In response to a viral infection, pDCs can recognize viruses through toll-like receptor 7 (TLR7) and toll-like receptor 9 (TLR9) signaling and rapidly produce type I interferons (IFNs), which can lead to robust CD8+ T cell activation and increase antigen presentation on DCs [48,49,50,51]. The gene discussed is TLR9; the disease is viral infectious disease.