The RF antigen

Scandinavian Journal of Immunology, 1985

Specific rabbit aniisera were prepared against nn IgG with a special conform;)tion (IgG spec.) previously detected in some sera from patients with rheumaioid arthritis. The antibodies had no affinity to normal human IgG iind were not anti-idiotypic to human rheumatoid factor. The affinity of IgG spec, to the antibodies could not be explained by an antiglobulin activiiy lo rahbit IgG. The amouni of protein with affinity ui immobiliited specific IgG F(ab'), of the anlibodies was determined in scrum and syntivial fluid from patients with various joint diseases. A relationship between the content of IgG spec, iind ihc diagnosis of seropositive rheumaioid arthriiis was found on aniilysis of serum samples. IgG spec. alsotKCurred in synovial fluid from some individuiils with seropositive rheumatoid arthrilis. Differences in ihe serum content of IgG spec, could not be explained by differences in the normal IgG content. Circular dichroism analysis of isolaled IgG spec, showed that in the region(s) close to lyrosint-residue(s) this polyclonal protein had similiirities to heiit-aggregated IgG.

Journal of Experimental Medicine, 1981

Intermediate complexes, sedimenting between the 6.6S and 19S components of normal serum on sedimentation velocity ultracentrifugation, were first described by Kunkel et al. (1) in the serum of some patients with rheumatoid arthritis. These complexes consisted of IgG (1, 2) and had rheumatoid factor activity (2). In addition, intermediate-and faster-sedimenting complexes were identified in the synovial fluid of some patients with rheumatoid arthritis (3, 4). Previous work from this laboratory using sedimentation equilibrium ultracentrifugation (5, 6) demonstrated that the intermediate complexes isolated from the plasma of three patients with rheumatoid arthritis were composed of self-associated IgG rheumatoid factor (IgG-RF)J Dimers of self-associated IgG-RF were observed that underwent concentration-dependent polymerization. A model was proposed for self-association that accounted for the stability of dimers by the formation of two antigen-antibody bonds between two IgG-RF molecules. The association constant for dimer formation was not experimentally determined, but was calculated (101° liter/mol) as the square of the measured association constant of each individual bond formed between the F(ab')2 fragment of IgG-RF and normal IgG, which was ~10 5 liter/mol. Undoubtedly, the calculated value would be too high because of energy required for ring closure. The polymerization of dimers to higher molecular forms had an association constant also on the order of 10 5 liter/mol. This report describes studies on the number, location, and other characteristics of the antigenic determinants for the self-association of IgG-RF using the IgG-RF isolated from one patient with rheumatoid arthritis as a model system.

The Journal of Immunology

To localize regions on IgG bound by rheumatoid factors (RF), we studied IgM RF binding to chimeric IgG antibodies consisting of murine V regions fused to human constant regions. Using a modified RF ELISA, we showed that polyclonal RF from rheumatoid arthritis patients bound IgG1, 2, and 4 strongly; IgG3 was also bound, although less well. The majority of 18 monoclonal RF from patients with Waldenstrom's macroglobulinemia bound IgG1, 2, and 4 only. In contrast to RF from RA, 14 of 18 monoclonal RF did not react with IgG3. Only 3 of 18 monoclonal RF bound IgG3 well. By shuffling C region domains between IgG3 and IgG4, we showed that sequence variation in the CH3 domain is responsible for the differential binding of monoclonal RF to IgG3 and IgG4. Hybrid IgG3/IgG4 antibodies containing the CH3 domain of IgG4 were bound by monoclonal RF, whereas those containing the CH3 domain of IgG3 were not. To evaluate the contribution of the N-linked carbohydrate moiety at Asn-297 to RF binding...

Annals of the New York Academy of Sciences, 1975

Arthritis and Rheumatism, 1984

Clonally restricted anti-IgG antibodies were detected, by isoelectric focusing (IEF) and chromatofocusing techniques, in the sera of patients with rheumatoid arthritis (RA). Anti-Fab antibodies were predominantly acidic proteins with isoelectric points of 4.5–6.5 and displayed restricted spectrotype patterns. Proteins reactive with the Fc portion of IgG showed polyclonal spectrotype patterns with alkaline pI of 7.5–9.0. A limited array of anti-Fab spectrotypes was consistently detected in RA sera when analyzed by IEF on 6M urea gels. Additional anti-Fab antibody bands were detected when the RA sera were dialyzed against 4–6M urea prior to IEF analysis, indicating that some anti-Fab antibodies exist in a complexed form in serum. Under these dissociating conditions, anti-Fab antibodies could also be detected in normal subjects, but the spectrotype patterns were more restricted than those in RA sera. Because anti-Fab antibodies may regulate normal immune responses, the increased quantity of clonally restricted anti-Fab antibodies in RA may indicate an abnormality of this immunoregulation.

Annals of the Rheumatic Diseases, 1974

Usual techniques for the detection of antigammaglobulin factors (DAT, SCAT, HEAT, Latex FII) are based upon agglutination reactions and are therefore useful when IgM antibodies are involved. It is well known that antiglobulins also belong to IgG and IgA classes. In our experience, 50 per cent. of patients with JRA are persistently seronegative when sera are tested only with conventional agglutination techniques (Garcia Morteo, Hubscher, and Arana, 1970). Recent papers reported elevated IgG antiglobulins in seronegative RA and JRA demonstrated by means of immunoadsorption techniques employing human, horse, and rabbit gammaglobulin rendered insoluble either with glutaraldehyde or with bisdiazobenzidine. These adsorbents had non-specific elution of immunoglobulins (

Scandinavian Journal of Immunology, 1974

Rheumatoid anti-Gm(a) antibodies were sbown to react with native Gm(a-) IgG. This reaction takes place with tbe C||3 domain (pFc' fragment) of IgG and is not due to anti-isotype specificities contaminating the test system. The reactivity of the Gm(a-) IgG is greatly increased by heat aggregation, and this increase is clearly related to the amount of aggregates formed. Rheumatoid anti-Gm{a) reacts with aggregated IgGi, lgG2. and IgG3 Gm(g+) proteins but not with IgG3 Gm(b+) or IgG4 proteins. Thus there is a clear specificity in the reactions with aggregated IgG of different subclasses. Quantitative hemagglutination inhibition studies in the AutoAnalyzer suggested that the antigenic determinants of native and aggregated Gm(a-i-) or Gm(a-) IgG involved in the reaction with rheumatoid anti-Gm(a) were very similar. Furthermore, immunosorbent studies showed that the same population of rheumatoid anti-Gm(a) antibodies is reacting with the native and aggregated Gm(a+) and Gm(a-) IgG. Analogous findings were obtained using rheumatoid anti-Gm(b') and anti-Gm(g).

Annals of The Rheumatic Diseases, 1981

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.

Molecular Immunology, 1975

A haemagglutination-inhibition assay for studying the interaction of rheumatoid factor with monomeric human IgG has been developed. The indicator system employed consists of sheep red blood ceils actively sensitized with baboon (Papio cynocephalus) IgG. Studies revealed that sub-classes 1, 2 and 4 of human IgG were capable of inhibiting the agglutination of baboon IgG-sensitized sheep red blood cells by rheumatoid arthritic sera, irrespective of Gm phenotype or the anti-Gm specificity of the rheumatoid arthritic sera employed. The pFc', F(ab')z and Fab fragments from pooled human IgG lailed to inhibit the reaction, in contrast to the Fc fragment. The agglutination titres of a panel of rheumatoid arthritic sera from baboon IgG-sensitized sheep red blood cells were compared with their titres in a conventional Rose-Waaler system (i.e. rabbit IgG-sensitized sheep red blood cells). Such a comparison revealed a close similarity in the titres recorded for each serum examined irrespective of the assay system employed. The significance of these findings is discussed.

Journal of Autoimmunity, 1998

Rheumatoid factors (RF) are autoantibodies with specificity for the constant regions of IgG molecules. They are found in several immunopathological diseases. The mechanism(s) by which these autoantibodies are produced is largely unknown. We have previously shown that a single injection of RF-like immune complexes (ICs) into mice selectively induced an intense IgG1antibody production with RF activity. This response was sustained for several months and did not resemble a conventional immune response to an antigen or other immune complexes. In the present study, we sought to elucidate the mechanism for the IgG1 RF response to RF-like ICs. Therefore, the roles of CD4 + T cells, complement and Fc receptors were analysed. In order to characterize the role of CD4 + T cells, RF-like induced IgG1-RF production was analysed in NZB mice treated with a monoclonal antibody (mAb) against the CD4 molecule, which resulted in complete abrogation of IgG1 RF production. To evaluate the importance of Fc Rs, the effect of RF-like ICs was tested in mice deficient for RF RI/III. A significant decrease in the numbers of IgG1 antibody secreting cells, as well as in serum IgG1 RF levels, was found in the deficient mice, as compared with their normal outbred littermates. The role of complement in RF-like ICs mediated IgG1 RF was tested in complement depleted NZB mice, using Cobra venom factor. The IgG1 RF response in complement depleted and intact mice was comparable. Thus, our results demonstrate that RF-like immune complexes selectively induce an Fc R-dependent, complement independent antibody response in mice.