CD226/DNAM-1 (DNAX accessory molecule-1) is a 65 kDa type I transmembrane glycoprotein expressed on the majority of T cells, NK cells, monocytes, and a subset of B-cells. A soluble form (50 kDa) of CD226 is present in normal serum and the supernatant of cultured activated T cells. Ligand binding to CD226 results in phosphorylation of Ser329 and Tyr322, suggesting a role in signal transduction. CD226 acts as an adhesion molecule involved in the binding of certain tumor cells to CTL and NK cells and mediates their cytotoxicity. CD226 also stimulates TNF-α and IFN-γ secretion by alloantigen-specific T cells.Synonyms: DNAM-1, DNAX accessory molecule 1