In response to intracellular pathogens, CD8 + T cells are activated to proliferate and differentiate into a heterogeneous population of effector T cells, which are armed to eliminate infected cells. After pathogen clearance, the majority of effector CD8 + T cells die; however, a subset survives and differentiates to long-lived memory T cells. Should reinfection occur, these memory cells undergo rapid expansion and redifferentiation into effector cells, providing superior protection compared with naive T cells and protecting the host for decades in many cases (Harty and Badovinac, 2008). The ability to selectively induce T cell memory would provide novel methods for provoking protective immunity and inform vaccine strategies.Identification of effector and memory precursor CD8 + T cells within the effector population is facilitated by their distinct expression of several surface receptors. Both subsets express high levels of CD44, whereas IL-7-receptor-α (CD127) is selectively up-regulated during the transition to long-lived memory cells (Kaech et al., 2003). Killer cell lectin-like receptor G1 (KLRG1) expression is inversely correlated with CD127 expression (Joshi et al., 2007) and identifies, in both mice and humans, a subset of terminally differentiated effector cells that possess limited proliferative potential and a shorter lifespan (Voehringer et al., 2002;Joshi et al., 2007).ZEB2 is a multi-zinc-finger transcription factor known to play a significant role in early neurogenesis and in epithelial-mesenchymal transition-dependent tumor metastasis. Although the function of ZEB2 in T lymphocytes is unknown, activity of the closely related family member ZEB1 has been implicated in lymphocyte development. Here, we find that ZEB2 expression is up-regulated by activated T cells, specifically in the KLRG1 hi effector CD8 + T cell subset. Loss of ZEB2 expression results in a significant loss of antigen-specific CD8 + T cells after primary and secondary infection with a severe impairment in the generation of the KLRG1 hi effector memory cell population. We show that ZEB2, which can bind DNA at tandem, consensus E-box sites, regulates gene expression of several E-protein targets and may directly repress Il7r and Il2 in CD8 + T cells responding to infection. Furthermore, we find that T-bet binds to highly conserved T-box sites in the Zeb2 gene and that T-bet and ZEB2 regulate similar gene expression programs in effector T cells, suggesting that T-bet acts upstream and through regulation of ZEB2. Collectively, we place ZEB2 in a larger transcriptional network that is responsible for the balance between terminal differentiation and formation of memory CD8 + T cells. Thus, differential expression of CD127 and KLRG1 identifies two populations of T cells during the peak of an infection: KLRG1 hi CD127 lo cells that consist of shorter-lived effector and effector memory cells and KLRG1 lo CD127 hi effector cells that include the long-lived memory precursors (Kaech and Wherry, 2007;Kallies, 2008). Notably, both populations under...