Superoxide generation by synovial fluid neutrophils enhanced by immune complexes and suppressed by rheumatoid factor in synovial fluid.

Synovial fluid (SF) from patients with rheumatoid arthritis (RA) enhanced superoxide generation by neutrophils isolated from RA SF, in contrast to SF from patients with osteoarthritis. These superoxide generation-enhancing substances may be intermediate-sized immune complexes and a complement C5-derived fragment. Rheumatoid factor (RF) isolated from RA SF suppressed superoxide generation-enhancing activity of aggregated IgG. Therefore, biologically active RF may block the interaction of the immune complexes with neutrophils accumulating in RA SF, and protect the joint tissue from the effects of oxygen radicals or proteases.