IgG anti-IgG antibodies in rheumatoid arthritis and certain other conditions

Enzyme immunoassay of complement-binding rheumatoid factors

We describe an enzyme immunoassay for the determination of complement-binding rheumatoid factors. Polystyrene tubes are coated with heat aggregated human IgG. The rheumatoid factors (RFs) of patients heat inactivated sera are allowed to bind to aggregated IgG and thereafter saturated with fresh human complement. The amount of C3 complement bound is measured by indirect enzyme immunoassay. The levels of complement binding RFs were measured in 30 patients with seropositive rheumatoid arthritis (RA), in 19 patients with systemic lupus erythematosus (SLE), and in 30 healthy control subjects. Compared to the controls high levels of complement-binding RFs were found both in RA and in SLE (P less than 0.0005). The mean level of the complement binding RFs was higher (P less than 0.05) in active than in inactive SLE. Even though the 19 S IgM RF bound complement, in RA no correlation was found between the level of complement binding RFs and Waaler-Rose titre, but the level of complement binding RF correlated with the levels of nonagglutinating IgM RF (r = 0.56, P less than 0.01) and IgG RF (r = 0.70, P less than 0.001) that were obtained by enzyme immunoassay.

Immunologic tests of value in diagnosis. 1. Acute phase reactants and autoantibodies

Acute phase reactants are nonspecific indicators of tissue necrosis and/or inflammation but may be helpful in determining activity of disease. Rheumatoid factor is likewise rather nonspecific, but its presence is helpful in predicting the course, severity, and complications of rheumatoid arthritis. Numerous antinuclear antibodies have been identified in collagen vascular diseases; perhaps the most specific association is between anti-Sm antibody and systemic lupus erythematosus. Anti-smooth-muscle and antimitochondrial antibodies can aid in differential diagnosis of liver disease, while antithyroid antibodies can perform a similar function in diffuse goiter. Anti-parietal-cell and anti-intrinsic-factor antibodies are quite specific for pernicious anemia.

IgG rheumatoid factor. Relationship to seropositive rheumatoid arthritis and absence in seronegative disorders

IgG rheumatoid factor was detected in the sera of the majority of patients with seropositive rheumatoid arthritis. Values suggestive of IgG rheumatoid factor were noted in one-quarter of patients with seronegative inflammatory arthropathies. These determinations were always low and correlated with elevated IgG concentrations, suggesting nonspecific adherence of IgG rather than a true antigen-antibody reaction. In support of this conclusion, nonrheumatoid factor IgG was capable of concentration-dependent nonspecific adsorption to the solid phase. IgG, but not IgM, rheumatoid factor corresponded with disease activity in patients with seropositive rheumatoid arthritis, suggesting that IgG rheumatoid factor may be important in the pathogenesis.

Antigammaglobulin (rheumatoid factor) activity of human IgG subclasses

A sensitive radioimmunoassay has been applied to the study of rheumatoid factor activity of IgM and IgG subclasses in serum and synovial fluid of patients with rheumatoid arthritis. Although rheumatoid factor activity was found in all four subclasses, its distribution was not the same as that of the total subclasses in normal sera. Results are discussed in relation to the possible clinical value of measuring IgG rheumatoid factor in sera and synovial fluids of patients with rheumatoid arthritis.

Estimation of IgG-antiglobulins in sera of patients with rheumatoid arthritis and chronic liver disorders

Antiglobulin factors of the IgG class were measured in human sera by a modified immunoadsorbent-technique involving absorption to and elution from insoluble preparations of horse IgG. 32 mg of horse IgG insolubilized with bisdiazotized benzidine were used for quantitative immunoadsorption of IgG antiglobulins from 100 mul serum. Different IgG-antiglobulin concentrations could be obtained in two control groups differing in age. Elevated IgG-antiglobulins levels were found both in seropositive (mean value 23.21 +/- 7.08 mug/ml serum) and seronegative (mean value 20.06 +/- 8.39 mug/ml serum) RA patients. High values of IgG-antiglobulins were found in chronic liver disorders, particularly in the group of CAH patients (mean value 25.10 +/- 6.1 mug/ml serum).

Igg rheumatoid factor in serum of rheumatoid arthritis patients

The ability of isolated IgG and F(ab)2 fragments to agglutinate IgG-coated latex particles was used as a test of IgG-RF activity. No definite differences could be proved between controls and RF-negative RA patients, whereas the latex titres of IgG and F(ab)2 of sero-positive RA patients were higher. The IgG latex activity was recovered in the fractions between the 19S and 7S after gradient centrifugation of serum or isolated IgG at pH 7.2 and within the 7S fraction after centrifugation at pH 4.1. The dissociated IgG complexes reformed after neutralization, thus indicating a self-association of the IgG molecules.