CD4 and head and neck squamous cell carcinoma: We found that PLAU is important for regulating immune cell infiltration in HNSCC, with particularly strong negative effects on CD8+ T cells, memory activated CD4+ T cells, follicular helper T cells, plasma B cells, memory B cells, and Tregs and positive effects on memory resting CD4+ T cells, M0 macrophages, resting mast cells, and NK cells resting.