Serum responses in rheumatoid arthritis

SENSITIZATION TO DENATURED AUTOLOGOUS GAMMA GLOBULIN

Immunization of guinea pigs with denatured autologous gamma globulin results in the development of delayed hypersensitivity to some form of gamma globulin. When the autologous gamma globulin is subjected to denaturation with alkaline treatment as employed in this study, guinea pigs regularly develop reactivity to the immunizing material and occasionally to some form of heterologous gamma globulin. With other forms of denaturation, such as produced by urea, ultrasound, or heat, guinea pigs rarely develop sensitivity to the immunizing material but frequently exhibit delayed reactivity to native or denatured heterologous gamma globulin. Reactivity against native autologous gamma globulin does not occur. Guinea pigs immunized with undenatured autologous gamma globulin fail to develop reactivity to any form of gamma globulin. Rabbits immunized with denatured autologous gamma globulin develop circulating antibodies against some form of gamma globulin. Rabbits immunized with alkaline denatured autologous gamma globulin develop antibodies against the preparation used for immunization and against heterologous gamma globulin; rabbits immunized with autologous gamma globulin subjected to freeze-thaw or heat denaturation develop antibodies against heterologous globulin, but antibodies against the immunizing material can only rarely be demonstrated.

Specificity of the reaction between rheumatoid factors and gamma globulin

Rheumatoid factors in the sera of patients with rheumatoid arthritis appear to be specifically directed against genetically determined "antigens" in human γ-globulin. At least eight rheumatoid factors of differing specificity exist; usually several are present in combination in the same serum. The different rheumatoid factors can be readily detected through their pattern of reactivity with anti-Rh antibodies from different individuals. Rheumatoid factors in diseases other than rheumatoid arthritis were found to have a more restricted specificity, contrasted to the broader reactivity of the factors in most rheumatoid arthritis sera. A specificity similar to that for incomplete antibodies was not demonstrated for the reaction of rheumatoid factors with aggregated γ-globulin or with γ-globulin to form the "22S complex." In certain instances, using the anti-Rh system, rheumatoid factors were found to react poorly with the patient's own γ-globulin, compared to that of other individuals of different genetic γ-globulin types. These results, as well as additional indirect evidence, indicate that the rheumatoid factors can possess isospecificity. However, a certain degree of autospecificity was also found which was most clearly evident through complex formation with the patients own γ-globulin and in the reaction with aggregates. The relevance of these findings to possible isoantibody as well as autoantibody concepts is discussed.

A comparative study of different methods for measurement of rheumatoid factor in dog serum

An enzyme linked immunosorbent assay (ELISA) technique was developed and compared with two routinely used methods, latex agglutination and Rose-Waaler hemagglutination, for the measurement of Rheumatoid Factor (RF) in dog serum. The frequency of positive samples for IgM-RF was rather low, about 8-12% of the 460 dogs with different rheumatic disorders being classified as positive by these methods. It was further concluded that the latex agglutination test used in this study (Synbiotics CRF Kit) should be performed only on heat inactivated serum (56 degrees C for 30 minutes) thereby significantly reducing the frequency of weak, probably false, positive agglutination reactions. When this was considered, a significant correlation was obtained for the three different techniques for RF estimation in serum from normal control as well as rheumatic diseased dogs.

Rheumatoid factors in subacute bacterial endocarditis and other infectious diseases

Rheumatoid factors (RF) occur during the course of various infections such as leprosy, infective endocarditis, tuberculosis, trypanosomiasis, visceral larva migrans, infectious mononucleosis, influenza A, hepatitis A or cytomegalovirus. When first described it seemed logical to assume that host-self-immunization with autologous immune complexes provided the initial stimulus for RF production. Subsequently extensive characterization of bacterial, parasitic and viral Fc receptors has suggested an alternative explanation for rheumatoid factor associated with infections. It seems possible that patients make an initial immune response to infecting agent Fc receptors and that anti-anti-Fc receptors or anti-idiotypes either then directly stimulate rheumatoid factor production or are themselves rheumatoid factors. Such a hypothesis might also be applied to rheumatoid arthritis itself where either infecting agent or autologous cell Fc receptors could be the initial immunizing epitopes involved in rheumatoid factor production.

Some factors affecting the quantitation of rheumatoid factors by enzyme immunoassay

Some factors affecting the use of enzyme-labelled antibody to human IgM or enzyme-labelled human IgG for the detection and assay of IgM RFs by enzyme immunoassay have been investigated. IgM RF levels, obtained by standard radioimmunoassay techniques, showed a better agreement with those obtained with enzyme-labelled antibody than with enzyme-labelled human IgG. Immuno-adsorption studies using a sheep cell agglutination test (SCAT) confirmed a partial loss of antigenicity of the IgG molecules due to glutaraldehyde treatment, which increased with the length of time of exposure to glutaraldehyde.