Immune cell infiltration, including T cell (CD3+/CD8+/CD4+T, memory/effector T cell, and regulatory T cell), T helper 1 (TH1) cell, T helper 17 (TH17) cell, T helper 2 (TH2) cell, natural killer (NK) cell, plays a crucial role in inhibiting tumor cells or providing supports for tumor growth, and associates with a prognosis of 17 human cancers (24, 27–29). Here, CD4 is linked to cancer.