Anti-fibronectin autoantibodies in systemic lupus erythematosus, rheumatoid polyarthritis, and various viral or bacterial infectious diseases

A micro-enzyme linked immunosorbent assay (ELISA) aimed at detecting anti-fibronectin (anti-Fn) antibodies has been developed and standardized. Fifty sera from systemic lupus erythematosus (SLE), 50 from rheumatoid arthritis (RA) patients, as well as 200 sera from patients with bacterial or viral infections were assayed for the presence of anti-Fn autoantibodies. The IgG fractions of three representative positive sera (1 SLE, 1 RA and 1 streptococcal endocarditis) were digested with pepsin and the resulting F(ab')2 fragment assayed in the test. The presence of the anti-Fn activity in these fragments as well as lack of correlation in individual sera between the level of anti-Fn (as determined by ELISA) and that of Ig or immune complexes, suggest that our anti-Fn autoantibodies are indeed detected in our assay. The meaning of these antibodies, which were also found with bacterial and viral infections is discussed within the frame of the fibronectin biological properties.