Figure 1.

CD8⁺ T-cell effector and memory differentiation. Effector and memory differentiation of CD8⁺ T cells. During many acute infections, activated CD8⁺ T cells form a heterogeneous effector population with distinct developmental trajectories. The majority of activated CD8⁺ T cells acquire a terminally differentiated effector state known as terminal effector (TE) cells. After clearance of infection, most of the KLRG1⁺ cells die, while a small subset survives as long-lived TE cells. Additionally, surviving effector cells that also express IL-7Rα (CD127) seed the effector memory T-cell (Tem) pool, and some of these cells even lose KLRG1 expression and develop into various memory T-cell subsets (Herndler-Brandstetter et al. 2018). In contrast, a smaller fraction of effector cells differentiates into memory precursor (MP) cells, which encompass the greatest potential to develop into long-lived memory cells and are characterized by increased amounts of CD127 (Kaech et al. 2003). After resolution of infection, the MP cells seed most of the memory pool, giving rise to the various memory T-cell subsets (Tem, Tcm, Tpm, and Trm).