TLR9 and systemic inflammatory response syndrome: As nuclear factor-κB (NF-κB) regulates the expression of several pro-inflammatory cytokine genes (24) and is highly activated in inflammatory diseases (e.g., rheumatoid arthritis, asthma, inflammatory bowel disease and SIRS) (25), we hypothesized that mtDNA can induce NF-κB activity through TLR9.