Effect of an exogenous trigger on the pathogenesis of lupus in (NZB x NZW)F1 mice

Objective. This study examined the interactions between exogenous and endogenous factors shaping the phenotype of lupus in autoimmune (NZB X NZW)F-1 mice exposed to pristane, a model environmental trigger. Methods. Frequencies of various autoantibodies in untreated NZB/NZW mice were determined by various means (immunoprecipitation, enzyme-linked immunosorbent assay [ELISA], Crithidia luciliae kinetoplast staining). Pristane or saline was administered intra-peritoneally to 9-12-week-old NZB/NZW mice, followed by serial studies of autoantibodies, total Ig levels (ELISA), and proteinuria (dipstick). Results. Besides antichromatin/DNA responses, NZB/NZW mice spontaneously produced novel autoantibodies against the double-stranded RNA binding protein RNA helicase A (RHA). In contrast, NZB/NZW mice (n = 70) did not produce autoantibodies against the nuclear RNP (nRNP), Sm, Ro, or La antigens. Pristane exposure synergistically activated the production of antichromatin/DNA antibodies and dramatically accelerated renal disease. Production of anti-nRNP/Sm and Su autoantibodies also was induced, indicating that the unresponsiveness of NZB/NZW mice to these antigens can be overcome. Curiously, pristane treatment did not enhance the production of anti-RHA, suggesting that these autoantibodies are regulated differently than anti-DNA/chromatin and Sm. In contrast to previous reports that suggest a critical role of deficient interleukin-12 (IL-12) production in the pathogenesis of lupus, there was overproduction of IL-12 in the peritoneal cavity of pristane-treated NZB/NZW mice, and their spleen cells also produced large amounts of IL-12. Conclusion. These data lead us to propose that environmental influences exacerbate autoimmune manifestations in genetically lupus-susceptible mice through their stimulatory effects on proinflammatory cytokines, such as IL-12.