Moreover, tumor infiltrating leukocytes, including macrophages (7, 8), regulatory T cells (Tregs) with CD4+/CD25+ phenotype and suppressive function on helper and effector T cells (9), as well as a heterogeneous group of similarly acting myeloid-derived suppressor cells (MDSCs) (10), can cooperate in antagonizing the protective immune response while favoring tumor growth. This evidence concerns the gene CD4 and neoplasm.