Viral 5′‐triphosphate RNA and non‐CpG DNA aggravate autoimmunity and lupus nephritis <i>via</i> distinct TLR‐independent immune responses

Certain viral nucleic acids aggravate autoimmunity through nucleic acid-specific TLR. Viral 5'-triphosphate RNA (3P-RNA) and double-stranded non-CpG DNA induce antiviral immunity via TLR-independent pathways but their role in autoimmunity is unknown. Transient exposure of 16-wk-old MRL(lpr/lpr) mice to 3P-RNA aggravated lupus nephritis by increasing IFN signaling and decreasing CD4(+)CD25(+) T cells. By contrast, transient exposure to non-CpG DNA exacerbate lupus nephritis in association with splenomegaly, lymphoproliferation, hypergammaglobulinaemia and increased B220(+)CD138(+) plasma cells. Both, 3P-RNA and non-CpG DNA increased glomerular complement factor C3c deposits but both nucleic acid formats were less potent in aggravating renal pathology as compared with CpG DNA. 3P-RNA and non-CpG DNA also localized to the glomerular mesangial cells and activated cultured mesangial cells to produce IL-6. We conclude, 3P-RNA or non-CpG DNA both trigger autoimmune disease in MRL(lpr/lpr) mice by specifically activating adaptive immunity but similarly enhance inflammation on the tissue level.