Type 1 T cells promote the generation of CD8 tissue-resident memory T cells.

Tissue-resident memory T (T) cells, functionally distinct from circulating memory T cells, have a critical role in protective immunity in tissues, are more efficacious when elicited after vaccination and yield more effective antitumor immunity, yet the signals that direct development of T cells are incompletely understood. Here we show that type 1 regulatory T (T) cells, which express the transcription factor T-bet, promote the generation of CD8 T cells. The absence of T-bet-expressing type 1 T cells reduces the presence of T cells in multiple tissues and increases pathogen burden upon infectious challenge. Using infection models, we show that type 1 T cells are specifically recruited to local inflammatory sites via the chemokine receptor CXCR3. Close proximity with effector CD8 T cells and T cell expression of integrin-β8 endows the bioavailability of transforming growth factor-β in the microenvironment, thereby promoting the generation of CD8 T cells.