Antigenicity of proteins from cultured synovial fibroblasts.

We were able to characterize about 25 antigenic proteins of cultured synovial fibroblasts with apparent molecular weights of 15-230 kd by SDS-electrophoresis and immunoblotting using guinea pig antiserum. Some of these proteins were bovine-serum-derived, adsorbed onto fibroblasts from culture medium. Both rheumatoid and normal sera contained natural antibodies reacting with synovial fibroblast as well as bovine serum antigens when studied with immunoblotting. The amounts of antibodies were quantitated with enzyme immunoassay, measuring IgG and IgA class antibodies against plasma membrane preparations of rheumatoid and normal synovial fibroblasts. No rheumatoid arthritis-related changes were detected in synovial fibroblast protein antigens or antibodies against them in rheumatoid patient specimens.