CD4 and head and neck squamous cell carcinoma: Similarly, circulating CD8+ Teffs or CD4+ Tems were also found to be associated with a favorable response to ICI therapy in various tumor types.48–51 Notably, CD8+ Tems and CD4+ Tcms were thought to be associated with good prognosis in head and neck squamous cell carcinoma and gastric cancer patients51,52; however, these findings were related to unfavorable outcomes in PC patients.