In the periphery, plasmacytoid dendritic cells (pDCs), as well as other immune cells, express estrogen receptor alpha (ERα) [12], pDCs play an important role in SLE disease pathogenesis due to their function in mediating immune responses as well as their producing large amounts of IFN-α in response to TLR7 and TLR9 ligands [13], [14] Knockout of ERα in both control and lupus prone mouse strains resulted in reduced TLR3, TLR4, TLR7 and TLR9 responses in pDCs, spleen cells and B cells [15], suggesting that estrogen signaling affects TLR responsiveness. The gene discussed is TLR9; the disease is systemic lupus erythematosus.