LIGHT, also known as TNFSF14, is a homotrimeric glycoprotein in the TNF superfamily. It is expressed on the surface of activated lymphocytes, NK cells, immature dendritic cells, monocytes, and granulocytes. A soluble form can be shed by proteolysis. LIGHT binds and activates HVEM/TNFRSF14 to costimulate Th1 immune responses, enhance CD8+ T cellâmediated tumor immunity, and regulate allogeneic T cell activation and allograft rejection. In addition, it binds and activates Lymphotoxin beta R/TNFRSF3 to induce apoptosis, cytokine production, mesenteric lymph node organogenesis, and maintenance of lymph node structure and function. It can also bind the soluble human decoy receptor DcR3/TNFRSF6B.