CD4 and head and neck squamous cell carcinoma: In terms of cell abundance, it was found that FOXP3+ CD4+ regulatory T cells (Tregs) and CD8+ T cells are positively associated with patient prognosis in a cohort of patients with mixed human papillomavirus–positive/negative (HPV+/HPV−) head and neck squamous cell carcinoma (HNSCC; ref. 1).