Immunofluorescent demonstration of an IgG-B1C complex in synovial lining cells of rheumatoid synovial membrane.

Synovial tissues obtained at arthrotomy or by needle biopsy were digested with trypsin, and suspensions of synovial cells isolated. Immunofluorescent staining of these cells has shown the simultaneous presence of immunoglobulin G (IgG) and the β component of complement in the cytoplasm of most of the phagocytic lining cells of fifteen of seventeen synovia obtained from both seropositive and seronegative patients with rheumatoid arthritis. This staining pattern was not found in synovial cells obtained from patients with other inflammatory or non-inflammatory arthritides. Discrete cytoplasmic inclusions composed of: (1) IgG and α, and (2) IgG and rheumatoid factor were also observed, but only in synovial cells from seropositive rheumatoid patients. The significance of the presence of an apparent IgG–β complex in the synovial lining cells of most patients with rheumatoid arthritis is discussed.