Chronic exposure to tumour antigens and inflammatory conditions in the TME can promote CD8+ T cell dysfunction (also known as exhaustion), a terminally differentiated state characterized by reduced proliferative capacity, impaired cytokine production and increased expression of inhibitory receptors (that is, PD1, LAG3, TIM3) that limit T cell effector function5,6. This evidence concerns the gene PDCD1 and neoplasm.