Objective. The autoantibody specificities that dominate the deposits in lupus kidneys remain unclear. Reasoning that previously utilized elution buffers such as acidic glycine and ammonium thiocyanate may not have been maximally effective in eluting all Ig deposits from the kidneys, this study was conducted to experiment with a stronger dissociating agent, urea-glycine.Methods. Seven antinuclear antibody-positive, nephritic female (SWR Ű NZB)F 1 (SNF1) lupus mice were selected for the elution study. Deposited Ig was eluted from their kidneys using 3 different elution buffers: 0.15M glycine-HCl buffer, 1.3M ammonia thiocyanate/0.15M glycine-HCl buffer, and 5M urea/ 0.15M glycine-HCl buffer. All eluates were tested for specificity against a variety of nuclear and glomerular antigens.Results. Compared with conventional elution buffers, the urea-based regimen eluted severalfold more IgG and IgM antinuclear antibodies from the kidneys of nephritic SNF1 lupus mice. IgG anti-double-stranded DNA (anti-dsDNA) antibodies were not only the most prevalent species in these renal deposits, they were also heavily enriched in the kidneys, relative to the corresponding serum levels. A substantial fraction of the anti-single-stranded DNA and antihistone/DNA (but not antihistone) reactivity in these eluates was due to cross-reactive anti-dsDNA antibodies. No reactivity with SSA, SSB, Sm, RNP, Jo-1, Scl-70, or ribosomal P antigens could be demonstrated in these eluates. Importantly, the urea-glycine eluates differed from the conventional eluates in having significantly greater reactivity to glomerular substrate and laminin.Conclusion. This novel urea-based elution provides further support for the dominance of antibodies in lupus kidneys, with strong polyreactivity to DNA and glomerular substrate.Antibody-mediated end organ pathology is a cardinal feature of systemic lupus erythematosus. In particular, antinuclear antibodies (ANAs) have been accorded a dominant role in mediating this disease (1-3). Their temporal relationship to the clinical course of the disease and the findings of direct antibody transfer studies in murine models have together indicated their effector role in end organ disease. Although recent genetic studies have shed light on the potential origins of nephrophilic antibodies (4), the antibody specificities that prevail within the end organs, and are responsible for the pathology, remain unclear.One traditional approach to this question has been to simply examine the specificities of the autoantibodies deposited within the kidneys of mice that spontaneously develop lupus. In the MRL/lpr murine lupus model, antibodies specific for double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), nucleosomes, and histones have been eluted from diseased kidneys (5-7). In addition, van Bruggen et al have noted that eluates from MRL/lpr mouse kidneys demonstrated specificity for glomerular and tubular basement membrane antigens (7). Working with the same mouse model, others have observed that the renal eluates from these kidne...