Abstract
A method is described for the in vitro labeling of calf thymus native DNA (nDNA) with 125I. The 125I‐calf thymus nDNA produced by this method is suitable for use in the Millipore filter assay for antibodies to nDNA in sera of patients with systemic lupus erythematosus and gives results equivalent to those obtained with 3H‐HeLa cell nDNA labeled in vivo.