We have therefore demonstrated that TLR9 is necessary for the development of ammonia-induced brain edema.16, 29 The observation that systemic inflammation and brain edema can be prevented following administration of a TLR9 antagonist supports the exploration of TLR9 antagonism as a therapeutic modality in early ALF to prevent the progression to intracranial hypertension. This evidence concerns the gene TLR9 and edema.