PDCD1 and diabetes mellitus: The pathogenesis of ICI-DM remains unclear, although it predominantly occurs in patients receiving PD-1/PD-L1 inhibitors, with the highest incidence observed in combination therapies, such as PD-1 plus CTLA-4 blockade.[10] PD-1, expressed on T lymphocytes, macrophages, natural killer cells, and dendritic cells, mediates immunosuppression by binding to its ligands PD-L1 (B7-H1/CD274) and PD-L2 (B7-DC/CD273).