MAPK8 and viral infectious disease: Member of the TNF ligand family; binds to several members of TNF receptor superfamily; induces apoptosis in transformed and tumor cells triggering activation of MAPK8/JNK, caspase 8, and caspase 3; plays a role as an effector molecule in NK cell tumoricidal activity; implicated in immunosuppressive, immunoregulatory and immune-effector functions; plays a role in immune response to viral infections and tumor immune surveillance