Comparative Investigation of Protein Concentration in Serum and Synovial Fluid

The authors report a specific immunological quantitative determination of IgG, IgM, IgA, transferrin and α2 microglobulin simultaneously in serum and in synovial fluid. The concentration of the protein fractions was determined by the linear plate immunodiffusion method. The log-normal frequency distribution of the protein levels in serum and in synovial fluid is clearly demonstrated. The authors found an increase of the serum and synovial fluid IgG, IgM and IgA levels in R. A. Furthermore, they investigated the relation between serum and synovial fluid levels for each protein fraction and they confirm that the permeability of the synovial membrane and molecular weight of the protein fraction are important parameters in the quantitative determination of a protein concentration in synovial fluid in non-rheumatoid synovial fluids. The mechanisms by which the synthesis of immunoglobulins in rheumatoid synovia is masked when Ig levels are determined in synovial fluid, receive mention.