To discriminate between these options, we took advantage of the fact that in our acute infection model with transferred P14 CD8 T cells mice were virus-free on day 8 but showed high expression of Eomes in P14 Tbx21E/E CD8 T cells in contrast to P14 Tbx21+/+ CD8 T cells, which, reciprocally, showed high expression of T-bet. Here, EOMES is linked to infection.