CD4 and neoplasm: The study of the mechanisms of tumor cell death under the action of cytotoxic T lymphocytes allowed us to establish that Tag7 exposed on the cell surface of CD4+-T lymphocytes can interact with Hsp70 on the surface of a tumor cell and ensure the binding of a lymphocyte to a target cell with subsequent induction of cell death due to the interaction of the FasL lymphocyte with the Fas receptor of a tumor cell [12].