA controls, many of whom were latex positive. More detailed evaluation followed with three IgM RF tests (two commercially available kits and one assay developed in our laboratory) and two IgA RF tests (one commercially available and one from our laboratory) in two more representative samples of rheumatological patients (146 RA and 75 non-RA controls). RESULTS: Diagnostic performance differed considerably between the assays. For IgM RF detection the highest sensitivity (88%) was obtained with the Diamedix kit (specificity 67%) and for IgA RF with the Inova kit (sensitivity 65%, specificity 88%). Combining one IgM and one IgA RF test improved diagnostic performance when both tests were in agreement, but at the cost of yielding 15-27% of discrepant results which did not help in ruling RA in or out. Mean concentration values differed significantly among IgM RF tests, and in most cases concentrations were not correlated. CONCLUSIONS: Available tests for IgM RF isotype vary in accuracy, and none is uniformly better than all the others. For IgA RF isotype, the Inova kit appears to be the best. Quantitative results cannot be compared across tests. Combination of one IgM and one IgA RF test may improve diagnostic accuracy.     

Serum antiimmunoglobulins reactive with human and rabbit IgG in rheumatoid arthritis and other conditions

IgG, IgA, and IgM antiimmunoglobulins reactive with human and rabbit IgG were measured in patients with rheumatoid arthritis (RA), patients with rheumatic fever or osteoarthritis, and normal individuals. Values of all antiimmunoglobulins were significantly evaluated in RA patients as compared with other groups and depended upon activity and stage of the disease. IgM antibodies with specificity for human IgG predominated quantitatively over others in sera of RA patients with high titers of RF, whereas most of those reactive with rabbit IgG in latex negative or positive RA patients belonged to IgG class. The reaction with human IgG included thermostable and thermolabile IgM antiimmunoglobulins but in that with rabbit IgG only thermostable antibodies were active.     

Effects of rheumatoid factor isotypes on disease activity and severity in patients with rheumatoid arthritis: a comparative study

The value of rheumatoid factor (RF) isotypes for assessing rheumatoid arthritis (RA) remains debatable. In this study, we have examined the relationships between RF isotypes and disease activity and severity in RA patients. Sixty-two patients with RA, 48 women and 14 men, were studied. RF was measured by nephelometry (RF–N) and IgG–, IgA–, and IgM–RF isotypes were measured using enzyme-linked immunosorbent assay. Serum C-reactive protein and erythrocyte sedimentation rate were also determined. The patients were classified according to disease activity, joint damage, functional status, and presence of pulmonary involvement, rheumatoid nodule, and secondary Sjögren’s syndrome. Although the patients with active disease had significantly higher IgA–RF and IgM–RF levels compared to inactive patients, IgA–RF and IgM–RF were not found to be independently associated with disease activity in multivariate analysis. In patients with severe joint damage, IgA–RF and RF–N were significantly higher than those of the other patients. Multiple regression analysis showed that IgA–RF was the unique variable independently associated to severe joint damage. The patients with class III and IV functional index had significantly higher IgM–RF, IgA–RF, and RF–N levels compared to the patients with class I and II functional index; however, RFs were not significantly associated with functional status in multivariate analysis. IgA–RF and IgM–RF were significantly associated with pulmonary involvement and rheumatoid nodule, respectively. No significant associations were found between RF isotypes and secondary Sjögren’s syndrome. Our results suggest that the clinical usefulness of IgA and IgM isotypes is better than RF–N. Elevated IgA–RF may be a marker of erosive disease. The usefulness of RF isotypes for monitoring disease activity or functional status appears to be limited.     

Clinical significance of rheumatoid factor--its complement activating property and isotype]

We investigated the relationship between complement-activating properties of rheumatoid factors (RF) and their isotypes. Active and inactive RA patients without extra-articular symptoms (EAS) and those with EAS were studied. Patients with SLE, liver cirrhosis (LC) and normal volunteers were served as controls. Isotype of RF was measured by ELISA and complement activation (CA) of RF was measured by hemolytic assay. The CA values were significantly higher in RA patients with EAS than those in RA patients without EAS and with other diseases. The IgG and IgM-RF values were significantly higher in active RA without EAS than in inactive RA. Positive correlations between IgM-RF values and CA values were observed in RA with or without EAS, SLE and LC. The Sephadex G-200 gel filtration analysis of sera revealed CA in only 19S IgM fraction. Additionally, we purified 19S IgM-RF from sera of RA, SLE and LC patients by affinity chromatography, and found 19S IgM-RF had CA. These data suggest that serum IgM-RF may play a critical role in the pathogenesis of RA, especially in RA with EAS.     

The prevalence of rheumatoid factor isotypes and anti-cyclic citrullinated peptides in Malaysian rheumatoid arthritis patients

Aim: The purpose of this study is to compare the prevalence of rheumatoid factor (RF) isotypes and second generation anti‐cyclic citrullinated peptides (anti‐CCP) in Malaysian rheumatoid arthritis (RA) patients. Methods: In this cross‐sectional study, 147 established RA patients from three ethnic groups were recruited from a major rheumatology clinic in Malaysia. Enzyme‐linked immunosorbent assays (ELISA) for serum RF isotypes IgA, IgG and IgM as well as second‐generation anti‐CCP were performed and the prevalence of each auto‐antibody was compared in the three ethnic groups. Results: The anti‐CCP was the most prevalent auto‐antibody in each of the ethnic groups, followed closely by RF IgM and RF IgG. Rheumatoid factor IgA was the least prevalent across all three ethnic groups. The anti‐CCP–RF IgM combination provided the best test sensitivity. Seroprevalence of anti‐CCP was strongly associated with the presence of each of the RF isotypes. The seroprevalence of RF and anti‐CCP did not increase or decrease with advancing age, age at onset and disease duration. Conclusion: When used alone, anti‐CCP provides a diagnostic advantage over RF IgM on the basis of test sensitivity. Considering the high cost of the anti‐CCP assay, step‐wise serum testing with IgM RF followed by anti‐CCP may provide a more economically sensible option to optimize test sensitivity for RA.     

Autoantibodies can be prognostic markers of an erosive disease in early rheumatoid arthritis

OBJECTIVE: To evaluate a contribution of selected laboratory parameters for a prediction of progressive and erosive development in patients with early rheumatoid arthritis (RA). METHODS: In a prospective study baseline levels of antibodies to cyclic citrullinated peptide (anti-CCP), IgM, IgA, and IgG rheumatoid factors (RFs) were measured by enzyme linked immunosorbent assay (ELISA) in 104 patients with RA with disease duration <2 years. Antikeratin antibodies (AKA) and antiperinuclear factor (APF) were detected by indirect immunofluorescence. Patients were divided into two groups based either on the presence or absence of erosions or according to progression of Larsen score at the end of the 24 months' follow up. RESULTS: Sixty seven (64%) patients developed radiographic erosions, 49 (47%) had progression in Larsen score, and 36 (35%) progressed by more than 10 Larsen units. Significant differences in erosions and progression between the two groups were detected for anti-CCP, AKA, APF, IgM RF, IgA RF, and IgG RF. Baseline Larsen score correlated significantly with anti-CCP, IgM RF, and IgA RF levels, and all measured antibodies correlated with the progression >10 units. The combination of anti-CCP and IgM RF increased the ability to predict erosive and progressive disease. CONCLUSION: The data confirmed that measurement of anti-CCP, AKA, APF, and individual isotypes of RFs was useful for prediction of structural damage early in the disease course. Combined analysis of anti-CCP and IgM RF provides the most accurate prediction.     

IgM,IgA and IgG rheumatoid factors in patients with rheumatoid arthritis and normal donors

Summary IgM, IgA, and IgG Rheumatoid Factors (RF) were measured by ELISA assay in serum from 26 patients with definite rheumatoid arthritis (RA) and 11 normal controls. IgM-RF was assayed by ELISA, radioimmunoassay,and also by the standard latex fixation test in all sera from RA patients. In patients with RA quantitative amounts of IgM, IgA, and IgG-RF as estimated by ELISA were highly correlated. Significant correlations were found between a physician's rating of disease activity and IgG-RF (r=0.44; p<.02) and IgA-RF (r=0.38; p=.06 but not for IgM-RF as measured in any of the three assays.During the course of this work F.S. was supported by a NATO fellowship from the Consiglio Nazionale delle Ricerche, Roma, Italy.     

Prospective study of early rheumatoid arthritis. I. Prognostic value of IgA rheumatoid factor.

Thirty-three patients with early arthritis, 28 of whom developed classical/definite rheumatoid arthritis (RA), were followed up for two to four years. Rheumatoid factor (RF) levels of the IgM, IgA, and IgG isotypes were measured in serum and synovial fluid by an ELISA technique developed in our laboratory. All seven patients who presented with raised IgA RF developed erosions of their hands and wrists. This was significantly different from the remaining 26. By contrast none of the five patients who presented with isolated elevation of IgM RF developed erosive disease. The patients with raised IgA RF needed significantly more treatment with 'specific' drugs than the remaining 26. It is suggested that the detection of IgA RF in early RA indicates poor prognosis, justifying a more aggressive treatment at an early stage.     

Rheumatoid factor isotypes and circulating immune complexes in rheumatoid arthritis

Solid phase enzyme immunoassays were here used to quantify rheumatoid factors (RF) of the IgM, IgG and IgA classes and the immune complexes (IK) by their ability to bind to C1q or conglutinin in both the serum and synovial fluid of patients with rheumatoid arthritis (RA). Elevated serum levels of any RF isotype could be found in all patients with seropositive RA (IgM: 63%, IgG: 87%, IgA: 90%). Seronegative patients with RA presented to a significantly lesser extent with elevated levels of all the RF isotypes tested (IgM: 0%, IgG: 40%, IgA: 32%). Synovial fluid RF levels were significantly higher in SPRA patients than in SNRA patients with the exception of IgG-RF. All of the RF classes in both RA groups, however, were elevated when compared to RF in the synovial fluid of patients with osteoarthrosis. Both C1q binding and conglutinin binding immune complexes were significantly higher in the synovial fluid than in the serum of RA patients. The erythrocyte sedimentation rate and plasma iron levels were correlated with the levels of C1q binding immune complexes (IC) in the synovial fluid; total iron binding capacity showed an inverse relationship to synovial fluid IgG-RF levels. A radiographic index was also correlated with IgG-RF levels in the synovial fluid. Extraarticular manifestations were significantly more frequent in patients with elevated serum levels of IgM-RF or conglutinin binding IC. These findings indicate that IgG-RF in the synovial fluid and the formation of IC determined by their ability to bind C1q seem to be closely related to clinical features of local disease.(ABSTRACT TRUNCATED AT 250 WORDS)