TOX and cancer: Indeed, proliferating CD8+TCF1+T cells showed significantly higher levels of all key activation markers (TOX, PD-1, GZMB, ICOS, Helios; Extended Data Fig. 10d) and were more often in contact with cancer cells (Extended Data Fig. 10e,f) and with MHCII+ cells, in keeping with past reports that these stem-like T cells reside in MHCII+ niches19 (Extended Data Fig. 10g).