IgG antiglobulins in rheumatoid arthritis and other arthritides: relationship with clinical features and other parameters.

A radioimmunoassay has been developed for measuring IgG antiglobulins using baboon IgG as antigen. Raised levels were virtually confined to the sera of patients with rheumatoid arthritis (RA) and not found in other seronegative arthritides. High levels were found in both seropositive and seronegative (as judged by latex slide and sheep cell differential agglutination for IgM antiglobulins) patients with RA and were associated with systemic disease but not synovitis. Very high levels (more than twice the upper limit of normal) showed a strong association with vasculitis.     

IgM, IgG and IgA rheumatoid factors (antiglobulins) in early rheumatoid arthritis and their production of articular index over one year

An enzyme-linked immunosorbent assay was used to detect antiglobulins (rheumatoid factors, RF) of various classes in 33 patients with recently diagnosed rheumatoid arthritis and to follow their progress with 3-monthly checks for 1 year. For RF, IgA-RF and IgM-RF showed greater sensitivity than the latex test, either or both being positive in 76%. There was no correlation between any of the measures of RF and patient's clinical status as judged by articular index (AI), or serum CRP level. For individual patients, RF levels varied considerably between assessments. The best predictors of clinical status over 1 year were the initial AI and the latex test for RF. While class-specific measurement of RF is more sensitive than the latex test, the variation of individual classes of antiglobulins over time within individual patients makes them less helpful as predictors of disease progress.     

Specificity of IgM antiglobulins produced in rheumatoid arthritis and tropical infections

Summary The measurement of rheumatoid factors is of limited value in West Africa due to the low rheumatoid factor seroprevalence among patients with rheumatoid arthritis and the increased seroprevalence among healthy individuals and those with infectious diseases in the region. Using ELISA methods, we have been able to increase the specificity of rheumatoid factor measurement although the sensitivity of this test remains low. Furthermore, among the infectious diseases studied, there was no preferential binding of rheumatoid factors to the Fab gamma protion of immunoglobulin over the Fc gamma portion.     

Immunoglobulin inclusions in rheumatoid arthritis polymorphonuclear cells: Lack of correlation with circulating immune complexes

Summary A discriminating direct immunofluorescent test has been used to identify immunoglobulin inclusions in polymorphonuclear leucocytes (PMNs) isolated from the blood of patients with rheumatoid arthritis. These inclusions are thought to represent phagocytosed immune complexes, since normal PMNs incubated in RA sera known to contain raised levels of immune complexes developed similar immunoglobulin inclusions. Inclusions did not develop in normal PMNs incubated in normal serum.No correlation was found between the percentage of either RA blood PMNs with immunoglobulin inclusions or normal PMNs developing inclusions after incubation in RA sera, and levels of immune complexes in the corresponding sera.Using heat-aggregated IgG as a laboratory model of immune complexes, a simple relationship has been demonstrated between the uptake of IgG aggregates by normal PMNs and the concentrations of IgG aggregates in the test solutions over a concentration range of 12.5–200 g ml^–1.These results indicate that the C1q- PEG test gives no measure of the actual amounts of immune complexes available in serum for phagocytosis.     

IgE and IgE-rheumatoid factors in circulating immune complexes in rheumatoid arthritis.

The sera of 21 patients with rheumatoid arthritis (RA), 11 patients with systemic lupus erythematosus (SLE), and 20 healthy subjects were analysed for the presence of IgE in immune complex fractions. These fractions were isolated by polyethylene glycol precipitation and gel filtration. Thirteen sera from RA patients contained IgE immune complexes (IC) and 11 of these were from patients with extra-articular manifestations. One SLE and none of the control sera contained such material. The serum IgE level did not correlate with IgE content of the IC fractions. Higher mean serum IgE levels were found in RA patients with extra-articular complications than in controls or RA patients with joint disease only, but the differences did not reach statistical significance. IgE anti-rabbit IgG (IgE rheumatoid factors) could be demonstrated in some IgE positive IC fractions. Antibodies to IgE, in 2 instances characterised as belonging to IgG class, were also found in ICs. This suggests the presence of anti IgE complexes. It is suggested that IgE, including some with rheumatoid factor activity, is contained in complexes which may be involved in some extra-articular manifestations of RA.     

IgE rheumatoid factor. Occurrence and diagnostic importance in comparison with IgM rheumatoid factor and circulating immune complexes.

The sera of 80 patients suffering from rheumatoid arthritis (RA)--30 of them with extraarticular manifestations (EAM) and 50 patients with articular disease only--of 25 patients with other joint diseases and of 30 normal healthy subjects, were analyzed for the presence of 1) IgE rheumatoid factors (IgE RF) by means of a solid phase radioimmunoassay and an ELISA, 2) IgM rheumatoid factors by using solid phase radioimmune techniques, and 3) circulating immune complexes (CIC) with the C1q binding test (C1q BT) and the solid phase conglutinin binding test (SPCBT). The best technique to discriminate RA patients with EAM from RA patients without EAM and patients with other articular diseases was the determination of IgE RF (73.3%, 38.0%, 0%, resp.) compared to IgM RF (86.7%, 78.0%, and 56.0%) and CIC (C1q BT: 80.0%, 66.0% and 45.0%; SPCBT: 46.7%, 22.0%, and 20.0%). The results suggest a certain role of IgE RF for diagnosis and a possible development of extraarticular manifestations in rheumatoid arthritis.     

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)     

Immunisation of guinea-pigs with circulating immune complexes from patients with rheumatoid arthritis.

Sixteen guinea-pigs were immunised with immune complexes isolated from serum of nine patients with rheumatoid arthritis. The resulting antisera were analysed by radioimmunoassays. All guinea-pig sera were extensively absorbed with normal human serum. After this absorption eight guinea-pig sera contained antibodies specific for immune complexes isolated from the sera of three patients. One of these antisera reacted not only with immune complexes (and serum) from the corresponding patient but also with immune complexes (and sera) from other patients with rheumatoid arthritis. The antigen(s) to which the guinea-pig antibodies were directed sedimented as IgM, and they bound to IgG Sepharose. Therefore the guinea-pig sera were absorbed with IgM-rheumatoid factors isolated from the serum of the corresponding patient. After this absorption, the guinea-pig sera had lost their reactivity with immune complexes. We conclude that these antisera did not detect an exogenous antigen in immune complexes from patients with rheumatoid arthritis. The positive reactions found were due to antibodies specific for (idiotypic?) antigenic determinants on IgM-rheumatoid factors.     

Effect of penicillamine therapy on circulating immune complexes in rheumatoid arthritis

Mohammed, I., Barraclough, D., Holborow, E. J., and Ansell, B. M. (1976).Annals of the Rheumatic Diseases, 35, 458-462. Effect of penicillamine therapy on circulating immune complexes in rheumatoid arthritis. The sera of 40 patients with severe progressive rheumatoid arthritis were examined for the presence of soluble immune complexes before penicillamine therapy was started, and again after treatment for a mean period of 14·4 months. The methods used were radiobioassay (macrophage uptake), Clq-binding capacity, and precipitation by 4% polyethylene glycol.

Before treatment the sera of 37 patients showed significantly enhanced uptake of ¹²⁵I-labelled aggregated human IgG by guinea pig macrophages. Treatment produced significant falls in mean erythrocyte sedimentation rate, differential agglutination titre, and serum IgG and IgM levels, and enhancing complexes (EC) decreased or disappeared in 20 patients. In 9 patients EC changed to inhibiting complexes, and in 8 EC levels were unchanged. In 6 of 8 patients with cutaneous vasculitis initially, both lesions and EC disappeared. The total protein and the IgG and IgM precipitated from patients' sera by 4% polyethylene glycol fell significantly on treatment. Antinuclear antibody titres were unchanged by penicillamine, and 3 patients acquired these antibodies during treatment.

These findings suggest that penicillamine treatment in rheumatoid arthritis reduces the level of circulating soluble immune complexes in which IgM rheumatoid factor is a component.

     

Effect of antimalarial treatment on circulating immune complexes in rheumatoid arthritis

The relationship between the effect of chloroquine treatment on circulating immune complexes in patients with rheumatoid arthritis (RA) was determined by the 125I Clq binding assay. Three groups were studied: (a) 20 patients treated daily for 6 months with chloroquine sulphate 250 mg plus prednisone 7.5 mg and nonsteroidal antiinflammatory drugs (NSAID); (b) 20 patients not taking antimalarials but treated with prednisone and NSAID; (c) 41 controls. Results suggest that chloroquine sulphate therapy induced a marked decrease of immune complexes in patients with RA, an effect not observed with treatment by prednisone and NSAID only.     

Characterisation of the size and composition of circulating immune complexes in patients with rheumatoid arthritis.

The size and composition of circulating immune complexes in the sera of patients with rheumatoid arthritis (RA) were studied in relation to different manifestations of the disease. Circulating immune complexes from the sera of 94 patients (50 with extra-articular disease) and 10 matched controls were fractionated by sucrose density gradient ultracentrifugation. The composition, immunoglobulin and rheumatoid factor (RF) concentrations within each of the fractions were determined by a sensitive enzyme linked immunosorbent assay (ELISA). Intermediate size (14S-21S) IgG complexes containing RF activity and 22S IgG-IgM RF complexes were found in the sera of 40 patients with RA, while intermediate size complexes of self associated IgG RF and larger size complexes (greater than 22S) of IgG RF and IgM RF were associated with extra-articular features of RA (50% of extra-articular disease). Complexes containing IgA were found in the sera of many patients with RA, and dimeric IgA RF mainly in patients with extra-articular disease. These results support the view that whereas small size circulating immune complexes are of no primary pathogenic importance in synovitis, large size (greater than 22S) circulating immune complexes may play a role in extra-articular disease in RA. Current understanding of the formation of large complexes provides a biological explanation for their occurrence and effects.     

Synthesis of IgM, IgG and IgA in rheumatoid arthritis.

We studied the production of immunoglobulins by lymphocytes separated from the blood of 15 rheumatoid arthritis (RA) patients, of 12 patients suffering from other connective tissue diseases (CTD), and of 18 healthy controls. The production of IgM, IgG and IgA in pokeweed-mitogen-stimulated cultures was measured by counting the number of plaque-forming cells (PFC) and by determining the concentration of secreted immunoglobulins by means of an enzyme immunoassay. Synthesis of immunoglobulins, particularly IgM and IgG, was lower than in other CTD patients or controls. The IgM response of RA patients was 20% and 29% (PFC and Ig concentrations) that of the controls. The respective figures for IgG were 33% and 53% and for IgA 61% and 72%.     

Cutaneous vascular immunofluorescence in rheumatoid arthritis: Correlation with circulating immune complexes and vasculitis

The presence of immunoglobulin and complement in the cutaneous blood vessels of clinically uninvolved forearm skin was studied in 70 patients with rheumatoid arthritis, using immunofluorescent techniques. Patients with evidence of these immune deposits had a greater prevalence of circulating immune complexes, vasculitic skin lesions, subcutaneous nodules, high titer rheumatoid factor and other findings suggestive of active vasculitis. Biopsy of uninvolved forearm skin may be a useful tool in assessing those patients with rheumatoid arthritis suspected of having a systemic vasculitis.     

The frequency of circulating immune complexes in rheumatoid arthritis and systemic lupus erythematosus

Summary Sera from patients with rheumatoid arthritis and systemic lupus erythematosus have been examined for the presence of complement-fixing immune complexes using three assays, (a) a fluid phase Clq binding assay, (b) a solid phase Clq binding assay and (c) the Raji cell assay.By simultaneously screening all the sera within each disease group we established that circulating immune complexes frequently occur but that there is a discordance between the assays, even between the two assays involving binding to Clq. Distinct clinical profiles emerged with the fluid phase Clq binding assay being most frequently positive in sera from patients with extra-articular rheumatoid arthritis. The solid phase Clq binding assay and the Raji cell assay were more frequently positive in sera from patients with systemic lupus erythematosus. The prevalence of circulating immune complexes and the comparative performance of the three assays in each disease is examined in detail.     

Demonstration of an unidentified 48 kD polypeptide in circulating immune complexes in rheumatoid arthritis.

Circulating immune complexes (CIC) were isolated from 25 patients with rheumatoid arthritis (RA) by anti-C1q affinity chromatography. The components were detected by silver stained sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels and identified by the Western blot. The CIC were composed of 20 different polypeptides, including albumin, immunoglobulin, complement, and acute phase reactants. Two components (molecular weight 48 kD and 45 kD respectively) remained unidentified. The 48 kD polypeptide was found in CIC from six out of 14 patients (43%) with extra-articular RA, but from none of eight patients with vasculitic complications of other connective tissue diseases. All immunoreactants were more frequently found in the patients with extra-articular features of RA. Although these results emphasise that most CIC in RA are composed of endogenous proteins, the 48 kD polypeptide is a candidate for an extrinsic antigen in RA.     

Complement-activating properties of immune complexes are suppressed by IgM rheumatoid factor and enhanced by IgG rheumatoid factor

Summary The effect of rheumatoid factor (RF) on complement-activating capacity of aggregated IgG was investigated. The degree of complement activation induced by the addition of specific amounts of aggregated IgG to patients' sera and normal sera was demonstrated by the inhibition of hemolytic activity (%IHA). The %IHA was significantly lower in rheumatoid arthritis (RA) sera and higher in systemic lupus erythematosus (SLE) sera, compared with normal sera. There was a negative correlation between %IHA and IgMRF/IgGRF ratio in RA and SLE sera, and RA synovial fluid. The %IHA and IgGRF were positively correlated in RA sera. The IgMRF/IgGRF ratio was significantly lower in SLE sera than in RA sera and systemic sclerosis sera, and was significantly lower in RA synovial fluid than in osteoarthritis synovial fluid.Isolated RF, consisting of mostly IgMRF class, inhibited complement-activating properties of aggregated IgG, depending on the concentration of RF. Isolated RF was further purified by the fractionation using high pressure liquid chromatography, and IgGRF and IgMRF were obtained. IgMRF significantly suppressed the complement-activating capacity of aggregated IgG, whereas IgGRF promoted it. These observations suggest that IgMRF acts protectively, while IgGRF induces inflammation.Thus, the expression of the biological activity of RF with special reference to immune complex interaction mainly depends on the IgMRF/IgGRF ratio.