CD4 and neoplasm: While cytotoxic CD8+CD45RO+ memory T cells, CD4+ T helper 1 T cells, innate cytotoxic lymphocytes, natural killer cells, natural killer T cells, and M1-type tumor-associated macrophages (TAMs) are generally considered to be anti-tumorigenic, the myeloid-derived suppressive cells, M2-type TAMs, mast cells, CD4+CD25+Foxp3+ regulatory T cells, CD4+ T helper 2 T cells, and T helper 17 cells are usually considered to be pro-tumorigenic [6,7,36].