TNFRSF9 and head and neck squamous cell carcinoma: As shown in Fig. 1A, the percentage of total Treg cells did not affect the response to pembrolizumab treatment at baseline, as well as the frequency of different Treg subsets (resting, active, ns, and CD137+) (Fig. 1B), indicating that at baseline, Treg cells do not influence the response to treatment in (R/M) HNSCC patients’ setting.