Translation factor eIF4G2 directs CD8(+) T cell lineage commitment by selectively enabling the IL-7 receptor response.

CD8(+) T cell lineage commitment in the thymus requires interleukin-7 receptor (IL-7R) signaling, but the mechanisms enabling its cytokine responsiveness are unclear. Here, we identify the translation factor eIF4G2 as an essential, selective regulator of this process. eIF4G2 expression is upregulated in double-positive thymocytes and its T cell specific deletion causes a severe post-selection blockade, specifically abolishing CD8(+) single positive thymocyte lineage commitment while sparing CD4(+) lineage choice and TCR signaling. Mechanistically, eIF4G2 deficiency ablates IL-7 responsiveness by failing to sustain the receptor γc subunit via an untranslated region dependent manner, with a concomitant impairment of IL-7Rα mRNA level. Our findings establish eIF4G2 as a pivotal translational checkpoint that licenses IL-7R signaling to enforce faithful CD8(+) T cell fate determination.