Objective. The detection of high titers of antibodies against small nuclear ribonucleoproteins (snRNP) is a diagnostic finding in patients in whom systemic lupus erythematosus (SLE) is suspected. Endogenous RNA molecules within snRNP trigger Toll-like receptor 7 (TLR-7) activation in B cells and dendritic cells, leading to anti-snRNP antibody production, which is associated with the development of immune complex nephritis in SLE. The purpose of this study was to investigate the role of TLR-7 in anti-snRNP antibody production and renal disease in SLE induced by an exogenous factor in the absence of genetic predisposition, using the pristane-induced murine lupus model.Methods. Serum autoantibodies, IgG isotypes, and cytokine levels in pristane-treated wild-type and TLR-7-deficient mice were analyzed by enzyme-linked immunosorbent assay. Histopathologic changes in mouse kidneys were determined by light immunofluorescence microscopy. Cell subsets in splenocytes and peritoneal lavage cells from the mice were examined by flow cytometry.Results. We found that anti-snRNP antibody production induced by pristane treatment was entirely dependent on the expression of TLR-7, whereas antidouble-stranded DNA antibody production was not affected by a lack of TLR-7. Impaired anti-snRNP antibody production in TLR-7-deficient mice was paralleled by lower levels of glomerular IgG and complement deposits, as well as less severe glomerulonephritis.Conclusion. TLR-7 is specifically required for the production of RNA-reactive autoantibodies and the development of glomerulonephritis in pristane-induced murine lupus, a model of environmentally triggered SLE in the absence of genetic susceptibility to autoimmunity. Specific interference with TLR-7 activation by endogenous TLR-7 ligands may therefore be a promising novel strategy for the treatment of SLE.The immunologic hallmark of systemic lupus erythematosus (SLE) is the presence of high levels of circulating antinuclear autoantibodies, which develop several years before manifestation of the disease and which are thought to be critically involved in its pathogenesis (1). Recent data indicate that Toll-like receptors (TLRs) recognizing self nucleic acids may be critically involved in breaking peripheral tolerance against nuclear antigens and allowing the generation of a destructive autoimmune response in SLE. By activating Tolllike receptor 9 (TLR-9) and TLR-7/8, endogenous DNA and RNA sequences contained within nuclear autoantigens in circulating autoimmune complexes act as "autoadjuvants" for efficient priming and boosting of the autoimmune response in SLE (2). By simultaneous