I FN-γ, a pleiotropic cytokine, is a key effector molecule in the pathogenesis of several autoimmune diseases, including lupus. Importantly, deletion of IFN-γ or IFN-γR in several lupus-predisposed mouse strains resulted in significant disease reduction, suggesting the potential for therapeutic intervention. We evaluated whether intramuscular injections of plasmids with cDNA encoding IFN-γR/Fc can retard lupus development and progression in MRL-Fas^lpr mice. Therapy significantly reduced serum levels of IFN-γ, as well as disease manifestations (autoantibodies, lymphoid hyperplasia, glomerulonephritis, mortality), when treatment was initiated at the predisease stage, particularly when IFN-γR/Fc expression was enhanced by electroporation at the injection site. Remarkably, disease was arrested and even ameliorated when this treatment was initiated at an advanced stage. This therapy represents a rare example of disease reversal and makes application of this nonviral gene therapy in humans with lupus (and perhaps other autoimmune/inflammatory conditions) highly promising.