According to recent publications, different myeloid cell populations were shown to be responsible for IFN-b production during Listeria infection. Stockinger et al. defined CD11b + CD11c 2 PDCA1 2 B220 2 macrophages to be the major IFN-b producers and pDCs were claimed to make no contribution [28] . On the other hand, Dresing et al. observed IFN-b exclusively in the myeloid cell population called Tip-DCs [29] . In the present study, we used a genetic approach to address the question which cells produce IFN-b during experimental listeriosis.