The anti-tumor mechanisms related to the immune system include the action of cytotoxic T cells, TH1 CD4+ T cells, NK cells and M1-type macrophages, whereas tumor-promoting effects can be executed by various immune cells such as pro-tumorigenic M2 macrophage subtypes, regulatory T cells, B cells, neutrophils, and TH2 CD4+ T cells. The gene discussed is CD4; the disease is neoplasm.