TLR9 and TLR4 are required for the development of autoimmunity and lupus nephritis in pristane nephropathy

Systemic lupus erythematosus is a common autoimmune disease, with kidney involvement a serious complication associated with poor prognosis. Humoral immune responses constitute the hallmark of disease, however T helper cells are required for the generation of autoantibodies, as well as the induction and progression of renal injury. Administration of pristane to genetically intact mice results in the development of hypergammaglobulinaemia with the production of lupus like autoantibodies and proliferative glomerulonephritis, with similarities to human lupus nephritis. TLRs are intricately linked to the development of autoimmunity and are involved in the development of lupus nephritis. We injected wild type, TLR9-/- and TLR4-/- mice with pristane and assessed cellular and humoral autoimmunity and renal injury, 8 months later. TLR9-/- mice demonstrated a predominant decrease in Th1 cytokine production which resulted in decreased anti-RNP antibody levels, while anti-dsDNA levels remained intact. Compared to wild type mice treated with pristane, functional and histological renal injury and glomerular immunoglobulin and complement deposition was decreased in TLR9-/- mice. TLR4-/- mice demonstrated a global decrease in both Th1, IFNγ, and Th17 associated IL-17A and IL-6 cytokine production. Autoantibody levels of anti-dsDNA and anti-RNP were both decreased. Renal injury was attenuated in TLR4-/- mice which demonstrated less glomerular immunoglobulin and complement deposition. These results demonstrate that both TLR9 and TLR4 are required for 'full-blown' autoimmunity and organ injury in experimental lupus induced by pristane.