Detection of DNA Autoantibodies by Electrophoretic Mobility Shift Assay

Although the presence of antibodies against double-stranded (ds) DNA is considered the serological hallmark of systemic lupus erythematosus (SLE), it is not detected in all SLE patients by routine laboratory tests. Looking at DNA-anti(ds)DNA interaction as one kind of DNA-protein interaction gave us the grounds for a novel type of assay, easy to perform, and providing a direct insight on DNA-anti(ds)DNA IgG interaction. The assay is an application of the electrophoretic mobility shift assay (EMSA) and is based on the observation that the electrophoretic mobility of a DNA-protein complex is typically less than that of free DNA. The EMSA, performed here with purified bacterial DNA and the purified IgG fraction of sera from systemic lupus erythematosus (SLE) or other patients as well as from healthy individuals, revealed itself to be more sensitive than the routinely used assays for the detection of anti-dsDNA in SLE and discoid lupus erythematosus (DLE) patients. In addition, besides providing a direct visualization of DNA-anti(ds)DNA IgG complexes, the assay offers the possibility to study in detail the nature of DNA-IgG interactions. In a further development, we showed that the assay could be performed successfully with sera.