To determine whether the dramatic reduction of pDC IFN-a/b production by NK cell functions in Klra8 mice could in part account for the ability of these mice to preserve an intact cDC compartment and to mount early CD8 T cell responses, we examined whether exogenous administration of the cytokines in these animals could directly impact the initiation of cDC and CD8 T cell responses despite efficient NK cell-mediated control of viral load. MCMV-infected Klra8 mice were treated with recombinant mouse IFN-a as described in Materials and Methods, and their DC or CD8 T cell compartments were compared to those of controltreated Klra8 and BALB/c mice ( Figure 6A ). The treatment of Klra8 mice with IFN-a indeed led to a drastic reduction in both CD11b and CD8a splenic cDCs, but not in pDCs, when compared to their control-treated Klra8 counterparts. Likewise, IFN-a treatment induced a delay in the expansion of total, CD43 hi , and IE-1 Tet þ CD8 T cell numbers ( Figure 6B ).