DNAM 1 is a receptor expressed by peripheral blood T lymphocytes that is involved in intercellular adhesion, lymphocyte signaling, cytotoxicity and lymphokine secretion mediated by cytotoxic T lymphocytes. DNAM 1 is broadly expressed on T cells, NK cells, platelets, monocytes and a subset of B cells. DNAM-1 is also expressed by a subset of CD3 positive thymocytes. This antibody is reported to inhibit T- and NK cell mediated cytotoxicity against tumour cell targets and to block TNF alpha and IFN gamma secretion by alloantigen-specific T-cells.