DNA-MOBILITY SHIFT ASSAY AND THE DETECTION OF ANTI-DNA IGG IN SYSTEMIC LUPUS-ERYTHEMATOSUS PATIENTS

Although the presence of antibodies against double-stranded (ds) DNA i s highly specific of systemic lupus erythematosus (SLE), it is not det ected in all SLE patients, perhaps due to a lack of sensitivity of the tests routinely used to assay anti-ids) DNA. Looking for an alternati ve assay, this study explored the applicability of a DNA-mobility shif t assay for the detection of anti-(ds) DNA; furthermore, the study com pared the use of Salmonella typhimurium DNA with that of calf thymus D NA in the assay. After electrophoresis, samples containing S, typhimur ium DNA and Ige from SLE sera showed marked alterations in DNA electro phoretic mobility when compared to DNA alone. In our sampling, SLE pat ients who tested negative for anti-(ds) DNA antibodies with routinely used assays such as Crithidia luciliae immunofluorescence test, radioi mmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA), tested positive for anti-(ds) DNA with the DNAmobility shift assay using S. t yphimuriun? DNA. Incubation with Ige from control sera in the same pro portions as above did not affect S. typhimurium DNA electrophoretic mo bility. When S. typhimurium DNA was replaced by calf thymus DNA, the e ffect on the DNA mobility was less pronounced and less reliable. These results indicated that a DNA-mobility shift assay would be a useful a lternative for the unequivocal detection of abnormal titers of anti-(d s) DNA antibodies. Furthermore, data indicated a greater ability of th e Ige from SLE patients to form complexes with S. typhimurium DNA than with calf thymus DNA, suggesting an alternative testing DNA which may lead to a more sensitive anti-(ds) DNA detection. (C) 1998 Elsevier S cience B.V. All rights reserved.