Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease in which the immune system attacks the patient's tissues, resulting in inflammation and damage (Tan et al., 1982). SLE is associated with the presence of abnormally elevated titers of a variety of antibodies, including antibodies to double-stranded (ds) DNA, in the serum (Egner, 2000). The presence of anti-dsDNA antibodies in abnormal titers has become the serological hallmark of the disease, and it is widely acknowledged that deposition of those autoantibodies in the form of immune complexes incites the inflammation and tissues damage that are characteristics of SLE (Riboldi et al., 2005). Yet the perfect method for detecting anti-dsDNA remains controversial, whether regarding the antigen source or the technique used (Egner, 2000; Riboldi et al., 2005; McCloskey et al., 2010). Here we describe a simplified method for the isolation and purification of DNA associated with the plasma membrane of cultured human lymphocytes (Wil2), hereafter designated 'pmDNA' that is shown, by electrophoretic mobility shift assay (EMSA), to form a complex with IgG isolated from SLE patients' sera but not with IgG isolated from healthy individuals' sera. We also show that Wil2 pmDNA is a choice antigen for the detection of anti-dsDNA in the serum of SLE patients by an indirect immunofluorescence in vivo assay.