While a similar degree of sensitization occurred in the PR8-infected, Sp3-infected WT and IFN-β-deficient mice, there was an ∼4-day delay in the mean time to death in the IFN-β−/− mice (P = 0.008), supporting the notion that type I IFNs, such as IFN-β, are detrimental to the host during 2° bacterial infection. Here, SP3 is linked to bacterial infectious disease.