Fibronectin in plasma and synovial fluid of patients with rheumatic diseases.

Fibronectin is a high molecular weight glycoprotein from plasma and other body fluids, connective tissue matrix and basement membranes. No significant differences in the mean values of plasma fibronectin were found in patients with rheumatic diseases compared to control subjects. The fibronectin in synovial fluids in these patients presented higher levels than in plasma. No other protein from the synovial fluid presented such a peculiar behaviour. The synovial fluid fibronectin/plasma fibronectin ratio is 2.49 in patients with rheumatoid arthritis, 1.56 in those with inflammatory nonrheumatoid arthritides and 1.60 in those with osteoarthritis. Statistically significant higher values of synovial fibronectin were found in patients with rheumatoid arthritis compared to those with osteoarthritis. No significant statistical correlations were found between the synovial fibronectin concentrations and the other clinical or biological parameters of the rheumatoid arthritis patients, but for synovial fluid C3. Immunohistochemical localization of fibronectin in the rheumatoid synovium showed more intense and extended specific deposits than in the control patients. These results suggest a local synthesis of fibronectin related to the chronic inflammatory process.