CD4 and neoplasm: However, CD4+ helper T cells also play a critical role in promoting CD8+ T cells’ effector function, expansion, and persistence (Kumamoto et al., 2011), and it has been shown that the presence of CD4+ T cells in the tumor microenvironment results in increased recruitment, proliferation, and function of CD8+ cytotoxic T cells (Bos and Sherman, 2010).