TLR9 and systemic lupus erythematosus: SR Christensen et al. revealed contrasting functions of TLR9 and TLR7 in lupus pathogenesis: TLR9 exacerbated autoimmune diseases by activating lymphocytes and plasmacytoid dendritic cells, whereas TLR7 served as a protective factor by reducing disease severity and lymphocyte activation (30).