CD4 and head and neck squamous cell carcinoma: It is hypothesized that a low CD4+ T-cell count, even a CD4+ T-cell count around 300 cells/μL, and even around 350 cells/μL in some cases, increases the risk of progression to HNSCC partially because reactivation or reacquisition of oral HPV infection, more than a reduced clearance [68, 69, 87, 89].