TLR9 and brain edema: In acetaminophen-induced ALF, DNA fragments released by apoptotic hepatocytes have been shown to be responsible for the activation of TLR9 and induction of systemic inflammation.16, 28 These findings support the results of our recent human study, which showed profound TLR9 activation in neutrophils in the presence of plasma DNA in patients with acetaminophen-induced ALF, systemic inflammation, and brain edema,17 suggesting that TLR9 mediates the ammonia-induced brain edema in a DNA-driven manner.