CD4 and neoplasm: CD4+ T regulatory cells, type 2 CD4+ T lymphocytes, type 2 natural killer T cells, myeloid-derived suppressor cells, M2 or tumor-associated macrophages, B cells, and possibly mast cells promote tumor progression, while CD8+ T lymphocytes, type 1 CD4+ T lymphocytes, natural killer, type 1 natural killer T cells, M1 macrophages, and immune killer dendritic cells promote tumor destruction (Ostrand-Rosenberg, 2008).