At the same time, with the introduction of the concept of immune checkpoints, a series of inhibitory immune checkpoints including PD-1, CTLA-4, TIM-3, IDO, KIR, and TIGIT, have been proved to be involved in the construction of HNSCC immunosuppressive microenvironment (8). This evidence concerns the gene PDCD1 and head and neck squamous cell carcinoma.