Monoclonal antibody TX25 recognizes human DNAX accessory molecule-1 (DNAM-1; CD226). This is a 65 kDa type I transmembrane glycoprotein and a member of the immunoglobulin superfamily. DNAM-1 is constitutively expressed on a majority of T cells, NK cells and macrophages. Interaction of DNAM-1 with DNAM-1 ligands CD155 and CD112 induces intercellular adhesion, infiltration and cell signaling, resulting in a variety of cellular responses including innate and adaptive immunities. DNAM-1 consist of a leader sequence, extracellular domain transmembrane domain and a cytoplasmic domain. DNAM-1 is predominantly known for its NK dependent antitumor immunity. However there is an emerging role in the immune response in viral infections. In that way, DNAM-1 expression has been noted on NK cells of patients with chronic pathogen infection such as HIV and tuberculosis. Ligands for DNAM-1 are poliovirus receptor and nectin-2. Upregulation of these receptors can be found on eg epithelial and endothelial cells in response to cellular stress and in some tumors. The activation signal after ligand binding depends on association of DNAM-1 with LFA1 integrin. DNAM-1 related NK cell activity is counterbalanced by the inhibitory receptors CD96 and TIGIT. These receptors bind to the same ligands but have apposing effects. There has also been found a soluble variant of the receptor (sDNAM-1). There are some indications this can be used to evaluate the development of GVHD.