Proteinase inhibitors in rheumatoid arthritis.

The concentrations of five normally occurring protease inhibitors in serum and synovial fluid were compared in patients with rheumatoid arthritis, osteoarthrosis, and normal controls. The patients with rheumatoid arthritis showed a significant rise in alpha1-antitrypsin, alpha1-antichymotrypsin, and inter-alpha-trypsin inhibitor (in decreasing order) in serum as well as in synovial fluid. In synovial fluid the inhibitors were present in their native form and bound to hyaluronate. A large molecular protein with immunological specificity of alpha1-antitrypsin, presumably a complex of alpha1-antitrypsin and a protease, could be shown in synovial fluid of all patients with classical and probable rheumatoid arthritis and not in that of the other subjects studied.23Author