PDCD1 and neoplasm: Sintilimab has unique binding epitopes on PD-1, and the PD-1/PD-L1 axis has recently emerged as a novel target for immunotherapy in cancer treatment.11 By binding to PD-1, sintilimab blocks the interaction between PD-1 and its ligands PD-L1 and PD-L2, resolves immune suppression, enhances T cell-mediated immune surveillance, and inhibits tumor cell proliferation, thus achieving effective disease control.12 T cell subsets play an essential role in cellular immune response.