CD8A and neoplasm: These gut-educated ex-T<sub>H</sub>17 cells produce high levels of the pro-inflammatory cytokines interferon (IFN)-γ and tumour necrosis factor (TNF) within the tumour microenvironment (TME), enhancing antigen presentation and promoting recruitment, expansion and effector functions of CD8<sup>+</sup> tumour-infiltrating cytotoxic lymphocytes and thereby enabling anti-PD-1-mediated tumour control.