An idiotypic complementarity between rheumatoid factor and anti-peptidoglycan antibodies?

Groups of BALB/c mice have been repeatedly immunized with sterile affinity-purified human rheumatoid factor (RF) preparations from high-titred seropositive rheumatoid arthritis sera. In all cases, there was an antibody response reactive with Streptococcus pyogenes cell wall peptidoglycan-polysaccharide (PG-PS) polymer in both immunodiffusion and ELISA. This antibody could be absorbed by either excess RF or PG-PS, but not by isolated human non-RF IgG or IgM preparations. Groups of mice similarly immunized with non-RF IgG or IgM produced no significant anti-PG-PS antibody response compared with pre-immune sera. All immunogens lacked detectable PG-PS. Thus, anti-PG-PS antibody may be produced by RF immunization in the absence of PG-PS. This suggests some idiotypic complementarity between RF and anti-PG-PS antibodies.