Distribution of an anti-DNA idiotype among autoantibodies in patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA).

Autoantibodies from patients with systemic lupus erythematosus, rheumatoid arthritis, or other connective tissue disorders were probed for the presence of a cross-reactive idiotype (AM Id) originally defined on human anti-double-stranded DNA antibodies. The AM Id was distributed primarily among antibodies to double-stranded DNA, single-stranded DNA, or cardiolipin in patients with systemic lupus erythematosus and antibodies to single-stranded DNA or cardiolipin and rheumatoid factor in patients with rheumatoid arthritis, thus tending to codistribute with the predominant primary autoantibodies in both diseases. Strong associations were observed particularly between the AM Id and anti-single-stranded DNA antibodies in patients with systemic lupus erythematosus and the AM Id and anticardiolipin antibodies in patients with rheumatoid arthritis. Affinity absorption experiments with sera from individual lupus patients showed that up to 41% of the anti-single-stranded DNA antibodies were Id positive. The results indicate that the AM Id may be widely distributed among antibodies that have a potential for binding DNA.