CD4 and head and neck squamous cell carcinoma: HNSCC patients mainly have decreased clusters of differentiation (CD)3+, CD4+, and CD8+ T cell levels, which worsens the prognosis.[14] Oncolytic viruses activate the immune response against the tumor by entering and infecting the tumor cells and releasing tumor-associated antigens, pathogen-associated molecular patterns, and cellular danger-associated molecular patterns.