The common occurrence of internal image type anti-idiotypic antibodies in rabbits immunized with monoclonal and polyclonal human IgM rheumatoid factors.

We have previously reported that rabbits immunized with a polyclonal human rheumatoid factor (RF) autoantibody preparation could induce anti-idiotypic antibodies bearing the 'internal image' of the Fc fragments of human IgG. The 'internal image' anti-idiotype have been shown to react with both the RF molecules as well as with the RF receptors on B lymphocytes. Under what conditions these anti-idiotypes occur is not known. Presently, we report that these anti-idiotypic antibodies occur more frequently than previously thought and could be isolated in sera of rabbits immunized with either monoclonal paraproteins with RF activity or other purified human polyclonal serum RFs. Immunization of rabbits with a peptide corresponding to the second complementarity-determining regions of a monoclonal RF did not induce this anti-idiotype. Immunization of goats with human RF similarly did not result in induction of such anti-idiotype. Induction of these anti-idiotypes thus depended upon immunization with the intact RF antigen as well as the species of animal immunized. The repeated isolation of 'internal image' anti-idiotypic antibodies from RF immunized rabbits suggests that the antigenic conformations recognized by human RF autoantibodies are restricted, and that 'internal image' anti-idiotypic species to RF may pre-exist within the rabbit immune network. Such broadly cross-reactive anti-idiotypic reagents provide unique reagents for studying the regulation of RF autoantibody synthesis.