CD4 and head and neck squamous cell carcinoma: For instance, CD4+/CD25high/Foxp3+ Treg cells secreted IL-10/TGFβ1 to inhibit TME [210]; Neutropolin-1-/- Treg cells produced Interferon-γ triggering Neutropolin-1+/+ Treg cell fragility to modulate TME immune activity [211]; HNSCC cells target Th17+ cells for an increased Cox2 expression, resulting in greater tumor cell growth [212]; TAMs enhanced HNSCC invasiveness and lymph node metastasis via IL-33 and the CCR4/CCL22 axis, respectively [213,214]; and immunosuppressive adenosine (ADO) is reduced in HNSCC patients compared with healthy control subjects [215].