TOX and infection: Mice infected with high-affinity VSV-N4 had a large shift in the frequency of TOX+ precursors and effectors at seven days after infection, whereas mice infected with VSV-V4 had little to no TOX+ expression in either the precursors or the effector compartment (Fig. 5a,b), indicating that the formation of Tpex in acute infections depends on receiving strong TCR signals.