CD8A and head and neck squamous cell carcinoma: Indeed, although higher numbers of CD8+ T lymphocytes have been correlated with improved outcomes of HNSCC by some authors (144–146), often T cells present in HNSCC microenvironment are dysfunctional or “exhausted.” In this regard, high numbers of immunosuppressive Tregs are found among tumor infiltrating lymphocytes in HNSCC, and their presence has been associated with unfavorable prognosis and resistance to radiotherapy (147).