Nature Immunology, Published online: 13 April 2026; doi:10.1038/s41590-026-02494-7 Chronic antigen exposure drives TOX expression in CD8+ T cells and is associated with an exhausted hypofunctional T cell state. By contrast, data now show that the function of TOX in CD4+ T cells defines the TH1 lineage and supports the effector function of these cells.
