Cancer cells can express ligands for T cell inhibitory receptors such as PDCD1 (PD-1) (ligand is CD274 [PD- L1]), CTLA-4 (ligands are CD80 and CD86), and HAVCR2 (aka TIM3) (ligand reported to be GAL9) to inhibit T cell activation and cytolytic T cell responses. Here, PDCD1 is linked to cancer.