TLR9 and infection: TLR9 is expressed dominantly in pDCs and B cells, and the unmethylated CpG motif of ssDNA is indispensable for TLR9 stimulation.51 By processing double strands DNA (dsDNA, such as chromosomal and mitochondrial DNA) into short ssDNA, DNases are essential to activate TLR9.52 Upon infection, TLR9 is critical to initiate innate immune responses via increasing proinflammatory cytokines and activating the cytotoxic NK cells and CD8+ T cells.53