Nephritogenic autoantibodies but absence of nephritis in Il-12p35-deficient mice with pristane-induced lupus.

BACKGROUND: There is strong evidence that Th1 cytokines are essential for disease in murine models of lupus. Interleukin-12 (IL-12) is essential for Th1 cell differentiation and induces interferon-gamma (IFN-gamma) production. Paradoxically, it has been suggested that an IL-12 defect drives the pathogenesis of lupus, although its precise role remains unclear. We investigated the role of IL-12 for lupus-like disease induced by pristane. IL-12p35-deficient (-/-) and control (+/+) BALB/c mice were treated with pristane or phosphate-buffered saline (PBS).
METHODS: Proteinuria was measured and renal pathology evaluated 10 months after treatment. Sera were analyzed for autoantibodies and total immunoglobulin levels. Cytokine expression and production was analyzed.
RESULTS: Pristane induced nephritogenic autoantibodies and renal immunoglobulin and complement deposition in both IL-12 -/- and +/+ mice. However, proliferative pathology and proteinuria were absent in IL-12-/- mice, whereas pristane induced severe nephritis in one third of the +/+ mice. As expected, cytokine balance was skewed toward a Th2 response in pristane-treated IL-12 -/- mice.
CONCLUSION: These data indicate that renal immune complex deposition can occur in the absence of IL-12p35, but that structural renal damage requires the presence of IL-12p35 or mediators induced by this molecule, such as IFN-gamma. In contrast to the abrogation of nephritogenic autoantibodies by the lack of IFN-gamma, such antibodies are induced by pristane in IL-12p35-deficient mice. Absence of structural renal disease, despite the presence of nephritogenic autoantibodies in pristane-treated IL-12-/- mice, indicates that antibody deposition alone is not sufficient for the development of lupus nephritis in this model.