PDCD1 and neoplasm: Upon clearance of antigen, these cells exhibit an epigenetic profile distinct from either Teff-cells or Tem-cells, suggesting that while anti-PD-1 ICB transiently induces an anti-tumour effector phenotype it does so within the epigenetic landscape of an exhausted cell with little flexibility to differentiate long term in the presence of anti-PD-1 antibody [13].