Detection of rheumatoid-like factors in serum of chickens immunized with bacterial immunoglobulin binding proteins

Do chickens immunized with bacterial immunoglobulin G-binding proteins produce rheumatoid factor-like antibodies?

An association between the production of rheumatoid factor (RF)-like antibodies in animals immunized with bacterial immunoglobulin (Ig)G-binding proteins has been noted. Three potential explanations have been proposed: (1) altered host IgG due to binding of the immunogen; (2) B-cell superantigenic properties of the binding proteins; and (3) idiotype-anti-idiotype response leading to an antibody which acts as an antigen mimic. In order to distinguish among these possibilities, it is necessary to carry out studies in animals whose IgG does not react with the IgG-binding protein immunogen. Consequently, we have determined the effects of immunizing chickens with a purified group C streptococcal IgG-binding protein, FcRc, a bacterium expressing this protein, and appropriate control immunogens. The results of these studies provided evidence for production of specific antibodies to FcRc in groups of chickens immunized with either the pure protein or bacteria expressing the protein. No significant association with production of RF-like antibodies was noted, favouring the altered IgG-binding explanation for the association between RF-like antibodies and immunization with the bacterial IgG-binding proteins.

Testing of bovine sera by ELISA for IgG, IgM and IgA rheumatoid factors

Sera from 19 colostrum-deprived calves less than 1 week old, 24 colostrum-supplemented calves less than 1 week old, 36 3-5-month-old calves and 200 females greater than 9 months of age were tested by ELISA for the presence of IgM, IgG and IgA rheumatoid factors (RF). An increasing level of IgM- and IgG-RF with age was found. IgG-RF levels in the colostrum-supplemented calves were significantly higher than in the non-supplemented calves (p < 0.001). Individual IgG-RF values correlated with serum IgG levels, as determined by zinc sulphate turbidity testing (r=0.59, p < 0.01). No IgA-RF was detected. The cross-reactivity of IgM-RF with heterologous IgG was found to be greatest with rabbit IgG, followed by mouse and chicken IgG. The significance of rheumatoid factors in relation to diagnostic testing is discussed.