CD8A and head and neck squamous cell carcinoma: Among them, immune cells such as B cells, CD8+ T cells, Th1 cells, TILs, and immune pathways such as APC-co-stimulation, cytolytic activity, MHC class I, and T-cell-co-stimulation play an inhibitory role in the occurrence and development of HNSCC [36,39,40,41,42,43,44].