Since primary human CD3 + T cells activated by anti-CD3/CD28 antibody-coated beads expressed CD137 and PD-1 (Fig. 1d, Supplementary Fig. 1d), reminiscent of TILs in tumour-bearing mice (Supplementary Fig. 3f), we evaluated the binding of IBI319 to primary T cells. Here, PDCD1 is linked to neoplasm.