In this issue, Luff et al. (https://doi.org/10.1084/jem.20251308) show that cell-intrinsic signals from TACI drive marginal zone B cell development from T2 B cells through a mechanism involving activation of the PI3K–AKT pathway and inhibition of the FOXO1-KLF2 axis.
Guzmán et al. (2026) studied this question.