In SLE, intracellular TLR7, TLR8, and TLR9 in plasmacytoid dendritic cells recognize nucleic acids, triggering type I interferon production, a key mediator in SLE pathogenesis characterized by elevated IFN-α levels and an increased expression of interferon-inducible genes. This evidence concerns the gene TLR9 and systemic lupus erythematosus.