CD274 and head and neck squamous cell carcinoma: In summary, the results of this study further revealed the complex nature of wt sequence p53 peptide-specific immune responses in HNSCC patients and highlight several new parameters, like naïve T cell activation by vaccination and checkpoint inhibition by modulating the PD-1/PD-L1 axis, that should be considered in developing the design and analysis of future vaccination protocols to enhance the efficacy of p53-based immunotherapy of HNSCC.