IFNB1 and infection: To gain further insight into the innate immune response elicited upon infection with the various LTA mutants, BMD macrophage cells were infected with ΔlafA, ΔlafB, ΔlafC, and ΔltaP mutants in WT or the ΔmarR background, and IFN-β, IL-6 (which is also part of the type I interferon response to L. monocytogenes infection) and TNF-α transcript levels were analyzed at 6 h.p.i. using RT-qPCR.