CD258, also known as LIGHT and tumor necrosis factor superfamily member 14 (TNFSF14), is a secreted protein of the TNF superfamily. It is a type II transmembrane protein expressed on activated T cells and immature dendritic cells and recognized by herpesvirus entry mediator (HVEM), as well as decoy receptor 3. This protein may function as a costimulatory factor for the activation of lymphoid cells and as a deterrent to infection by herpesvirus. This protein has been shown to stimulate the proliferation of T cells, trigger apoptosis of various tumor cells and block viral entry. It is also reported to prevent TNF alpha mediated apoptosis in primary hepatocyte. In addition, CD258 has been implicated in T cell development and homeostasis, dendritic cell maturation, and atherogenesis and may play a prominent role in diseases involving T cells such as graft versus host disease (GVHD) and autoimmune conditions.