Demonstration of a new antinuclear antibody (anti-RA33) that is highly specific for rheumatoid arthritis.

Using immunoblot analysis with soluble nuclear extracts from HeLa cells, we identified autoantibodies to an antigen with a molecular weight of approximately 33,000 in 36% of 95 sera from rheumatoid arthritis patients, but in only 1 of 170 controls. The antigen, termed RA33, was resistant to DNase and RNase digestion but sensitive to proteinase K treatment. There was no discernible relation to other autoantibodies. Thus, this newly described autoantibody appears to be highly specific for rheumatoid arthritis.