Using these genetically modified mice, we highlight the importance of IFN-b during the deleterious action of type I IFN in the course of Listeria infection. In addition, the novel reporter mice revealed a maximum of IFN-b induction 24 hours post infection (p.i.) in spleen and, surprisingly, 48 hours p.i. in cervical and inguinal lymph nodes after high dose intravenous infection. Low dose infection followed the same pattern of IFN-b production, although with delayed kinetics. The luciferase signal in spleen and lymph nodes mirrored the presence of Listeria in these organs. Moreover, our results showed that LysM-expressing cells are the main producers of IFN-b during murine listeriosis, especially the cells previously defined as Tip-DCs. Finally, neutrophils, DCs and pDCs and did not significantly contribute to type I IFN production under our conditions of L. monocytogenes infection.