The antibody against the proteoglycan antigen of human articular cartilage was measured by the enzyme-linked immunosorbent technique in sera from 33 patients with rheumatoid arthritis, 12 patients with osteoarthritis and 43 normal donors. High titers of an anti- proteoglycan antibody were encountered frequently in sera of rheumatoid arthritis patients as well as of those with osteoarthritis. In patients with rheumatoid arthritis, however, no relation could be established between the titer of the anti-proteoglycan antibody and disease features such as duration of disease, stage, laboratory tests or rheumatoid serology. The titer was found to be in parallel with that of anti-collagen type II. The results suggest that the production of anti-proteoglycan antibody is not responsible for the pathogenesis of rheumatoid arthritis but is presumably a consequence of the inflammatory and degenerative process in joints.
