Immunoreactive granulocyte elastase in rheumatoid synovial fluid and membrane

A specific radioimmunoassay (RIA) was utilized to determine granulocyte elastase in the synovial fluid of a series of 45 rheumatoid joints in 39 patients. The average concentration was approximately 340 micrograms/l, exceeding that of the paired serum sample in all but 6 cases. No correlation was noted in synovial fluid between its content of granulocyte elastase and the total number of white blood cells. The concentrations in sera from rheumatoid patients with non-steroidal anti-inflammatory agents and controls were equivalent. Non-inflammatory exudates contained low concentrations of elastase. The immunoreactive granulocyte elastase in rheumatoid synovial fluid was bound to alpha 1-antitrypsin suggesting release of the enzyme in its active form. An uptake of elastase-containing complexes by macrophage-like cells in the synovial membrane was demonstrated by immunohistochemical staining of tissue using antiserum against granulocyte elastase. The concentrations of immunoreactive granulocyte elastase in the free synovial fluid of rheumatoid arthritic joints presumably only faintly reflect the situation concerning the target substrates.