Since inactivation of PgdA increases Listeria sensitivity to peptidoglycan-targeting antimicrobials such as lysozyme, and thus induces bacterial degradation, we measured the DNA and RNA released by EGDe and DpgdA strains following lysozyme exposure. As expected, DpgdA released significantly higher amounts of DNA and RNA than wild-type and complemented DpgdA strains, raising the possibility that both DNA and RNA could be involved in IFNb production (Fig. 8A) . We thus measured IFN-b induction in THP1 macrophages transfected with Listeria DNA, either undigested or treated with DNase. Intact but not DNase-treated DNA significantly induced IFN-b (Fig. 8B ). Macrophages were then transfected with lysozyme-digested EGDe or DpgdA, either untreated or digested with DNase. Treatment with DNase significantly reduced IFN-b production (Fig. 8C) . Taken together, these results show that Listeria DNA can induce IFN-b, strongly indicating that destruction of DpgdA bacteria intracellularly activates DNA sensors.