High levels of a common anti-DNA idiotype (16/6), a genetic marker for SLE.

Six out of 8 healthy first-degree relatives of a patient with systemic lupus erythematosus (SLE) had very high serum levels of a common anti-DNA idiotype (16/6). In this family an additional sister developed SLE, and all members were heterozygous for C4 deficiency. Measurements of common autoantibody idiotypes may contribute to the understanding of the genetics of autoimmune diseases. They might be found useful in detecting healthy subjects prone to the development of an overt clinical state.