CD4 and head and neck squamous cell carcinoma: The higher infiltration level of Tregs in low-risk group may appear contradictory to their immunosuppressive nature, whereas the tumor infiltration by FOXP3+CD4+ Tregs is found to be positively correlated with better locoregional control of the head and neck cancer (Badoual et al., 2006) and the high Tregs fraction has a positive correlation with good prognosis in HNSCC (Cillo et al., 2020).