Intravenously inoculated L. monocytogenes is taken up by the spleen and removed from the blood predominantly by mononuclear phagocytes in the marginal zone of the white pulp [23] . Myeloid cells, especially monocytes and macrophages are rapidly recruited to sites of bacterial infection and are required for initial control of L. monocytogenes infection [11, [24] [25] [26] . During bacterial infections, circulating monocytes are known to differentiate into tissue macrophages and dendritic cells (DCs) [27] . Additionally, inflammatory Gr1 + /Ly6C high monocytes are able to differentiate into tumor necrosis factor-a (TNF-a) and inducible nitric oxide synthase (iNOS) producing so-called Tip-DCs at sites of infection [11] .