By a genetic approach we investigated the cells that are responsible for IFN-b production during murine listeriosis. We could show that IFN-b is almost exclusively produced by LysMexpressing cells in the spleen as well as in colonized lymph nodes. LysM promoter is highly expressed in monocytes/macrophages and neutrophils [44] . However, the use of the LysMcre mouse does not allow distinction between myeloid cell populations, although lower expression in CD11c + cells was reported [55] .