Immune complexes in rheumatoid synovitis: a mixed staining immunofluorescence study.

Complexes of IgG—rheumatoid factor (RF) and IgG—β1C were demonstrated in the synovial membrane obtained from patients with rheumatoid arthritis (RA) by a mixed immunofluorescence method that shows simultaneously the two components of the complex. IgG—RF was found only in the synovia of cases with circulating RF, while IgG—β1C deposits could be detected in both seropositive and seronegative cases. These findings are discussed in connection with the pathogenesis of rheumatoid synovitis in the light of the immune complex pathogenetic mechanism.