CD4 and neoplasm: The suppressive factors in the tumor microenvironment might include cellular components, such as CD4+ regulatory T cells (4, 5), CD8+ regulatory T cells (6), Th17 cells (7), Kupffer cells (8), myeloid-derived suppressor cells (9, 10), and humoral components, such as IL-10 (11), TGF-β (12), and amphiregulin (13).