Objective: By searching the synovial fluid of patients with rheumatoid arthritis (RA) for antibodies that react to protein antigens in synovial tissue, we sought to identify putative antigens present in RA synovial tissue that might drive the pathologic immune response believed to be responsible for the joint inflammation.
Methods: Synovial tissue was homogenized in sodium dodecyl sulfate polyacrylamide gel buffer, electrophoresed, and analyzed by immunoblotting.
Results: Antibodies from synovial fluids of patients with RA bound to several proteins in rheumatoid synovial tissues, including a series of low (27.5-, 29-, and 30-kd), middle (43- and 53-kd), and high (140-, 164-, and 182-kd) molecular weight proteins. Most of these antigens were also detected in normal synovial tissue, and the high molecular weight proteins were also present in normal dermal, muscle, and liver tissues. The low and middle molecular weight proteins were detected in some, but not all, of the other normal tissues and in Jurkat cell lysates. Antibodies to the low and high series of proteins were present in all rheumatoid synovial fluids tested, but were generally absent from synovial fluids from patients with other arthritic diseases.
Conclusion: These results show that antibodies in synovial fluids consistently react to several proteins in RA and normal synovial tissues. These antigens are possibly the same antigens provoking the T cell response in RA; therefore, understanding the mechanism of the immune response against these proteins will likely lead to important insight into the etiology of RA.