In addition to IRF3/7, NFkB contributes to the formation of the IFN-b enhanceosome [20, 28] . We therefore examined the involvement of the NFkB pathway by measuring induced synthesis of an NFkB-dependent mRNA. IkB is an NFkB-dependent gene and thus a read-out for NFkB activation in response to Listeria infection. We measured the induction of IkB expression in PEM infected with EGDe or the DpgdA mutant. Both strains induced IkB expression and this required internalization as treatment with dynasore reduced the level of IkB induction (Fig. 7A) . Degradation of the IkB protein was examined in PEM infected with EGDe by immunoblot using anti-IkB antibodies. IkB level was reduced rapidly after infection of wild-type PEM (Fig. S2A ). In contrast, IkB degradation was not observed in tlr2 2/2 PEM infected with Listeria (Fig. S2B ). Infection of wild-type, tlr2 2/2 and trif 2/2 macrophages with EGDe or DpgdA showed that both TLR2 and the adaptor were required for full induction of IkB mRNA in response to EGDe and DpgdA strains (Fig. 7B) . These results suggest that TLR2 and TRIF contribute to NFkB activation. The comparison between EGDe and DpgdA strains showed that both caused similar magnitudes of IkB mRNA synthesis. Thus, the activation of NFkB by Listeria is independent of PgdA, suggesting that the increased IFN-b production after infection with DpgdA relies on activation of other transcription factors such as IRFs.