Peripheral Treg of HNSCC patients also displayed significantly elevated levels of the immune checkpoints CD137 (mean value 0.8 ± 0.8% versus 0.4 ± 0.3% healthy controls), while the expression of OX40 on Treg was unchanged (Figure 2C,D). Here, TNFRSF9 is linked to head and neck squamous cell carcinoma.