DO CHICKENS IMMUNIZED WITH BACTERIAL IMMUNOGLOBULIN G-BINDING PROTEINS PRODUCE RHEUMATOID FACTOR-LIKE ANTIBODIES

An association between the production of rheumatoid factor (RF)-like a ntibodies in animals immunized with bacterial immunoglobulin (Ig)G-bin ding proteins has been noted. Three potential explanations have been p roposed: (1) altered host IgG due to binding of the immunogen; (2) B-c ell superantigenic properties of the binding proteins; and (3) idiotyp e-anti-idiotype response leading to an antibody which acts as an antig en mimic. In order to distinguish among these possibilities, it is nec essary to carry out studies in animals whose IgG does not react with t he 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 ap propriate control immunogens. The results of these studies provided ev idence for production of specific antibodies to FcRc in groups of chic kens immunized with either the pure protein or bacteria expressing the protein. No significant association with production of RF-like antibo dies was noted, favouring the altered IgG-binding explanation for the association between RF-like antibodies and immunization with the bacte rial IgG-binding proteins.