By contrast, infection with the PA14 ΔpopB mutant showed significant reductions (~ 4-fold) in expression of tlr4, tlr5, nlrc4, and il-18 genes (P < 0.05) compared to PA14 wild-type, but not significantly different for casp-4 and il-1β genes (P > 0.05). Here, TLR4 is linked to infection.