The cytotoxic T lymphocytes (CTLs, also CD8+ T cells, marked as CD3+CD8+ T cells) are pivotal immune cells directed against tumor cells susceptible to cell lysis, but CD4+Foxp3+ regulatory T cells (Treg) disturb antitumor immunity by suppressing the activities of effector T cells. The gene discussed is FOXP3; the disease is neoplasm.