The Rheumatoid Factor in Serum and Synovial Fluid ¶

The agglutination of sensitized sheep cells by a factor in the serum of individuals with rheumatoid arthritis has been the subject of continued investigation since its recognition by Waaler.' This reaction, with its modifications, furnishes the useful diagnostic tests for the illness.1 2, 4, 9, The hemagglutination reaction has also been used in the study of the pathogenesis of rheumatoid arthritis. In this connection, efforts were made to absorb the factor from serum"' or to identify it with a serum protein fraction by virtue of differential solubility5"0" or rate of migration.6'7 These procedures have not been of significant help in the chemical identification of the rheumatoid factor. Rheumatoid arthritis is characterized clinically by the prominence of changes in the synovial tissue and sometimes by the accumulation of joint fluid. Therefore, it was decided to investigate synovial fluid with the thought in mind that the joint itself might be the site of formation of the rheumatoid factor or at least a source of this material which is ultimately found circulating in the blood stream. Since the presence of mucin represents a significant difference between synovial fluid and serum, attention was also focused upon it. The viscosity, mucin clot, and mucin nitrogen to glucosamine ratio determinations reported by Ropes and Bauer8 indicate that the hyaluronic acid of synovial fluid is depolymerized, or incompletely polymerized, in rheumatoid arthritis.