IFNAR1 and infection: Addition of recombinant type I IFN on day 1 and 2 during MCMV-IE2-GP33 infection in mice that received Ifnar1+/+ and Ifnar1−/− P14 cells, caused no significant increase in the expansion of the P14 cells either transferred in WT or Cd80/86−/− mice, indicating that additional type I IFN signaling has negligible impact on B7-mediated signals that drive T cell expansion in MCMV infection (Figure 5F).