IL21 and head and neck squamous cell carcinoma: Consequently, the expression of pro-inflammatory cytokines, including IFN-γ, IL-2, IL-12, and IL-21, is predominant in HPV+ HNSCC tissues, while that of anti-inflammatory cytokines, including IL-10, IL-6, and TGF-β, is increased in HPV− HNSCC tissues [133].