PDCD1 and head and neck squamous cell carcinoma: After one week of anti-PD-1 treatment, lymph node cells of the lesion-bearing mice secreted higher levels of IFN-γ in response to premalignant (p < 0.001) or HNSCC (p < 0.01) challenges compared to their IFN-γ production in response to a challenge of normal tongue epithelium.