These include programmed death cell protein 1 (PD‐1) (primarily expressed on T‐cells), programmed death‐ligand 1 (PD‐L1) (expressed on APCs, other immune cells and tumour cells), and cytotoxic T‐lymphocyte‐associated protein 4 (CTLA‐4) (primarily expressed on T‐cells).34, 35. The gene discussed is PDCD1; the disease is neoplasm.