Studies of isolated synovial lining cells of rheumatoid and nonrheumatoid synovial membranes

Synovial membranes from patients with rheumatoid arthritis and other arthritides were digested with tryps.n to produce suspensions of synovial cells. The cells were stained by the direct fluorescent antibody technique for IgG, IgM and the β1c (C3) component of complement, using fluorescein and rhodamine isothiocyanate‐labeled antisera. A characteristic diffuse staining pattern for IgG and β1c was observed in the cytoplasm of the phagocytic lining cells of rheumatoid synovium. In seropositive patients, inclusions containing IgG, IgM, and β1c were also stained in these cells. The role of these immunoglobulins, localized in the lining cells, is discussed in relation to rheumatoid inflammation.