The RIK-2 monoclonal antibody specifically binds to CD253, also known as TRAIL (TNF-Related Apoptosis-Inducing Ligand) and Apo2 ligand (APO-2L). CD253 is a member of the Tumor Necrosis Factor Superfamily and is encoded by the TNFSF10 gene. CD253 is a type II membrane protein that may be expressed as a soluble as well as full-length, cell surface-associated protein. Both surface and soluble forms of TRAIL rapidly induce apoptosis in a wide range of tumor cell lines but not normal tissue. TRAIL is expressed by activated T cells, NK cells, dendritic cells, monocytes and a variety of non-lymphoid cells. TRAIL can bind to and exert apoptosis through DR4 (TRAIL-R1) and DR5 (TRAIL-R2) receptors. It can also bind to decoy receptors, including DcR1/TRID/TRAIL-R3 and DcR2/TRUNDD/TRAIL-R4, and possibly OPG/TNFRSF11B, which may serve to regulate TRAIL activity. TRAIL has been shown to be involved in T cell-mediated cytotoxicity, but its mechanism of action remains to be fully elucidated. The RIK-2 clone was selected based on its ability to block TRAIL-mediated cytotoxic activity.