Cross-reactive idiotypes in anti-DNA antibodies of systemic lupus erythematosus patients.

Cross-reactive idiotypes associated with the combining site of anti-double-stranded DNA antibodies from systemic lupus erythematosus patients were demonstrated by the ability of isologous lupus sera to block functionally the binding of target anti-DNA antibodies to DNA in vitro. A framework idiotype, denoted AM Id, was identified using xenogeneic anti-idiotype antibodies rendered specific by affinity absorptions. The AM Id was found in 85% of patients with systemic lupus erythematosus (n = 63) and correlated positively with anti-DNA antibodies. Analysis of the distribution of the AM Id among individuals showed that, while present in anti-DNA antibodies to varying degrees in individual patients, it was also found in variable amounts on non-DNA-binding immunoglobulins. These results indicate that the AM Id and anti-DNA antibodies represent overlapping populations of immunoglobulins.