Relationship between IgG complexes and anti-IgG antibodies in rheumatoid arthritis.

SummaryA selective concentration of antibodies to IgG, both IgM and IgG rheumatoid factors and antibodies to the pepsin site of IgG, was demonstrated in eluates of rheumatoid tissues, but not in control tissues. Many eluates with high amounts of IgG complexes lacked free antibodies to IgG, even when these antibodies were present in the serum. This indicated blocking by IgG complexes. Thus IgM rheumatoid factor could evade detection in some “seronegative” patients by fixation to tissue IgG complexes.