CD4 and head and neck squamous cell carcinoma: Previous studies revealed that CD8+ T cells (Mandal et al., 2016; Spector et al., 2019), mast cells (Cheng et al., 2021), NK cells (Bisheshar et al., 2020), TILs (Spector et al., 2019), and CD4+ follicular helper T cells (Cillo et al., 2020) have been shown to have a positive role in antitumor immunity and prognosis of HNSCC.