other times points examined, in Klra8 mice as compared to BALB/c mice ( Figure 1A) . The serum levels of other innate cytokines were also significantly lower in Klra8 mice, including IL-12p70 ( Figure 1A ) and TNF-a (unpublished). Similar results were observed when comparing serum cytokine levels between control-treated and NK cell-depleted Klra8 mice ( Figure S2 and unpublished data). Thus, while the systemic production of IFN-a/b and of other innate cytokines in response to MCMV infection is very high in susceptible animals, it is greatly reduced in the presence of an NK cell response that controls viral replication early and efficiently.