Limited anti-DNA antibody specificity in systemic lupus erythematosus

Twenty-one sera from 11 patients with systemic lupus erythematosus were titrated with 125I-ss-calf thymus DNA to determine their maximum capacity to bind DNA. Only five sera were capable of binding greater than 90% of the input DNA. The remaining sixteen sera showed maximum DNA binding levels between 35% and 85%. The inability of these sera to bind all of the input DNA is shown to be dependent on variations in the molecular weight of the DNA antigen. The possibility that these differences in DNA binding reflect differences in antigenic specificity is discussed.