Slow-cooked naive T cells make better effectors.

While the TCR diversity of naive T cells is well established, the extent of their functional heterogeneity remains largely uncharted. In this issue of JEM, Sajiki et al. (https://doi.org/10.1084/jem.20252076) demonstrate that long-lived naive CD8 T cells accrue tonic TCR signaling during homeostasis, driving their differentiation into functionally superior effectors.