[Radioimmunological demonstration of DNA-specific antibodies]

Using 125I chemically labelled denatured (d) and native (n) DNA, specifically binding antibodies were demonstrated in the sera of Lupus erythemathodes patients by means of the Farr technique. (NH4)2SO4 was used to separate the immunologically bound 125I-d-DNA. For 125I-n-DNA the use of a secondary antiserum for the precipitation of the primary immune complex is advantageous. The influence of antigen concentration upon the binding rate was studied. Titre determinations can be made with the proposed method.